Integrated Pest Management Manual
While many species of insects damage turfgrass in the United States, this package describes in detail the life histories and management of those which have been found to be frequent problems within the National Park System. Photographs and further information concerning these and other turf pests can be found in publications such as Niemczyk (1981), Daley (1975), Shetlar (1982), Converse (1982), or Tashiro (1987).
MONITORING FOR TURF INSECTS
This section discusses monitoring techniques and strategies applicable to all turf insects. Information on monitoring and thresholds for specific turf pests is given in the section of this module that deals with that pest. Most detection and sampling methods can be classified as either active or passive techniques. Both have the capability to help in predicting pest problems or quantifying existing damage and pest infestations. The most popular and efficient active sampling method involves visual inspections (scouting). Passive systems use either light, pheromone, or mechanical traps that require fewer site visits per season. The trade-off between visual and passive systems is accuracy. Traps will tell you if an adult insect is present in the sampling area, but will not show if it is causing injury or how extensive the population is. These can usually only be determined by some type of visual inspection. The best monitoring program combines both visual inspections and a variety of passive methods.
Regardless of the sampling methods used, the trade-off becomes time for accuracy v. cost. Scouting cost and time can be reduced and accuracy maintained if monitoring is concentrated on key pests in key locations. Key pests are those responsible for major turf losses at a particular site. Key locations reflect the behavior of the key pest to habitually select and damage the same turf areas over time. For example, Japanese beetles are most likely to be found in turf areas which receive full sun, so these areas are considered key locations for Japanese beetles. Key areas are sites that are unique because of aesthetics, rarity of plant material, or historic value. These areas may require lower damage thresholds to meet the expectations of visitors.
Monitoring Based on Key Locations
Predetermined key locations should be intensely monitored to detect the first occurrence or first damage. Many turf insect pests require warm, moderately-dry turf conditions for optimal development. For example, chinch bugs prefer the full sunlight of southern and eastern exposures. Japanese beetle adults lay more eggs in well- watered, sunlit turf areas as compared to dry areas, and billbugs will lay more eggs close to driveways and sidewalks than in the open turf. In southern regions areas first damaged by migrant adult mole crickets in the spring will become the most severely damaged in late summer. These examples demonstrate the need for understanding the biology and behavior of turf pests in relation to the site.
Other key locations that require special monitoring are areas regularly infested every year. Accurate records, or an experienced manager's memory, are important in identifying these areas. If historical documentation is unavailable, pest damage, site, weather, and turf characteristics must be correlated. Over time these sites will become evident. This type of detailed factual record-keeping will help you select the appropriate management tactics. Once a key site is identified, modification of the habitat or vegetation can reduce the reinfestation problem and, in the long-term, reduce pesticide usage. In many situations the elimination of turfgrass or replacement with a better adapted turfgrass species will solve the problem.
These methods are the quickest, most accurate, and most frequently used technique for detection of turf insect problems. The observer, however, must have a wide background or training in turf management, disease management, and insect pest management in order to make the correct diagnoses. Detection of insect damage or the prediction of pest outbreaks also depends on repeated observation of insect adult activity as well as recognizing small changes in plant appearance that are diagnostic of pest injury. The frequency of scouting visits depends on the pest complex, visitor expectations, thresholds, and costs. Typically a weekly or bimonthly schedule in spring and summer is sufficient, while a monthly schedule is acceptable after mid- August into the fall. The following examples show situations and conditions where direct observations are essential to a successful integrated pest management program.
Spot sampling. Trained individuals can quickly make accurate observations and pest counts. A 30-second spot count per square foot sample in 20 or so turf locations should provide information on the scope of damage, stages of pest present, and population estimates. Spot counts require searching the thatch and root zone thoroughly. All pest species can be detected with this method. Although accurate, visual inspections only reflect a population response to the environmental and site conditions at one point in time. For example, the weather may be cool or excessively wet at the time of sampling. These conditions tend to slow down insect development, daily movements, and response to flushing agents. Generally samples taken under extremes in temperature and moisture tend to underestimate populations. This can be avoided by increasing the number of sample dates each month or avoiding sampling during weather extremes. Supplemental sampling with traps should provide a better population estimate because the counts reflect an average over longer periods of time. Traps collect samples every day regardless of environmental conditions, personal discomfort, and human variability. Scouting is usually done during the daylight hours but during hot weather insects may not be active until late evening so traps may alert you to unseen problems. If a problem is identified via a spot count, one of the following methods will provide a better estimate of threshold populations than spot sampling.
Irritant sampling. This method is more accurate than the 30 second spot counts, particularly where insects are hidden in thick thatch or cracks in the soil. The irritants are only recommended for sampling highly mobile insect pests (Niemczyk 1981). Irritants will not expose soil pests such as white grubs and billbug larvae. It is most effective when turf is mowed or clipped before making observations.
Species living in the thatch such as sod webworms, cutworms, chinch bugs, and billbug adults respond to irritant agents. Flushing mole crickets from the soil is also possible, but accuracy may diminished due to of variations in thatch thickness, soil temperature, soil moisture, and depth of feeding activity. To flush with soap in non- thatch situations, use 1 ounce of liquid detergent in 1 gallon of water per yd2.
Use of the irritant method requires both a through soaking of the thatch layer or soil and close observation in order to detect the excited insects. Most insects will exit the thatch within five to six minutes and move out of the sample area quickly. One person may have difficulty observing this activity over an area of 1 yd2; the area can be reduced to 2 ft2 if necessary. To take an irritant sample, a circular metal retaining frame which is 27" across by 6" high is forced into the soil through the thatch layer and filled with 4 ounces of liquid detergent in 4 gallons of water. Count the number of insects which float to the top after ten minutes.
Flotation sampling. This is used primarily for estimating chinch bug populations. A 1 or 2 pound open-ended coffee can or a specially-made cylinder with handles is forced into the soil through the thatch layer and 3"-4" inches of water poured inside. If the water recedes more water must be added to maintain that level. All stages of the chinch bug, as well as the principal predators such as the big-eyed bug, should float to the surface within 5-10 minutes.
Although very accurate, flotation sampling is also time-consuming. This method confirms chinch bug infestations or determines the extent and population density of infestations.
Soil sampling. Although the most difficult and time-consuming of all the visual sampling methods used in turf monitoring, soil sampling provides the most accurate method for determining white grub and billbug larval population densities. Samples are initially taken in areas where turf insects have been or are expected to be a problem, including sunny areas with adequate moisture, areas where insect damage is visible, and areas where previous treatment was needed. The location and severity of grub infestations are detected by a circular sampling pattern. Once areas of grub infestation are located, samples are taken in a circular pattern which expands out from the initial site. Continue to sample outward from the initial site until grub counts become low enough to no longer be a concern.
The 1 square foot sod spade method is the least destructive but most time- consuming way to sample turf. A 1 ft2 sample is cut on three sides to a depth of 3" to 4" and the sod square is folded back to expose the soil. The soil is then broken apart, the grubs counted, and the soil returned to the hole. The grub counts are recorded and the sod flap is returned on top of the loose soil. This method is more accurate than the sod cutter but many samples are required for a good population estimate. Adjustments in the depth of cut can be made in the fall and spring when grubs are more widely distributed throughout the soil profile.
A standard golf course cup cutter allows more samples to be taken, increasing the sampling accuracy relative to the spade technique. The standard cup cutter is 4.25" in diameter; this one-cup cutter grub count can be converted to a square foot basis by multiplying by 10.15. Begin by taking soil cores to a depth of 3"-4" at key locations; do more extensive sampling if grub activity is detected.
A sod cutter produces the quickest soil sample. During the summer and early fall, population estimates are made by removing a series of 1"-2" thick sod slabs and counting the unearthed grubs. Unfortunately some grubs will be missed if they feed at the thatch level or well below the 2"-3" level, particularly species that move rapidly up and down in the soil profile in response to moisture, such as the European chafer, green June beetle, and oriental beetle. This method is less accurate in the late fall and early spring because grubs are moving up and down in the soil profile.
Passive Sampling Techniques
Light traps, mechanical traps, and pheromone traps are best used in a park-wide integrated pest management program. Although less accurate than the visual method, these traps are still useful in monitoring a pest's presence, especially yearly and seasonal population fluctuations. They also aid in scheduling peak scouting activities.
Blacklight traps. These systems can collect large numbers of sod webworm and white grub adults. To date there is no way of estimating the damage potential or the resulting larval population from these adult counts, but information on adult activity obtained from these traps is useful in determining when larvae will be active. The high cost of $200-$300 per trap often makes this option prohibitively expensive.
These traps will also provide notice of the first occurrence of a pest and delineate the species distribution over a large geographic area. Determining the relative abundance of species and risk assessment of damage from one year to another at the same sampling site is another important use of light traps.
