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Integrated Pest Management Manual

Exotic weeds II

Exotic Weeds 2
This module is intended to serve as a source of basic information needed to implement an integrated pest management program for tree of heaven, Japanese honeysuckle, mimosa tree, siris tree, giant sensitive plant, and sensitive plant. Any pest management plan or activity must be formulated within the framework of the management zones where it will be implemented. Full consideration must be given to threatened and endangered species, natural and cultural resources, human health and safety, and the legal mandates of the individual parks. Recommendations in this module must be evaluated and applied in relation to these broader considerations.



This module discusses the biology and management of six woody weeds that are either trees, shrubs, or vines and are distributed throughout many regions of the United States. They are pests because they are invasive and can displace native vegetation and because they create floristic inaccuracies in historical landscapes due to their foreign origin. One is an alternate host to an important nematode pest of agronomic crops.

In some cases exotic vegetation is allowed to remain because it is historically accurate and contributes to the character of a cultural landscape. For example, some introduced species were brought to an area during a certain time period or by a particular group and thus provide important information about the history of a site. Although historically correct, these species become an immense problem if they are not kept from spreading. Many historic sites have fallen into disrepair, allowing introduced plant species to spread into natural zones and force out native vegetation. Natural resource managers, cultural resource managers, and maintenance personnel must work together to establish priorities for the preservation of historic landscapes that consider protection of both the cultural and natural resource.


IDENTIFICATION AND BIOLOGY OF TREE OF HEAVEN, JAPANESE
HONEYSUCKLE, MIMOSA TREE, SIRIS TREE, GIANT SENSITIVE PLANT,
AND SENSITIVE PLANT


Tree of Heaven

Tree of Heaven (Ailanthus altissima [Miller])is in the family Simaroubaceae. It was introduced into the United States from Asia (China) as a host tree for the Cynthia moth, Samia cynthia (Drury), which was introduced for silk production. It was brought to the eastern United States as nursery stock because of its ability to grow quickly under adverse conditions. Chinese miners also brought the seeds with them to California because of their medicinal and cultural importance. Distribution in the United States is from Massachusetts to Iowa and Kansas and south to southern Texas and Florida. Tree of heaven has established to a lesser extent in the western United States from southern Rockies to the Pacific Coast states. It is a tall (to 60'), deciduous, polygamous tree and often colonizes by root sprouts. Stump sprouts can grow 6'-12' in length in a single summer. Flowers are present in late May through early June in 12" long terminal panicles. A large cluster of pink fruits develops from July to October. The flowers and vegetative parts, if bruised, are ill scented, almost nauseating, on hot days.

Tree of Heaven is intolerant of deep shade and occurs most commonly along fence rows, roadsides, and waste areas. It is tolerant of urban conditions, including compacted, poor soils, and polluted air, and is common in dusty, smoggy areas such as inner cities where most other trees fail. It is often used as an ornamental in urban areas. It spreads rapidly in disturbed areas and can quickly take over forest openings created by gypsy moth damage or fire. It can pose a serious threat to natural areas. It has been found growing up to two air miles from the nearest seed source.

Japanese Honeysuckle

Japanese honeysuckle (Lonicera japonica [Thunberg]) is a high climbing or trailing vine in the family Caprifoliaceae. It was introduced into the United States from Asia. Distribution in the United States is from the central Atlantic states to Missouri and Kansas, south to Florida and Texas. Japanese honeysuckle stems are glabrous to densely pubescent. Leaves are 3/4"-2 1/2" long, evergreen, oval in shape, with a rounded base. In spring the leaves of new shoots are often lobed. The flowers are very fragrant and occur in pairs. They are white or pink when they first appear and fade to yellow with age.

This vine, originally planted as an ornamental and to stabilize road banks, has invaded woodlands, fence rows, and fields, outcompeting and killing native wild flowers, shrubs, and tree seedlings. It is common to abundant at low altitudes, but can spread into uplands. It grows best in full and partial sun but t olerates partial shade. This species is considered a major pest due to its ability to outcompete and shade out native vegetation.