Pheromone traps. Pheromones are chemicals which are emitted by an organism to communicate with other members of its species. The most widely used pheromone trap in turf integrated pest management programs is the Japanese beetle trap. This trap uses a floral lure and female sex pheromone. The high price per trap and the excessive number required per acre to significantly reduce the adult beetle populations limits the use of trapping of beetles as a management tactic. Trapping can be used as a monitoring tool to detect the buildup of populations and to monitor variations in populations between geographic locations or from one year to the next. Most Japanese beetle traps utilize both the floral and sex pheromone lures. The sex lure increases the number of male beetles collected by 10-40%. The traps should be used without the sex lure component when they are used for population monitoring so trap catches will more accurately reflect the normal 50:50 sex ratio. Monitoring the females is more important because they lay the eggs that give rise to the damaging grub population. Additionally, some parasites that attack the adult beetle, such as the Winsome fly (Istocheta aldrichi), can be easily collected from trapped adult beetles and distributed into new communities or geographic locations.
Daily beetle trap catches will be strongly influenced by temperature, rain, distance from host plants, soil type, groundwater levels, and natural enemies. Using several traps at each sampling location will help reduce the effect of this variability on population estimates.
Pheromones for several other species of annual white grubs are now being tested and should be on the market within a few years. Otherwise, lures for species such as black cutworm, true armyworm, and fall armyworm are now available for use. Unfortunately, little progress is being made on the sod webworm species other than the cranberry girdler, Chrysoteuchia topiaria (Zell). This sampling tool will become more important in the near future when additional pheromone systems are marketed for turf insects.
Pitfall traps. These are primarily used to monitor billbugs, mole crickets, chinch bugs, and other highly mobile arthropods. The basic design is a small hole or pit lined with a slippery-sided container with the bottom filled with a killing liquid such as soapy water or alcohol. Small pin holes should be punched into the bottom of all the cups to allow water drainage. Although the trap-line setup takes time, daily, season-long inspection is quick. This trap is best utilized for monitoring of first occurrence for the length of the adult activity period.
Data collected from insect traps becomes more meaningful if used in conjunction with degree-day heat unit life history models. These models measure the amount of heat over a certain minimum temperature (usually 50
Additional Benefits of Monitoring
Prediction of outbreaks. Regardless of the monitoring method, observations of adult activity of turf insect pests can help in predicting problems. High populations infer high risk of damage later in the season. Generally, adult females will be active and laying eggs two to four weeks before the immature stages start to cause noticeable damage. For example, if one billbug adult is observed per minute of observation, sufficient egg-laying and subsequent larval damage will occur that may require preventative treatments (Niemczyk, 1981). Observations in Ohio (D. Shetlar pers. comm.) showed that if billbug pitfall traps caught two to five adults per day during the peak egg-laying period, moderate turf injury could result in July. More severe losses could occur if counts exceed seven to ten per day over several days.
Outbreak detections in adjacent sites. Detection of injury or pest activity in areas adjacent to the key location may indicate that these areas run increased risk of developing a problem in the future. These key locations should be monitored more frequently than other key locations. This often occurs with chinch bugs and billbugs, since they rarely fly but tend instead to walk slowly from one area to another.
ANNUAL WHITE GRUB SPECIES COMPLEX
White grubs are the larvae of many species of beetles, most of which belong to the family Scarabaeidae. Although the adults differ from one another in appearance and life cycles, the grub stage of all species are similar in appearance. Fully grown larvae are 1/2" to 3/4" long, white to grayish, with brown heads and six legs. Refer to Tashiro (1987) to see the relative sizes of grubs. They generally assume a C-shaped position while in the soil. Grubs can be identified to species on the basis of the raster setal hair pattern found on the underside of the last abdominal segment. These are illustrated in Tashiro (1987). The raster is easily seen using a 10x magnifier.
Although numerous species of grubs cause turf damage, five key species are described in detail in this module; the Japanese beetle, northern and southern masked chafers, European chafer, and oriental beetle. The life history patterns for these species are very similar, although the peak emergence period for adults varies somewhat and under drought conditions some species will delay adult emergence until rains or irrigation moisten the soil profile. The Japanese beetle life cycle is typical of all the key species with annual cycles.
IDENTIFICATION AND BIOLOGY
The adult male beetle is 3/8" long; the female is slightly larger. Roughly oval in outline, the head and prothorax of Japanese beetles are greenish bronze. The wing covers are brownish bronze with green along the sides and center. Japanese beetles have twelve white tufts of hair are present along the sides of the abdomen and at the tips of the wing cover, and plate-like antennae. The legs are long, with heavy claws. The round eggs become oval after absorption of soil moisture, measuring less than 1/16" across. Larvae molt twice; a third instar grub can be up to 1" long. The head is brown, with large, brown-black mandibles.
The Japanese beetle is an Asian native that was first reported in the United States at Riverton, New Jersey, in 1916. It is common in all states east of the Mississippi River except Florida, Mississippi, and Wisconsin. It has also been found in Missouri, Minnesota, and California. Because of the ease of shipping grubs with nursery stock and soil, this species could potentially be found anywhere in the United States, including Hawaii and Puerto Rico. Adults are highly mobile and frequently hitch rides in airplanes and cars. National Park Service lands are at particularly high risk for infestation because of the unrestricted public access.
Adult Japanese beetles feed on more than 300 species of plants including many trees, ornamental shrubs and vines, fruits, flowers, vegetables, and weeds. Adults feed on foliage and fruit, while larvae feed on roots, especially those of grasses, vegetables, and nursery plants. Females prefer to lay eggs in warm, moist soil where turfgrass is exposed to full sunlight.
MONITORING AND THRESHOLDS FOR JAPANESE BEETLES
Larvae feed on grass roots and may move up into the thatch layer after consuming the total root system. In Kentucky bluegrass, populations of 6-8 grubs per ft2 may kill turf during August-October when it is drought stressed, while under the good growing conditions in spring counts of 10-15 per ft2 may cause no damage symptoms. Clump grasses such as tall fescue tolerate higher summer populations but in mixed tall fescue/bluegrass sod, grubs will selectively kill out the bluegrass component.
This root feeding injury gives the turf a spongy feeling when walked upon; after heavy feeding the roots are severed and the sod easily rolled back to observe the grubs. Without irrigation the turf will turn brown, die, and usually not recover. Some improved varieties of Kentucky bluegrass with extensive underground stem systems have better recovery prospects.
Generally, treatments are recommended when grub populations exceed 6-8 per ft2. However, moles and skunks may also destroy turf; because of these small mammals, treatment thresholds can range as low as 4-5 grubs per ft2. In this situation the grubs do not kill the turf; the animals destroy the sod when they dig for the grubs. Cultural conditions such as turf type, amount of irrigation, or time of year may also affect treatment thresholds. If bluegrass turf areas are frequently irrigated during the July-August stress periods, populations as high as 20-25 grubs per ft2 may not produce damage until the irrigation stops. Kentucky bluegrass, perennial rye, and fine fescue grasses are the most sensitive to grub feeding damage. Tall fescue and warm-season species such as zoysia and bermuda can tolerate moderate to heavy populations during the hot dry conditions that kill Kentucky bluegrass lawns. Mixed populations with the masked chafers and other grub species are common throughout the species range.
NON-CHEMICAL CONTROL OF JAPANESE BEETLES
Biological control options include milky disease (Bacillus popilliae), new B.t. strains, parasitic wasps and flies, and parasitic nematodes.
Milky disease provides the first option in the mid-Atlantic states for low-to- moderate maintenance turf situations. This bacterial agent is long- living, species- specific, self-perpetuating, easily-applied, and best adopted to the mid-Atlantic region. Success in New York and New England areas has been limited due to the average cooler soil temperatures and shorter grub season.
This bacterial disease suppresses only the Japanese beetle grub and requires the presence of moderate grub populations in order to increase the soil spore counts and spread the disease to untreated areas. Spores can remain viable for 20-30 years once established in a lawn. However, at the economical rates of application recommended by the manufacturer, effective control may require a two-to-four year establishment period. The granular formulations have not been proven effective to date. The spore dust product is recommended for newly-established turf areas. Areas with ten or more years of turf coverage may already have naturally infected soils. Remember that this disease works most efficiently when grub populations are moderate to high. This situation usually occurs in new housing developments. Some occasional damage can be expected regardless of the spore levels in the soil and age of the turf.
Milky disease is not compatible with insecticides because they kill the grub population that is required to increase and maintain the soil spore counts. Fortunately the spores will remain viable after an insecticide treatment and continue to increase in later years when the grub populations return.
Natural Microbial Control
Japanese beetle grubs are infected by many species of bacteria, fungi, protozoans, and nematodes. Few of these have commercial possibilities but together they constitute one of the major grub population regulators in established turf pastures and meadows. In many older communities problems rarely occur, particularly where turf has been established for eight to ten years or more. The highest risk of grub damage occurs in new lawns two to five years of age or newly-disturbed sites reseeded to turfgrass. New turf areas are often developed from farm fields or wood lots that lack a grub pathogen complex. Pathogens have not developed at these sites because the Japanese beetle and other important grub species do not occur naturally in these habitats. Once grub populations become established after several years, key pathogens and other biological agents also become established and thus help maintain low grub populations.
In the past, B.t. products did not suppress grubs but recent research reveals that both newly discovered and bioengineered strains can provide this missing capability. These new strains show efficacy against the Japanese beetle and masked chafers. Presently the research appears very promising, but commercial labeling is not expected before 1995. At that time, new labeling for B.t. mixtures that control grubs, armyworms, cutworms, and sod webworms should be competitive with insecticides and parasitic nematodes.
Wasp and Fly Parasites
The most effective wasp parasites are the Tiphia wasps. Introduced from Japan, Tiphia popilliavora, and Korea, T. vernalis, these species attack the grub stage in thatch or soil. Historically established throughout the mid-Atlantic region, populations of both species are now low with only scattered pockets of high rates of parasitism. These two species are most effective in areas that have had high populations of grubs (10-30 square foot) over long periods of time. They do not appear to be effective at low population densities which are typical of 90% of our turf areas today. However, they should be introduced into newly-infested areas around the country.
When the adult wasps are abundant, people mistakenly view these low-flying insects as another type of honeybee or yellowjacket, ready to attack and sting. In reality, they are not aggressive and rarely sting even if handled. People throughout Japan accept these wasps without any fear of being attacked.
The only major adult Japanese beetle parasite is a fly imported from Japan, Istocheta aldrichi, sometimes referred to as the Winsome fly. This species prefers adult female beetles and deposits an egg just behind the head on the prothorax. The egg hatches within 24 hours and the maggot enters the beetle body. The adult beetle eventually is consumed and dies within six days. After the adult falls to the ground or buries itself before death occurs, the parasitic fly larva pupates and remains in the soil until the following year.
This fly parasite is limited in distribution to eastern New York and the New England states. USDA and state entomologists made attempts over the past eight years (1982-1990) to reintroduce this New England fly strain into other states (Ohio, North Carolina, Maryland, Virginia, and Kentucky). This effort will continue for another few years. To date this fly has not been recovered in any of these new release sites. However, there may be areas that have localized, undiscovered natural populations. Because the fly is a poor disperser these areas should be explored and parasites collected and moved to new Japanese beetle infestations.
The newest grub biological control agents are parasitic nematodes. These nematode species are selected for their ability to enter the soil, seek out all species of grubs, and quickly parasitize them. Research to date shows that they must be applied when the soil moisture is relatively high for optimal results. Several experimental applications of nematodes at rates of 1 to 5 billion nematodes/acre confirm that the percentage control has been generally good, with the upper ranges near the levels expected with the best soil insecticides. Under optimal conditions one application per season for grub control should be sufficient.
A commercial product with the nematode Steinernema carpocapsae is marketed under the trade names BioSafe, BioVector, and Exhibit. Recent research trials throughout the northeast United States indicate a wide range of efficacy with this species of nematode. The reason for such poor results appears to be a combination of factors, such as product quality, cool soil temperatures at time of application, and extremes in soil moisture levels. Presently S. carpocapsae is not recommended for grub control in turf because this strain appears to be poorly adapted for soil insect control. New product species with S. glasseri and S. feltae and Heterorhabtis sp. appear to be better adapted to search out grubs and other soil insects.
Fortunately the interaction problems with microhabitat and environmental factors can be resolved with new genetic selections from these new species. To date research continues with several companies testing these better-adapted strains. These selections should reach the market in the mid-to-late 1990s.
Soil moisture levels are very important in assessing damage risks in turf. Japanese beetle eggs must acquire moisture from the soil in order to develop and hatch. Research has shown that soil moisture levels less than 10% are lethal to the eggs and newly-hatched grubs. Irrigated areas are also very attractive to egg-laying females, and they ensure good larval survival. If daily irrigation is maintained during these grub outbreaks, Kentucky bluegrass turf can sustain 20 or more grubs per square foot without showing injury. However, once the water is withdrawn, even briefly, the turf dries out and dies.
Turfgrass species and variety selection can greatly influence the susceptibility to grub damage. Perennial rye, bentgrass, Kentucky bluegrass, and fine fescue species are the most susceptible to severe damage, whereas the warm-season grasses like zoysia and bermuda simply outgrow damage and tolerate higher densities of grubs. Tolerance of tall fescue varieties is intermediate to that of bluegrass and warm-season grasses.
CHEMICAL CONTROL OF JAPANESE BEETLES
Consult your National Park Service regional Integrated Pest Management coordinator for pesticide recommendations for Japanese beetle control in your area.
NORTHERN AND SOUTHERN MASKED CHAFER
IDENTIFICATION AND BIOLOGY
The southern masked chafer (Cyclocephala lurida) and the northern masked chafer (Cyclocephala dorealis) are small, yellow-brown beetles 1/2" long with darkened black to chocolate brown areas (masks) between the eyes. The mask becomes lighter in color toward the mouthparts and helps separate these two species from the numerous other similar-appearing May and June beetles. The grubs can be identified by their unique rastral pattern, which is illustrated in Figure 30 on page 118 of Tashiro (1987). Both species have a life cycle similar to the Japanese beetle, except that the adults fly at night and don't feed. Females prefer the same sites as Japanese beetles for egg-laying. Grubs generally feed in upper 1"-3" of the soil profile but move up into the thatch layer for moisture when turf is moisture-stressed.
A broad overlapping distribution occurs in the mid-Atlantic states. Because the grub feeding damage and life histories are similar, both species are frequently referred to as masked chafer grubs. A grub species shift is occurring in many mid-Atlantic areas where masked chafer grubs overlap with the Japanese beetle; reasons not fully understood, urban neighborhoods that previously hosted 80-100% Japanese beetle populations now host to a predominately masked chafer population. Selective natural control by milky disease and other Japanese beetle specific pathogens may be part of the explanation for the shift, as masked chafers are not affected by the Japanese beetle milky disease.
MONITORING AND THRESHOLDS FOR NORTHERN AND
SOUTHERN MASKED CHAFER
Adult masked chafers do not feed and grub damage is identical to Japanese beetle. Populations of 10-15 grubs per square foot can severely damage turf. The adults of both species can be monitored with blacklight traps. The southern species flies just after sundown and activity stops around 12:00 pm. The northern species starts its flight activity at 2:00 am and continues until sunrise. Both species are highly attracted to irrigated lawns during the dry weather and both flight and egg-laying activities will increase significantly after rainstorms.
Masked chafer grubs also feed on organic matter. This results in higher population thresholds for these species. Potter (1982) indicated damage thresholds were 9-10 grubs per square foot for moisture-stressed turf and 15-20 per square foot for non-stressed irrigated turf. Similar to the Japanese beetle, masked chafers frequently intermix with other annual white grub species.
Unlike the day-flying and feeding Japanese beetle adults that can alert turf managers to possible future grub problems, the masked chafer adults fly at night and cause no feeding damage, so turf managers often have no warning of an outbreak. Masked chafer grub injury is often misdiagnosed as Japanese beetle feeding.
NON-CHEMICAL CONTROL OF
NORTHERN AND SOUTHERN MASKED CHAFER
A new strain of milky disease specific for Cyclocephala species has been discovered and looks promising but commercial production may take several years. The Japanese beetle milky disease will not suppress this pest. The parasitic nematodes used to control Japanese beetles will also suppress masked chafers.
The same moisture conditions and turfgrass varieties that reduce Japanese beetle damage will also affect the masked chafers. The wide use of milky disease to control the Japanese beetle has allowed this species to increase its populations because of the lack of competition from the Japanese beetle.
CHEMICAL CONTROL OF NORTHERN AND SOUTHERN MASKED CHAFER
Consult your regional National Park Service Integrated Pest Management coordinator for information on chemical control of these pests in your area.
IDENTIFICATION AND BIOLOGY
May or June beetle (Phyllophaga spp.) adults are 3/4" - 1 3/8" long, stout, shiny red-brown to blackish-brown. The antennae have three plate-like segments forming a club-like structure at a right angle to the other segments. The head, prothorax, and wing covers usually have no distinguishing markings or grooves. Larvae are white with brown heads, have large jaws, and have an elongated raster featuring two parallel lines of hairs, oriented front to rear on the segment. The rastral pattern is pictured in Figure 30 on page 118 of Tashiro (1987).
These species prefer open woods, meadows, lawns, grasslands, cultivated fields and ornamental plant beds. Grubs feed on organic matter and plant roots. The adults of several species cause defoliation of ornamental and shade trees.
These beetles have a two-to-three year life cycle, depending on the species. Eggs are deposited 1"-8" deep in the soil in late spring. The eggs hatch in about three weeks and young larvae begin feeding on roots and decaying vegetation. In the fall, they migrate down into the soil, where they overwinter. The three-year cycle species resume root feeding in the following spring. After a summer of damaging feeding, they hibernate deep in the soil over their second winter, and then rise to near the surface to feed again until about June. Pupation then occurs in a hollowed cavity in the soil. The new adults emerging from these pupae (in about three weeks) remain in the hollow cavities through the following winter and only emerge the following May or June, when feeding, mating, and egg-laying occur.
Although these insects require two to three years to complete their development from egg to adult, adults are present every year because three different broods produce adults in different years. Brood A (with adults to be seen in 1986, 1989, 1992, and so on) produces the greatest damage. Next in importance is Brood C (adults in 1985, 1988, 1991, etc.). Brood B (adults in 1987, 1990, 1993, etc.) is of least importance, since it consists of the fewest individuals (Davidson and Lyon 1979).
Adults fly and feed during the night but hide in soil or sod by day. Trees with new tender spring growth are most susceptible to adult defoliation. Although named May/June beetles, some species emerge in April.