Mimosa Tree, Powder-puff Tree, Silktree, Mimosa

Mimosa tree (Albizia julibrissin [Durazzini]) as introduced into the United States as an ornamental from Asia and Africa. Distribution in the United States is from the mid-Atlantic states south, and as far west as Indiana. It is a flat-topped, thornless, deciduous tree which reaches 35' in height.

The mimosa tree was introduced as an ornamental but escaped into fields and waste areas. It does not establish in forests, but commonly occurs on forest borders. It can also invade riparian areas and spread downstream. It is often injured by severe winters. Its major negative impact is its improper occurrence in historically accurate landscapes.

Siris Tree, Woman's Tongue

Albizia lebbeck (L.) Benth. (family Leguminosae) was introduced from Egypt into southern Florida about 1900 where it escaped from cultivation. It is probably a native of tropical Asia, but is widely planted throughout the tropics as a shade tree and ornamental. Its range extends to Bermuda and the West Indies, Central America, and south to Brazil. It is a medium-sized deciduous tree 20'-40' high, to 1/2' in diameter or larger, with a spreading crown of thin foliage. The bark is gray, and smooth but becomes rough as the tree ages. The fruits are flat pods, which are broad, straw- colored, 4" to 8" or more in length, and 1" to 1/2" wide. They usually occur in large numbers. Pods remain on the tree for some time after the seeds and leaves have fallen. The sound of the empty pods rattling in the wind gives the tree its common name of woman's tongue.

This species propagates readily from seed and has established in pastures and on hillsides in dry coastal regions. This species is highly tolerant of salt spray but is intolerant of cold temperatures.

Giant Sensitive Plant

The giant sensitive plant (Mimosa invisa [Mart.]) is a native of Brazil. This species is a weed in many tropical and subtropical countries and is found in the United States in Hawaii. An erect, climbing shrub, the giant sensitive plant is biennial or perennial depending on the climate, and often forms dense thickets (Holm et al., 1977). This species possesses a strong root system that often becomes woody at the base. Stems can be up to 6' tall, and are conspicuously angular, with many randomly scattered recurved spines or thorns 1/4"-1/2" in length. The seeds are flat, about 1/4" long, and are adapted for dispersal by animals. Seedlings only a few weeks old may produce viable seeds. Some of these may germinate immediately while others may remain in the soil for several years before germination. See Holm et al. (1977) for illustrations.

Often found in moist waste places, plantations, pastures, and cultivated areas, this plant has become a serious weed in sugar cane plantations. It covers other vegetation with the spiny stems, forming spreading tangled masses or impenetrable thickets up to 6' high.

This species has been designated a noxious weed by the United States Department of Agriculture (Westbrooks 1981). It overruns and outcompetes native vegetation in large areas. It further affects native species by being unpalatable to most grazers and by trapping animals caught in thickets; animals or people may die or become seriously injured if they become ensnared in these thickets. Animals will not browse or step on stems due to the recurved thorns (Holm et al. 1977).

Sensitive plant

The sensitive plant (Mimosa pudica [L]) is a multistemmed, perennial shrub in the legume family. Originally from tropical America, the sensitive plant is widely introduced and is now found throughout the New World tropics. It is considered a troublesome weed in the Caribbean region and South America. In the United States its distribution is limited to Hawaii and Puerto Rico. Its bristled seeds are dispersed by attachment to animals or people. Seeds may remain in the soil for several years before germination; seeds stored under laboratory conditions have shown 2% germination rates after 19 years (Holm et al. 1977). See Holm et al. (1977), Radford et al. (1964), Fernald (1950), Little (1953), Little and Wadsworth (1964), and Gleason (1963) for more detailed descriptions of this species.

Sensitive plant is found in cultivated areas, lawns, and waste places. It grows on a wide variety of soils and has a high tolerance for shade. It is often grown as an annual ornamental for its showy flowers and as a cover crop in some tropic countries for its nitrogen-fixing abilities. It occurs as a common weed in many cultivated crops and in pastures, where its high populations and thorny stems make grazing difficult. Sensitive plant is an alternate host to several species of parasitic flowering plants and of the root-knot nematode Meloidogyne sp., which is a serious pest of many crop plants (Holm et al. 1977).