Larval damage to turf is similar to that caused by Japanese beetle grubs. No thresholds are available in the literature. Limited studies in Maryland show that five to seven grubs per square foot may damage turf under drought stress conditions.
NON-CHEMICAL CONTROL OF MAY/JUNE BEETLES
There have been several reports of Bacillus popilliae infecting May/June beetles but it is considered a rare occurrence and a minor influence. Since these species are native to American soils, many species of nematodes, bacteria, and fungal pathogens have been recovered throughout their range.
Similar to the diverse microbial pathogen fauna, numerous species of parasitic wasps and flies attack the adult, grub, or pupal stages. These natural control agents appear to maintain populations below aesthetic damage levels in most areas.
CHEMICAL CONTROL OF MAY/JUNE BEETLES
Insecticides labeled for Japanese beetle also control these species. Consult your National Park Service regional Integrated Pest Management coordinator for information on pesticide selection and timing in your area.
BLACK TURFGRASS ATAENIUS AND APHODIUS GRASSARIUS
IDENTIFICATION AND BIOLOGY
Black turfgrass ataenius (Ataenius spretulus Haldeman) and the related dung beetle (Aphodius granarius (L)) adults are very similar in appearance. Adult beetles are red- brown, darkening to black with aging. Both are roughly oval in shape, and may be up to 3/8" long. Eggs are round, very small, and laid in clusters of 8-12 in the thatch. Grubs are no longer than the adults and resemble other grubs in color, but can be separated by rastral patterns. See Figure 30 page 118 in Tashiro (1987) for an illustration of the rastral patterns. These species have been reported from every continental state except Nevada and Montana.
Both species prefer the same turfgrass microhabitats and frequently form mixed populations. As members of the dung beetle sub-family, the females are highly attracted to dung, compost, piles of decaying grass clippings, and turf thatch. Pest level populations are primarily restricted to golf courses having a combination of high percentage of annual bluegrass and high levels of organic matter in the soil profile. Under these conditions grubs can damage fairways, tees, and greens.
Although these two species are ubiquitous in lawns, meadows, and woodlands, they rarely attain pest status in these habitats. In all habitats, root feeding may be secondary to organic material consumption. Damage to annual bluegrass, Kentucky bluegrass, bentgrass, and fine fescues has been reported, but 80% of the severe damage occurs in the annual bluegrass turf.
There are one to two generations of black turfgrass ataenius per year, depending on climate. There are two generations each year in Ohio, but only one in states farther north (Niemczyk 1981). Adults overwinter 1"-2" below surface in well-drained soils, or under leaves, pine needles and other debris near wooded areas. They emerge in April, mate, and females burrow into the turf to lay their eggs. During May and June, clusters of 8-12 eggs are laid in the thatch or the top 1/2" of soil. Larvae are present from late May to mid-July in thatch and soil. From late June to mid-July, mature larvae burrow 1"-3" inches into the soil, pupate, and emerge as adults in July and early August. These first generation adults lay eggs in July. The second generation larvae complete development and pupate in late August or September. The new adults emerge and seek final overwintering sites during the fall. The life cycle for the Aphodius species is not well- documented. One or two generations are reported with the first occurring one to two weeks earlier than the black turfgrass ataenius.
MONITORING AND THRESHOLDS FOR BLACK TURFGRASS ATAENIUS
Damage from black turfgrass ataenius is similar to Japanese beetle injury. The turf shows localized dry or wilted spots that coalesce over time into large, brown, dead areas. The roots are severed and the dead turf is easily rolled back to expose the feeding grubs. Turf will not recover from severe damage and losses will continue under irrigation.
Peak populations in Maryland golf course fairways range from 150-300 per ft2. An infestation of 30-40 grubs per ft2 will kill annual bluegrass and bentgrass. Kentucky bluegrass and tall fescues are tolerant of similar populations.
NON-CHEMICAL CONTROL OF BLACK TURFGRASS ATAENIUS
Replacement with other more tolerant grass species such as perennial rye, Kentucky bluegrass, zoysia, bermuda, or tall fescue is highly recommended. Bentgrass greens still remain susceptible but the attractiveness to the female is greatly diminished with the elimination of annual bluegrass from the golf course. Elimination of grass clippings piles is also advisable.
A naturally occurring milky disease similar to the Japanese beetle milky disease has become established in most areas east of the Mississippi River. Mortality in the range of 30%-90% has been maintained for seven to ten years on many courses that were devastated in the late 1970's and early 1980's. This milky disease is not produced commercially but spreads by natural agents, mostly birds.
CHEMICAL CONTROL OF BLACK TURFGRASS ATAENIUS
The preference of these insects for high levels of soil organic matter poses a problem for chemical control of these insects because pesticides tend to bind to the thatch and fail to thoroughly penetrate the soil profile. The accumulation of a thick thatch layer also repels irrigation water during the summer drought periods. These combined conditions of thick thatch and high levels of organic matter make grub control extremely difficult with the best insecticide regardless of irrigation levels. Under these extreme circumstances many resource managers prefer to control the adults in the spring before they lay eggs in the thatch. The females entering the thatch to lay eggs are quickly controlled by the insecticide.
To determine when adults will begin laying eggs, visually inspect golf greens for adult beetles. The egg-laying period for the first annual generation corresponds to the full-bloom periods of Vanhoutte spirea and horse chestnut, and the first-bloom periods of the black locust. Second generation egg-laying coincides with the blooming of the rose- of-Sharon (Hibiscus syriacus). Observation of these indicators may be used as a basis for applying controls, but monitoring adults with a blacklight trap is a more accurate method.
Use of herbicides to eliminate Poa annua is also an essential component of a control program for these beetles.
GREEN JUNE BEETLE
IDENTIFICATION AND BIOLOGY
The green June beetle (Cotinus nitida) adult is usually 3/4"-1" long, and 1/2" wide. The top side is forest green, with or without lengthwise tan stripes on the wings. The underside is a metallic bright green or gold, bearing legs with stout spines to aid in digging. In the mid-Atlantic region the names "June bug" and "June beetle" are commonly used for this insect, while they are called "fig eater" in the southern part of their range. They should not be confused the familiar brown May or June beetles that are seen flying to lights on summer nights. The green June beetle adult flies only during the day.
The larvae are white grubs often called "richworms" because they prefer high levels of organic matter for food. With three growth stages, the beetles develop similarly to the other annual scarab species. Their body lengths reach 1/4", 3/4", and 2" respectively. The larvae have stiff abdominal bristles, short stubby legs, and wide bodies. One unique characteristic of this grub is that it crawls on its back by undulating and utilizing its dorsal bristles to gain traction. Other typical white grubs, like the Japanese beetle grub, are narrower, have longer legs, crawl right side up, and when at rest assume a c-shaped posture. This species is native to the eastern half of the United States and overlaps with Cotinis texana Casey in Texas and the southwestern United States.
The adults generally do not feed but occasionally become pests of fruit. Any thin- skinned fruit such as fig, peach, plum, blackberry, grape, and apricot can be eaten. The principal attraction is probably the moisture and the fermenting sugars of ripening fruit. They occasionally feed on plant sap. In turf situations egg-laying females are attracted to moist sandy soils with high levels of organic matter. Turf areas treated repeatedly with organic fertilizers, composts, or composted sewage sludge become more attractive to the female.
The grub feeds on dead, decaying organic matter as well as plant roots. This species is commonly associated with both agricultural crop and livestock production areas as well as urban landscapes. Field-stored hay bales, manure piles, grass clipping piles, bark mulches, and other sources of plant material that come in contact with moist soil provide prime microhabitats preferred by both the female for egg-laying and the migrating third instar grubs.
The green June beetle completes one generation each year. Adults begin flying in June and may continue sporadically into September. On warm sunny days, adults may swarm over open grassy areas. Their flight behavior and sounds reassembles that of a bumble bee. At night they rest in trees or beneath the thatch.
After emerging, the adult females fly to the lower limbs of trees and shrubs and release a pheromone that attracts large numbers of males. Frequently, males repeatedly fly low and erratically over the turf trying to locate emerging females. After mating, females burrow 2"-8" into the soil to lay about 20 eggs at a time. The spherical eggs are white and almost 1/16" in diameter.
Most eggs hatch in late July and August. The first two grub stages feed at the soil thatch interface. By the end of September, most are third instar larvae and these large grubs tunnel into the thatch layer and construct a deep vertical burrow. The grubs may remain active into November in the mid-Atlantic region. In the more southern states grubs may become active on warm nights throughout the winter. In colder areas they overwinter in burrows 8"-30" deep. The grubs resume feeding once the ground warms in the spring and then pupate in late May or early June. The adults begin emerging about three weeks later.
MONITORING AND THRESHOLDS OF GREEN JUNE BEETLES
The green June beetle grub also differs from other white grubs in their feeding behavior. Damage to turf occurs as a result of their unusual habit of tunneling as well as root feeding. Smaller stage grubs tunnel horizontally in the top 4" of the ground, loosening the soil, eating roots, and thinning the thatch. This activity begins in early to mid-August when the disturbed grass may wilt or die if conditions are dry. Damage is minimal when grub density is low or if the grass receives plenty of moisture. As the grubs grow, tunnels become vertical and deeper with turf damage becoming more severe. Grubs keep tunnels to the surface open by pushing little mounds of loose soil to the surface. The resulting mounds appear similar to earthworm castings. To determine that a mound was made by a green June beetle grub, wipe the mound away and feel for a hole in the ground about as wide as your finger. Earthworm holes rarely exceed the diameter of a pencil. The soil mound will reappear the next day. Fecal pellets about as big as mouse or small rat droppings may also be present on the soil surface near the holes. Fresh mounding activity is especially visible after a heavy rain. The mounds and holes are visible by mid-August, but the damage becomes more pronounced in the following months as the grubs continue to grow. The grubs do feed on some roots, but the major damage to the turf results from the upheaval of the acidic subsoil, dislodging of turfgrass roots from the soil, and subsequent weed problems.
The large green June beetle grubs come to the surface at night to feed or graze on the turf; individuals may migrate long distances (20'-30' per night). Grubs may also be found in the twilight hours and on overcast days. Their trails through the dew can frequently be seen on golf course greens.
Besides the direct damage, these grubs cause some indirect problems. The mounds and holes disfigure turf while the tunneling kills the grass. Drought-stressed turf mowed very short succumbs easily to this damage. As a consequence, spaces open up as the grass dies which enables weeds to establish. The tunneling and excavation of subsoil brings acidic soil to the surface and this changes the microhabitat that favors grass and broadleaf weed species. Turf managers using reel mowers have complained that the loose soil and grit from the mounds accumulates on the machinery and dulls the cutter blades, especially when the dew is still on the grass. Additionally, predators such as small mammals and birds damage turf as they dig for the grubs.
To date no thresholds are available for landscape turf or lawns. Treatments are recommended on perennial ryegrass/bentgrass golf course fairways when grub-counts exceed 5 per ft2. Damage thresholds for Kentucky bluegrass and K31 tall fescue based on field observation are slightly higher at 6-7 grubs per ft 2. The K31 tall fescue variety with its broad leaf blades tends to hide damage better than the thin leaf blade species. Kentucky bluegrass will quickly recover with new growth from the underground stems.
To prevent damage to turf, apply controls to grub stages before many mounds become evident. We recommend an action threshold of five third instar larvae per square foot. Damage cycles historically run for 3-6 years then subside. During these outbreaks, damage may be expected if high populations of grubs were present the previous year and insecticide control was inadequate. An increase in the number of adults over the previous year's observations is also a reason to expect damaging populations of grubs.
NON-CHEMICAL CONTROL OF GREEN JUNE BEETLES
To date there are no effective commercial biological agents available to control this grub. The most common parasite is a type of digger wasp, Scolia dubia Say. This beneficial wasp enters the grub tunnel, stings the grub, then lays an egg on the paralyzed grub. The resulting larva feeds in the grub, eventually killing it. In the mid-Atlantic outbreaks during the 1980s, several golf course superintendents noticed an increasing number of digger wasps flying around the course about the time populations subsided. Unfortunately, even though these wasps help reduce the grub population, many people are afraid of being stung and consider them a nuisance. These wasps are not aggressive and need to be forced to sting a human.
Milky disease products effective against Japanese beetle do not control green June beetle grubs nor do any B.t. products.
Some turfgrasses recover from damage once stress factors are removed. For example, species having stolons and rhizomes may repair the damage once the grub population is controlled. Also, the damage resulting from the grub tunneling is less severe when the turf receives sufficient moisture, fertilizer, and lime. Overseeding in the fall is critical in preventing weed encroachment the following season.
It is helpful to remember that grass cut at a greater height (2 1/2"-3") is less stressed and therefore the damage is less visible. Also, grass species such as K31 tall fescue with the broader leaf blades hide damage better than the fine-bladed grasses such as perennial ryegrass, bentgrass, or fine fescue.
CHEMICAL CONTROL OF GREEN JUNE BEETLES
Insecticides are effective on all grub stages and applications may be warranted anytime between August and November, as long as damaging numbers remain active. Spring applications of chemicals are not generally recommended since the grubs are active only for a few weeks and many may have pupated by the time damage becomes obvious. Once the grubs reach the third instar in August or September, they migrate freely and can easily move from an infested area to an adjacent area. To protect golf course greens, treat the greens, collars, and a few yards beyond the collars. The insecticides normally used to control sod webworms, cutworms, and armyworms on the greens will generally suppress migrating grubs. If fairways are treated, the rough areas should be spot-treated where there are high grub populations. The risk of high grub populations is generally correlated with areas where the adult beetle populations were most concentrated.
Most insecticides labeled for Japanese beetle grubs will effectively control Green June beetle grubs. Even insecticides that do not penetrate the thatch layer can work because Green June beetle grubs come up to the surface and become exposed. To control the early instars before the migration phase, application of insecticides must be followed immediately by irrigation with 1/2" of water, or timed with rainfall. Summer applications of isofenphos have not effectively controlled this species.
A word of caution is appropriate concerning insecticide treatment. After treatment, the grubs come to the surface within 12 hours and die, causing a foul odor as they decay. Turf managers should consider the possibility that these poisoned grubs may be eaten by other animals or domestic pets.
Finally, treated areas should be monitored carefully because migrating grubs may reinfest an area once the insecticide has broken down, making retreatment necessary.
IDENTIFICATION AND BIOLOGY
True armyworm (Pseudaletia unipuncta [Haworth]) adults are buff to sand-colored, with a wing spread of about 1/2". Each forewing has a central white dot, and each hindwing has a dark margin. Fully-grown larvae, the turf-damaging stage, are nearly hairless, smooth, green to brown, have one dark stripe along each side, and a broad dark stripe along the upper surface. The top stripe may have a light, thin, broken line along its center. These stripes run the entire length of the body. The head of the larva is light brown with a green tinge and dark brown mottling.
Fall armyworm (Spodoptera frigiperda [Smith]) adults resemble those of true armyworms in form, but have dark gray forewings mottled with light and dark spots, and grayish-white hindwings. Larvae are gray to yellow-green, and have stripes similar to those of P. unipuncta. Each larva has a prominent, white, inverted Y-shaped marking on the front of the head. Long hairs arise from black tubercles along the body.
The true armyworm occurs throughout the United States east of the Rocky Mountains, as well as in New Mexico, Arizona, and California. The fall armyworm occurs throughout the United States in the warmer months, but is found all year in the southern states. This species overwinters in the Gulf Coast states and Florida and continuously migrates north during the spring and early summer.
The true armyworm attacks grasses, small grains, corn, alfalfa, sugarbeets, clover, and tobacco. Within turf and pastures, true armyworms inhabit the thatch layer. Under extremely dry conditions they will seek harborage inside soil cracks and under ground litter. The fall armyworm attacks grasses, corn, cotton, alfalfa, clover, peanuts, tobacco, and many garden plants. The microhabitats in turf, pastures, and meadows are very similar to those selected by the true armyworm.
The true armyworm passes the winter as a partially-grown larva in the soil or under debris in grassy areas. Activity and growth are continuous except during very cold weather. Larvae which successfully overwinter feed during the following spring. When fully grown, they stop feeding for four days, then pupate for 15-20 days. Adults emerge in May and June. Mating takes place at night, especially during the fifth hour after sunset (Pfadt, 1978); multiple matings usually occur. Females feed for 7-10 days on honeydew, nectar, or decaying fruit before laying eggs. Eggs are laid at night in clusters of 25-134 on grass or grain leaves. A single female may live as an adult for 17 days and produce up to 2000 eggs. Eggs hatch in 6-10 days. Young caterpillars begin feeding on leaves, especially at night or during cloudy weather. They usually hide in the thatch during daylight hours. Six larval instars are passed in 3-4 weeks; the last instar consumes 80% of the foliage eaten during the insect's lifespan. Full-grown larvae pupate in flimsy silk cocoon under litter or in earth cells 2"-3" below the soil surface. Following pupation in August or September, the emerging adults mate and lay eggs. Larvae develop partially before winter. The number of generations produced each year increases as latitude decreases; three to four are produced in the central states, while five or more generations are produced in the south. Outbreaks are most common after cold wet spring weather. In seasons of unusual abundance, larvae may crawl in large groups from one food source to another (hence their common name). Armyworms cannot survive exposure to temperatures above 88oF. The fall armyworm life cycle is similar to that of the true armyworm. Although primarily a pest in the South, fall armyworm adults migrate northward each year and have reached pest status as far north as Minneapolis (Niemczyk 1981). Successful overwintering occurs only in the South.
MONITORING AND THRESHOLDS FOR ARMYWORMS
Defoliation damage is nearly identical to sod webworm injury. The only difference is that it proceeds at a faster rate because of the large size of the caterpillars. Synchronous egg-laying and subsequent population growth also contribute to the increased defoliation rate. Both species may be active throughout the growing season and outbreaks may coincide with sod webworm activity.
True armyworm treatment may be triggered when May larval populations reach one per ft2. K31 and other fescues can suffer severe late-summer damage if fall armyworm larval populations reach one per ft2. Other grasses may be more tolerant.