MONITORING AND THRESHOLDS

Monitoring techniques for the introduced weed species described above consist of periodic visual inspections. All observations and treatments should be recorded.

Care should be taken to monitor small, slowly expanding populations which have not reached pest status. A slight change in environmental conditions, such as drought or fire, could enable populations to grow rapidly (Anonymous 1983). Control efforts should be undertaken whenever any of these species is observed, as they can all spread rapidly and overtake desired vegetation.


NON-CHEMICAL CONTROLS

Tree of Heaven

Cutting. This process involves removal of all above-ground growth. Regeneration of stump sprouts and from underground parts is not prevented.

Japanese Honeysuckle

Cutting. Vines may be chopped just above ground level. Cutting is repeated every two weeks to deplete nutrient reserves in the roots and prevent resumption of photosynthesis. Cutting does not affect roots, which will continue to grow until their energy and nutrient supplies are depleted.

Flaming. By placing a kerosene torch over leaves on the same schedule as cutting, foliage is wilted and nutrient supplies in the roots are depleted. As with cutting, flaming will not affect roots.

Burning. Although few quantitative studies occur in the literature, Barden and Matthews (1980) recommend controlled burning. Two annual burns in an experimental plot reduced honeysuckle crown volume by 80%. Ground cover was reduced by 35%. Fires killed most above-ground vines, but ground cover was maintained by re- sprouting roots. Burning may be combined with previous flaming, which wilts and dries leaves, providing fuel for the burn.

Grubbing. Consists of mechanical removal and destruction of the entire plant, including the root. If all root tissue is removed, no regrowth can occur, and repetition is not necessary. Grubbing is labor intensive and may be locally destructive. Grubbing is most effective from fruiting to winter and early spring when plant reserves are lowest.

Grazing. Controlled grazing by goats may serve to reduce honeysuckle crown and ground cover densities, but as with controlled burning, re-sprouting roots will regenerate unless nutrient reserves are depleted by continuous grazing pressure.

Regardless of the control method used, care must be taken to prevent re- invasion from nearby areas, or by seeds transported by birds or other wildlife. Planting the area with fast-growing native vegetation or grasses may prevent recolonization.

Mimosa Tree

Cutting. See Tree of Heaven.

Siris Tree


Cutting. See Tree of Heaven.

Giant Sensitive Plant

Controlled burning. See Japanese honeysuckle.

Sensitive Plant

Controlled Burning. See Japanese honeysuckle.


BIOLOGICAL CONTROL

Tree of Heaven

The Cynthia moth, Samia cynthia, feeds on this species, but it is rare outside of urban habitats (Pyle 1983).

Japanese Honeysuckle

No natural enemies are reported for this species.

Mimosa Tree

Attacked by mimosa wilt, Fusarium oxyapoeum perniciosum, a fungus. It is also fed upon by the mimosa webworm, Homadaula anisocentra Meyrick, and the root-knot nematode Meliodogyne incognita.

Siris Tree

No natural enemies are reported for this species.

Giant Sensitive Plant

No natural enemies are reported for this species.

Sensitive Plant

No natural enemies are reported for this species.


CHEMICAL CONTROL

Tree of Heaven

Current treatment consists of felling and stump treatment with herbicide. Chemical treatment kills remaining tissue and prevents regrowth of stump sprouts. Trees may be frilled and treated with felling, treated by injection, or treated by hack and squirt. The latter technique involves cutting into the cambium and applying a herbicide into the wound.

Honeysuckle

Mclemore (1981) reports that an acceptable level of control (70%) was reached during a two-year experimental program which used 2 lb/acre of glyphosate in the first year and 6 lb/acre in the second year. Japanese honeysuckle is an evergreen, so it can be treated in the dormant season with less damage to non-target species.

Mimosa Tree

Use the same treatments described in the Tree of Heaven and Honeysuckle sections.

Siris Tree

Everglades National Park has successfully used basal bark sprays of herbicide for management of this plant. It is applied to runoff to the complete circumference of the trunk 12" to 15" above the ground (Anonymous 1983). A carrier and dye are added to the herbicide to ensure good penetration and complete coverage by the herbicide.