Methods used to sample sod webworms larvae will also work to detect armyworms. Because these two moth species are important agricultural pests, most states monitor the seasonal flight activity with blacklight traps. Your regional National Park Service Integrated Pest Management coordinator should have more information about monitoring programs in your state. Outbreak predictions for corn and other agricultural crops can also be a strong indicator that problems may occur in landscape turf situations.
NON-CHEMICAL CONTROL OF ARMYWORMS
Both of these species are susceptible to a wide variety of pathogens that occasionally become epizootic during major outbreaks. Several B.t. products will control the true armyworm but the fall armyworm requires special strains that are not presently labeled for turfgrass use.
True armyworm larvae may be effectively controlled by the parasite tachinid fly Winthemia quadripustulata. Other insect parasites include Telenomus minimus (an egg parasite); the braconid wasps Apanteles laeviceps, A. marginiventris, and A. militaris; ground beetles; sphecid wasps; birds; toads; domestic fowl; and small mammals such as skunks.
Parasites of fall armyworm eggs and larvae include the ichneumon wasp Ophion bilineatus; the braconid wasps Chelonus texanus, Meterous laphygmae, and Apanteles spp.; Trichogramma minutum; Euplectrus wasps; and the tachinid flies Winthemia quadripustulata and W. rufopicta. Predators include ground beetles, birds, and many small mammals.
Since armyworm damage is similar to scalping the turf with a lawnmower, watering and fertilizing will quickly stimulate regrowth. Turf varieties with high levels of fungal endophytes are highly resistant to both species.
CHEMICAL CONTROL OF ARMYWORMS
Both species prefer to feed at night, so insecticides should be applied in the evening. Most insecticides labeled for sod webworm control will also control both armyworm species. Consult your National Park Service regional Integrated Pest Management coordinator for information on insecticide selection and timing in your area.
IDENTIFICATION AND BIOLOGY
Most of the key turf pest sod webworm species are moths in the genera Crambus, Pediasia, Parapediasia, and Fissicambus. These moths are small, beige to gray-white, some with distinct color bands with a wingspread of 3/4". The head has a snoutlike projection at the front. Wings are folded and wrapped partly around the body when the moth is at rest. The larvae are caterpillars which may be greenish, brown, beige, white, yellow, or gray, depending on the species. They are 3/4" long when mature and usually have dark, circular spots scattered over the body. They spin threads of silk as they move, webbing leaves and soil particles together, and often form silk tubes in which they live. Consult Tashiro (1987) for additional information on the most common species encountered in turfgrass. The single most important species, Parapediasia teterrella, the bluegrass webworm, is detailed as an example for the typical webworm life history. This native species is very common in areas where Kentucky bluegrass is indigenous in the eastern half of the United States.
All species live in the thatch layer in grasslands, lawns, golf courses, rights-of-way, cultivated pastures, and sod farms. Although Kentucky bluegrass and fine fescue blends appear to be the most seriously affected, most cool season cultivated turfgrass species host one or more species. Evidently, slight variations in microhabitat can play a critical part in delineating damage. In Maryland, it was observed that severe outbreaks (10-30 larvae per ft2) of the larger sod webworm and the bluegrass webworm are restricted to turf areas receiving nearly a full day of sunlight. Areas adjacent to fences, trees, shrubs, or buildings that provide partial shade usually host nondamaging populations. These shaded areas may also be less stressed during the drought periods that exacerbate webworm injury.
Depending on the species, length of growing season, and geographic location, the number of generations per year can vary from one to four (or more). The bluegrass webworm, for example, has two generations per year and overwinters as nearly mature larva within a silk-lined tunnel in the soil or thatch. The larvae feed during the evening and pupate within a cocoon at the end of its silk tube. In Maryland, adults emerge in late May and early June, mate, and lay eggs for several days. A second flight occurs in July and August with the mature larvae overwintering. Adults of all species are active at night. During the daylight hours, they rest in the thatch or on broadleaf plants near the turf. Eggs are nonadhesive and randomly drop into the thatch. Generation times are 4-10 weeks depending on the temperature.
MONITORING AND THRESHOLDS FOR SOD WEBWORMS
The sod webworm complex represents over 20 species in the United States, but the leaf feeding damage and the construction of the silken tunnels appear to be behaviors common to all species. Generally, the high-risk period for damage is from mid-July to the end of September, when many of the cool season grasses go dormant. The presence of one to two larger species caterpillars, or three to four small species in Kentucky bluegrass or fine fescue turf, is sufficient to cause defoliation during late summer. The damage is described as a browning of the turf; in reality the armyworms consume the green foliage during the night and the dead thatch layer appears as browning after heavy feeding. The damage caused is equivalent to a severe scalping of the turf like that caused by dull mower blades. Most bluegrass will partially recover when fertilized and watered to break summer dormancy. Fine fescue and perennial rye frequently die from the complete defoliation.
Larval damage can be expected 10-14 days after observations of heavy adult flight activity. Adults are highly attracted to blacklights, so this method can help indicate areas at risk for damage. High trap counts may not always correspond to high damage levels because of insect predation on webworm eggs and larvae.
Larval populations can be sampled using a visual thatch inspection or an irritant flush. Because the small first and second instar larvae are very difficult to find in the dense thatch, visual inspection tends to underestimate populations. The pyrethrin or soap flush, if too concentrated, may also underestimate by population numbers by killing the larvae immediately and allowing only the mature larvae to exit the thatch.
Excessive bird feeding activity in the turf may also indicate the presence or overabundance of mature larvae.
NON-CHEMICAL CONTROL OF SOD WEBWORM
Webworms support a wide range of native predators and parasites. The major predator of the eggs and young larvae are ants, predator, mites, and big-eyed bugs. Older larvae fall prey to birds, ground beetles, parasitic flies, and wasps. Several pupal parasites are well established in the northeast and together all these agents usually keep webworm populations below aesthetic thresholds. Frequent use of insecticides kill these beneficial species and their populations may require one to two years to recover.
Several naturally-occurring Beauveria fungal and Nosema and Phelohania microsporida diseases have been recovered from field-collected larvae. However, the Yimpact of these and other pathogens is poorly understood and probably greatly underestimated.
To date several commercial B.t. products and various species of parasitic nematodes provide good larval control. Both products are limited, however, because of the restricted labeled uses and the costs for multiple applications required to control multiple webworm generations throughout the summer.
The warm-season turf species such as zoysia and bermuda appear to be resistant to webworm feeding. Tall fescue varieties are intermediate with Kentucky bluegrass, fine fescue, hard fescue, and perennial rye species, varying from highly susceptible to moderately resistant. Unfortunately, the selection for turfgrass insect resistance appears less important and more difficult to obtain in breeding programs than other characteristics. Major success has been accomplished in selecting for drought and disease resistance, Ph and fertility tolerances, green color, turf density, and persistence.
Fortunately a newly-discovered enhanced resistance due to a fungal endophyte offers plant breeders a combination of a high level of insect and drought resistance, plus some limited disease tolerance. Endophytes are fungi or bacteria that live inside a plant but do not cause disease. Instead, they enhance a grass's ability to survive drought, disease, and insect attack. At this time a limited number of varieties of tall fescue, perennial rye, and fine fescue possess high levels of protective endophyte. Varieties with endophyte infection levels of 70% or above are recommended.
The following variety tables are the most recent (1991) information on levels of endophyte:
Table 1. Endophyte Levels for Perennial Ryegrass
% Endophyte Content in Seed*
|Variety||Hi||Mod. Hi||Mod. Lo||Lo|
|4 Del. Dwarf||90|
(zero endophyte in other varieties.)
*Note: This data from Rutgers University was obtained from seed lots
submitted to the National Turfgrass Evaluation Program. Seed lots may
contain lower percentages of seeds with viable endophytes because of
loss of viability during seed storage. (Source: Dr. Richard Hurley.)
Table 2. Endophyte Levels for Fine Fescue
% Endophyte Content in Seed*
|Variety||Hi||Mod. Hi||Mod. Lo||Lo|
(zero endophyte in other varieties.)
*Note: This data from Rutgers University was obtained from seed lots
submitted to the National Turfgrass Evaluation Program. Seed lots may
contain lower percentages of seeds with viable endophytes because of
loss of viability during seed storage. (Source: Dr. Richard Hurley.)
Table 3. Endophyte Levels for Tall Fescue
% Endophyte Content in Seed*
|Variety||Hi||Mod. Hi||Mod. Lo||Lo|
*Note: This data from Rutgers University was obtained from seed lots submitted to the National Turfgrass Evaluation Program. Seed lots may contain lower percentages of seeds with viable endophytes because of loss of viability during seed storage. (Source: Dr. Richard Hurley.)
Endophyte-infected grasses control insects in two ways; they repel the insects from feeding and poison them if they do feed. Research at the University of Maryland indicates that the first and fourth instar larvae are highly sensitive but the older larvae are slow to respond to the endophyte toxins. The young larvae die rapidly, one to six days after feeding, whereas older larvae stop feeding and die after five to six days.
Unfortunately no endophytes have been discovered in Kentucky bluegrass, but susceptible varieties with strong rhizome systems are more likely to recover than susceptible clump types. Irrigation and fertilizer applications in the fall will break the bluegrass dormancy and stimulate regrowth. However, complete recovery may require two years and the weakened turf may become more susceptible to summer diseases.CHEMICAL CONTROL OF SOD WEBWORMS
All species of webworms are easily controlled with any of the presently registered insecticides. Control is usually accomplished within 12-24 hours after treatment. Consult your National Park Service regional Integrated Pest Management coordinator for more information on use of pesticides in your area.
BLUEGRASS BILLBUG AND HUNTING BILLBUG
IDENTIFICATION AND BIOLOGY
Eight important species of billbugs attack turfgrass. Adults are gray, black, or brown, usually 1/4"-1/2" in length depending on species. These ground colors are often obscured by soil that adheres to pits, punctures, and grooves on the cuticle. Once cleaned, the surface sculptures on the pronotum and wing covers can be used to separate the species. Billbugs are weevils with a unique characteristic snout. These eight billbug species all have the antennae attached at the base of the snout nearest the eyes. The other major grass-feeding weevils have the antennae attached near the tip of the snout.
The two most common species are the bluegrass billbug, Spenophous parvulus, and the hunting billbug, Spenophous venatus. The Sphenophous larva is white and legless with a brown head capsule. The larvae of the various species are nearly identical and almost impossible to identify. Eggs are sausage-shaped, clear to creamy white. The female inserts these eggs individually into the stem or leaf sheath at the base of the plant.
The drawings and key by Shetlar (1982) should help identify the adults. Specimens should be washed in order to clearly see the diagnostic picture patterns; billbug adults are frequently encrusted with mud. They occur throughout the United States.
The bluegrass billbug is a potential key pest wherever Kentucky bluegrass is grown. This species also attacks perennial ryegrass, fescues, and timothy. The hunting billbug is most serious in zoysiagrass and bermudagrass, although it will feed on other species as well.
Turf with accumulated thatch offers the adult good overwintering harborage and protection from predators. In home landscapes, accumulations of leaves, pine needles, and bark mulches adjacent to turfgrass also provide good protection. Landscape sites that conserve heat during the early spring, such as sidewalk, driveway, asphalt pathway, and concrete or brick walls, encourage females to congregate and deposit higher numbers of eggs in the adjacent turf. Other turf sites in full sunlight are preferred over shaded areas for the same reasons.
Both species have identical one-year life cycles. The adult overwinters, feeds and disperses for a short period, and then begins egg-laying in May and early June in the mid- Atlantic states and Ohio. The adult female chews a small hole in the grass stem or leaf sheath and deposits an egg.
The first instar larva stage feeds inside and hollows the stem, resulting in an accumulation of a light tan powder or fine sawdust-like material inside the stem. The same material is evident in the crown area where the growing larva exits into the soil. The presence of this sawdust-like material helps separate billbug damage from disease injury. The older larvae feeds on roots at the thatch-soil interface.
A partial overwintering second generation will occur in the southern states. In warmer climates older larvae can be found in soil throughout the year. This results from a prolonged egg-laying period in the spring and late summer.
Pupation occurs in mid-July to early August and with the adult emerging between August to September to disperse for winter. Adult populations typically peak in April to late May and again in September to October. Peak larval damage is late June to July.
MONITORING AND THRESHOLDS FOR BILLBUGS
Both species of billbugs damage turfgrass in two ways. The early damage occurs in late June into mid-July. At this time the larva tunnels into the stem and crown causing the stems to brown and die. A good diagnostic sign of this kind of billbug injury is the compacted frass found inside the dead stems. The second type of damage occurs when older larvae feed on roots. These larvae are often intermixed with white grub larvae in the soil.
The collection of six to eight adults in a five-minute search constitutes a moderate infestation. These observations are made on sidewalks, driveways, and patio areas around buildings. Adult billbugs rarely fly, usually walking from lawn to lawn. This sampling method is limited because of the daily variation in adult activity caused by differences in weather, site microclimate, sampling time during the day, and landscape topography. Not all billbugs are active at one time and most are inactive on cool, rainy days. Monitoring done under these conditions will result in less accurate population estimates.
A preferable sampling method is the use of pitfall traps. This method continuously samples populations throughout the adult activity period from early April to late May when egg-laying begins, providing a more accurate population estimate. When trap counts range from two to five adults per day, moderate, spotty turf injury can be expected in two to three weeks. Severe losses can occur when adult counts exceed seven to ten per day over several days of sampling.
Ideally, pitfall traps should be used in combination with degree-day heat unit models and visual scouting. The degree-day models help predict insect activity based on temperature, and serve as a better estimate of peak activity periods during years with abnormal growing seasons.
NON-CHEMICAL CONTROL OF BILLBUGS
Naturally-occurring fungal diseases frequently kill adults during cool, prolonged, rainy periods during the spring and late fall. No fungal agents are registered in the United States. This may change within three to four years as overseas products are tested and labeled for the United States market.
Several commercial strains of entomophathogenic nematodes look promising for billbug control. Steinernema glasseri, S. feltae, and Heterorhabtis spp. nematodes and other experimental strains are all effective, but no commercial products are available to date. S. caropocapsae species are not recommended for billbug control.
Watering and fertilizing to stimulate regrowth of Kentucky bluegrass is an important technique for recovery from billbug injury. Varieties of grasses with extensive rhizome and underground stem systems are better able to quickly recover from billbug damage. Tall fescue and perennial rye grasses appear to better tolerate billbug damage, but once severely damaged they may not recover. Avoid using Kentucky bluegrass cultivars in problem situations that historically host high billbug populations. Some resistant varieties are available but these may have limited geographic usefulness because of other agronomic factors. This limitation may be partially overcome if fungal endophytes can be bred into these susceptible varieties to make them more widely adaptable.
Endophyte-infested tall fescue and perennial ryegrasses are excellent sources of resistance and highly recommended for use in high-risk billbug areas.
CHEMICAL CONTROL OF BILLBUGS
An adult control program offers the best option when billbugs become habitual problems. Two behavior characteristics support this choice. Since the adult female rarely flies, migration into uninfested turf areas each spring is slow. Once established, they require a pre-oviposition period of two to three weeks before egg-laying. Thus an April to mid-May application of insecticide will kill the adult females before they lay eggs. Since there is only one generation per year, reinfestations may not occur again for two to three years after treatment because of the limited migration mentioned above. Billbug grub control is generally less satisfactory than the adult treatments.
IDENTIFICATION AND BIOLOGY
Four species of mole crickets are commonly associated with turfgrass and pastures in eastern half of the United States. Two species, the southern mole cricket (Scapteriscus acletus) and the tawny mole cricket (S. vicinus), are major turf pests in the southeastern United States. The shortwinged mole cricket (S. abbreviatus ) and the northern mole cricket (Neocurtilla hexadectyla) are less important as pests. Adults are 1/2"-2" long, and may be grayish-brown to brown in color, with enlarged heads, beadlike eyes, short antennae, and robust, spadelike front legs with large spikes used for digging. Forewings are usually half the body length, while the hindwings may extend beyond the tip of the abdomen when folded except in the short-winged species. Mole cricket nymphs resemble adults but are smaller and wingless. Eggs are deposited in clusters in the soil. The northern mole cricket has four claws on the front pair of legs, while the other species have only two.
The shortwinged, southern, and tawny mole crickets occur in the south- Atlantic and Gulf Coast regions from Virginia to Texas. The shortwinged species is restricted to coastal Florida and Georgia. The southern mole cricket is the most widespread of the three. The northern species is found throughout the eastern half of the United States.
The southern and tawny mole crickets have very similar life cycles, habits, and destructive behavior. Nymphs and adults migrate deep into the soil during cool weather and pass the winter in the soil. In spring and early summer, females construct cells in the soil in which they lay about 35 eggs are laid in each cell. These hatch in 10-40 days, depending on ambient temperatures. Nymphs grow rapidly, most becoming adults before fall. Those emerging from eggs laid late in the season will become adults in the spring of the following year.
Nymphs and adults of both the southern and tawny species feed on various warm- season grasses. Bermuda and bahia grass appear to be the major hosts. Mole crickets also feed on garden vegetables, tobacco, peanuts, and strawberries. Underground stems, roots, tubers, and fruits touching the ground may also be damaged.
Mole crickets are rarely found in heavy soils, preferring sandy to sandy loam soils. Regardless of texture, moderate to high soil moisture is a prerequisite in maintaining the open tunnel structures. Nightly tunneling ranges from 5'-20'. Both nymphs and adults hide in this tunnel system by day and emerge at night to feed on plants, roots, organic matter, and other arthropods. They can be cannibalistic, particularly the southern species.
MONITORING AND THRESHOLDS FOR MOLE CRICKETS
Immatures and adults burrow in loose soil, feed on grass roots, and cause the turf to dry out. Damage is usually localized in irregular areas and can be severe in newly- planted turf. Infested areas may feel soft underfoot due to the tunnels under the thatch. Suspect turf can be visually inspected for the presence of entrance holes (1/2"-1" in diameter) in the soil or thatch layer. A quantitative estimate of mole cricket populations is obtained using the soap flush technique. A solution of 1-2 ounces of liquid dishwashing soap in 2 gallons of water is sprinkled over a marked 4 ft2 area of turf. The soap irritates the insects, driving them to the surface. All mole crickets coming to the surface in the three-minute period following treatment are counted and the total is divided by four to convert to number per square foot (Short et al. 1982). Short et al. (1982) determined the economic threshold for this pest at 2 per 0.1 m 2 for bahia grass lawns in Orlando, Florida.