Giant Sensitive Plant

See Sensitive Plant section.

Sensitive Plant

Patro and Tosh (1974) recommend postemergence application of 2,4-D as the best chemical control measure for this species.

Consult with your regional integrated pest management coordinator to determine which, if any, pesticide is best suited to your integrated pest management program.


SUMMARY

Tree of Heaven

Felling individual problem trees and treating the cut stumps with approved herbicides to prevent regrowth may be sufficient for control in most situations. Depending on the growth form of the plant, basal-bark treatments or foliar treatments with herbicide may be necessary as well.

Japanese Honeysuckle

Regular cutting (or flaming, where applicable) followed by spot treatments of herbicides or regular controlled burns combined with spot treatments or grazing pressure may control honeysuckle in most situations. Grubbing or other mechanical methods should be sufficient for small infestations.

Mimosa Tree

See Tree of Heaven section.

Siris Tree

See Tree of Heaven section.

Giant Sensitive Plant

Flaming, burning, and postemergence applications of herbicide followed by spot treatments with approved herbicides may be sufficient for control in most situations. Broadcast treatments with approved herbicides may be required to treat large infestations.

Sensitive Plant

See Giant Sensitive Plant section.

REFERENCES

1. Anonymous. 1980. Suggested Guidelines for Weed Control. U.S. Dept. Agriculture, Washington, D.C., Ag. Handbook, No. 565.

2. Anonymous. 1983. Exotic Plant Control Program. Everglades National Park and Fort Jefferson National Monument. U.S. Dept. of the Interior, NPS. (Looseleaf binder).

3. Barden, L.S., and J.F. Matthews. 1980. Change in abundance of honeysuckle (Lonicera japonica) and other ground flora after prescribed burning of a piedmont pine forest. Castanea 45:257-260.

4. Berg, G.L. (ed.). 1980. 1980 Weed Control Manual. Meister Publishing Co., Willoughby, OH.

5. Brown, R.G., and M.L. Brown. 1972. Woody Plants of Maryland. Univ. MD., College Park, MD.

6. Fernald, M.L. 1950. Gray's Manual of Botany. Eighth edition. American Book Co., New York.

7. Gleason, H.A. 1963. The New Britton and Brown Illustrated Flora of the Northeastern United States and Canada. Volume 3. New York Botanic Garden, New York.

8. Holm, L.G., D.L. Plunckett, J.V. Panch, and J.P. Herberger. 1977. The World's Worst Weeds: Distribution and Biology. University Press, Honolulu, Hawaii.

9. Little, E.L. 1953. Checklist of Native and Naturalized Trees of the United States (including Alaska). U.S. Dept. Agriculture; Forest Service, Washington, D.C. Agriculture Handbook No. 41.

10. Little, E.L., and F.H. Wadsworth. 1964. Common Trees of Puerto Rico and the Virgin Islands. U.S. Dept. Agriculture Forest Service, Washington, D.C. Agriculture Handbook No. 249.

11. Mclemore, B.F. 1981. Evaluation of Chemicals for Controlling Japanese Honeysuckle. Proc. South. Weed Sci. Soc. 34:298-210.

12. North, R.C., and E.R. Hart. 1983. Oviposition preference of the mimosa webworm, Homadaula anisocentra (Lepidoptera: Plutellidae). Environ. Entomol. 12(2):546-551.

13. Patro, G.K., and G.C. Tosh. 1974. A note on chemical control of Mimosa pudica. Farm J. (Calcutta) 15(3):11-12.

14. Pyle, R.M. 1983. Urbanization and endangered insect populations. In Frankie, G.W. and C.S. Koehler (eds.) Urban Entomology: Interdisciplinary Perspectives. Praeger Publishers. New York.

15. Radford, A.E., H.E. Ahles, and C.R. Bell. 1964. Manual of the Vascular Flora of the Carolinas. Univ. N. Carolina Press, Chapel Hill, NC.

16. Westbrooks, R.G. 1981. Introduction of foreign noxious plants into the United States. Weeds Today. 12(3):116-117.


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