Other thresholds are based on a 4 ft
Another source of aesthetic damage is the mound of soil that accumulates at the tunnel entrance. These small mounds produced by the tunneling nymphs and adults will cause problems on golf course greens and tees, regardless of population levels. Their presence also interferes with play and mowing activities.
NON-CHEMICAL CONTROL OF MOLE CRICKETS
Several researchers report that the green disease (metch), which is caused by the fungi Metarrhizium anisopliae, and the red disease, which is caused by the fungi Sorosporella uvella (Kass), will infect mole crickets. However these naturally-occurring fungal diseases are not consistent from year to year. Several commercial products with the Metarrhizium fungi are available outside the United States, but similar products are expected to be registered here by 1994.
The most promising biological agent to date is the parasitic nematode Steinernema scapterisa. Preliminary research by Parkman and Frank at the University of Florida demonstrated that sound traps using two Mans-type emitters, each set for a single species, can be used to attract and expose mole crickets to this nematode. Early studies also determined that this nematode could be released once and persist for several years in pastures. Commercial products with this unique mole cricket nematode should be available after 1993.
Natural occurring parasitism and predation is limited, but fire ants, ground beetles, spiders, and mole crickets themselves do help regulate populations. Two imported parasites have been released in Florida and show some promise. The sphecid wasp Larra bicolor (americana), which is found in southern Florida, seeks out the mole cricket in the tunnel, paralyzes it, and lays an egg on the thorax. In about two weeks the developing wasp larvae kills its host. The other imported parasite is a tachinid fly called Ormia depleta. This fly is attracted to the sound produced by the mole crickets. After finding the mole cricket, the fly lays an egg on the host; the developing maggot stage then kills the host.
The combination of fertilizing, irrigating, and rolling the turf in the spring will lessen the spring tunneling damage. The rolling helps prevent the root system from drying out in light sandy soils.
CHEMICAL CONTROL OF MOLE CRICKETS
Because mole cricket migratory flights occur twice a year and both adults and nymph tunnel extensively, the risk of continuous reinfestations is high. Therefore, two insecticide treatments may be required. Contact insecticides are most effective against the newly-hatched crickets. With late-season outbreaks or with early spring tunneling, short-residual insecticides are recommended. Insecticide baits also work well against the nymphs, but are relatively ineffective against adults in fall. Regardless of the insecticide strategy selected, adults are very difficult to control. Consult your National Park Service regional Integrated Pest Management coordinator for more information on chemical control of this pest in your area.
IDENTIFICATION AND BIOLOGY
Two species of chinch bugs are of primary concern in turf; the southern chinch bug (Blissus insularis), a pest of warm-season turfgrasses, and the hairy chinch bug (Blissus leucopterus hirtus), a pest of cool-adapted turfgrasses. Adults are black, about 1/5" long, with white wings folded over the back. Each wing is marked with a dark triangle on the outer margin. As many as 80% of these individuals may have short wings (about 1/2 the length of the body), while the wings of others extend to the tip of the abdomen. The legs and the bases of the antennae are red. Juveniles (nymphs) resemble adults, but are wingless; the youngest nymphs are bright red with a single white band across the middle of the body, but darken as they mature. Eggs are elongate and about 1/15" long and usually inserted into the leaf sheath or crown area.
Chinch bugs occur throughout the United States. The southern chinch bug is a pest in the Gulf states, Georgia, South Carolina, and North Carolina. The hairy chinch bug is a pest of the more northern states.
Chinch bugs overwinter as adults, hiding in tufts of bunching grasses, under litter or leaves at woodland borders, under hedges, in fence rows, or in crop stubble. Winter inactivity may be broken by abnormally warm weather. Generally, migration from winter sites begins after one or two sunny days with temperatures of 70 oF or more. Females lay eggs in leaf sheaths, in the crown-area roots, or on the soil near host plants. Fifteen to twenty eggs per day are deposited in two to three weeks. Eggs hatch in one to two weeks and nymphs begin sucking juices from host plants. The bugs pass through five instars in 30-90 days before reaching adulthood. The eggs produced by this generation of females become the second generation of adults in late summer and early fall. From August to October, these adults gradually migrate to their overwintering sites. In the south and southwest, three or more generations may be produced before hibernation.
MONITORING AND THRESHOLDS FOR CHINCH BUGS
The chinch bug prefers the following grasses listed in order of importance:
Hairy chinch bugSouthern chinch bug
Chinch bugs damage grass plants by inserting their hollow beaks into the stems, sucking the plant juices, and injecting chemicals into the plant which clog the vascular system. The area around the feeding puncture usually turns yellow. Damage appears as patches of dead or gradually yellowing grass, especially where heat is radiated into the grass from sidewalks or roadways. Once the grass turns brown, the turf will not recover.
Reseeding or renovation is usually necessary after moderate damage. Usually 15-20 chinch bugs per square foot will require treatment. Chinch bugs prefer warm, sunny, dry locations. Adults rarely fly in the mid-Atlantic region. However, in Canada, where the short-winged form is limited in numbers, adults frequently fly from lawn to lawn. The best way to monitor chinch bug activity is by flotation sampling, which is described in the section on monitoring at the beginning of this module.
NON-CHEMICAL CONTROL OF CHINCH BUGS
Naturally occurring fungal diseases such as Beauveria globcelifera regularly control chinch bugs during cool, wet weather. Another regulating biological agent is the big-eyed bug, which can destroy entire populations; unfortunately, chinch bugs frequently cause serious damage before big-eyed bug populations peak. The wasp Eumicrosoma beneficum may parasitize up to half of the chinch bug eggs in favorable locations.
Commercial parasitic nematode products which contain the nematode Steinernema carpocapsae are effective against chinch bugs.
Resistant Turf Varieties
Several highly resistant varieties are now marketed, particularly for the southern species. The cooperative extension service can provide variety recommendations for your geographic area. Recently discovered fungal endophytes provide enhanced resistance. Chinch bugs both avoid turf plants with endophyte or die quickly after feeding. The naturally- resistant St. Augustine grasses and the endophyte-enhanced varieties offer the best long-term, environmentally-sound control choice available at this time.
Research at the University of Maryland has documented an immediate, rapid decline in mortality in young nymphs feeding on the endophyte-infested turf varieties. A similar but slower mortality rate was observed among the adult insects.
CHEMICAL CONTROL OF CHINCH BUGS
Resource managers usually control populations after major damage has occurred. To avoid this problem, areas with habitual problems should receive an insecticide application in April to mid-May that will control the overwintering females and subsequent generations during the summer. Reinfestation may occur from adjacent areas, but this process is slow and may require an additional year. This treatment must be made before egg-laying occurs in early to mid-May in the mid-Atlantic states. Consult your National Park Service regional Integrated Pest Management coordinator for more information on chemical controls in your area.
1. Converse, J. 1982. Scott's Guide to the Identification of Turfgrass Diseases and Insects. OM Scott and Sons, Co., Marysville, OH.
2. Daley, R.C. (ed.) 1975. Guide to Turfgrass Pests. National Pest Control Association, Vienna, VA.
3. Davidson, R.H. and W.F. Lyon. 1979. Insect Pests of Farm, Garden and Orchard. John Wiley and Sons, NY.
4. Hellman, J.L., J.A. Davidson and J. Holmes. 1982. Urban ornamental and turfgrass integrated pest management in Maryland. In H.D. Niemcyk and B.G. Joyner (eds.). Advances in Turfgrass Entomology. Hammer Graphics, Inc., OH, pp. 31-39.
5. Niemczyk, H.D. 1981. Destructive Turf Insects. Gary Printing Company, Fostoria, OH.
6. Pfadt, R.E. (ed.). 1978. Fundamentals of Applied Entomology, 3rd edition. Macmillan Publishing Co., Inc., NY.
7. Reinert, J.A. 1982a. A review of host resistance in turfgrasses to insects and acarines with emphasis on the southern chinch bug. In H.D. Niemczyk and B.G. Joyner (eds.). Advances in Turfgrass Entomology. Hammer Graphics, Inc., OH, pp 3-12.
8. Reinert, J.A. 1982b. Evaluation of cool-season turfgrasses for resistance to the hairy chinch bug. Pages 13-18 In H.D. Niemczyk and B.G. Joyner (eds.). Advances in Turfgrass Entomology. Hammer Graphics, Inc., OH.
9. Shetlar, D. 1982. Turfgrass Insect and Mite Identification Manual. Pennsylvania Turfgrass Council, University Park, PA.
10. Short, D.E., J.A. Reinert and R.A. Atilano. 1982. Integrated pest management for urban turfgrass culture - Florida. In H.D. Niemcyk and B.G. Joyner (eds.) Advances in Turfgrass Entomology. Hammer Graphics, Inc., OH, pp 25-30.
11. Tashiro, H. 1987. Turfgrass Insects of the United States and Canada. Cornell University Press, Ithaca, NY.