Fall webworm
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| Fall Webworm | ||||||||||||||
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| Hyphantria cunea Drury, 1773 |
Fall webworm, Hyphantria cunea, is a moth in the family Arctiidae known principally for its larval stage, where it creates the characteristic webbed nests on the tree limbs of a wide variety of hardwoods in the late summer and fall. It is mainly an aesthetic pest and is not believed to harm otherwise healthy trees. It is well-known to commercial tree services and arboriculturists.
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[edit] Range
The moth is native to North America, ranging from Canada to Mexico, and is one of the few insect pests introduced from North America into other continents. Introduced to what was formerly Yugoslavia in the 1940s, it now has occupied probably its entire range in Europe from France to the Caspian Sea in the east. It was also introduced into Japan in 1945, and has adjusted its number of generations per year since its arrival.[1] It spread into Korea and China and now is considered Holarctic in distribution.
[edit] Life cycle
One generation per year emerges in the northern part of North America, with larvae appearing in late summer through early fall. South of an approximate latitude of 40 degrees north there are two or more generations annually, with webs appearing progressively earlier further south.[2]
[edit] Egg
The adult moth lays her eggs on the underside of leaves in 'hair'-covered clusters of a couple of hundred.[3] Eggs hatch in about a week.[4]
 late instar larva |
 Web on willow |
[edit] Larva
The larvae are highly variable in coloration, ranging from a pale yellow, to dark grey, with yellow spots and long and short bristles.[5] There are two cream stripes along the sides. There are two races, one more common in the north, the other in the south, differing in head capsule coloration.[4] Maximum length, 35mm. Webs are progressively enlarged, and much messier looking than those of tent caterpillars (which occur only in spring and have shorter hairs and very little yellow on their bodies). Larvae feed inside the tents until the late instars. Very young larvae feed only on the upper surfaces of leaves. Later, they consume the whole leaf. The larval stage lasts about 4-6 weeks.[4]
[edit] Pupa
The pupal stage overwinters in the bark and leaf litter at the base of the trees. It is dark brown and about 10 mm long. They have thin brown cocoons made of silk with bits of detritus interwoven.[4] This stage overwinters.
[edit] Adult
The adult is mostly white in the north, but in the south it may be marked with black or brown spots on the forewings.[4][3] It is quite 'hairy', and the front legs have bright yellow or orange patches. The underwings will have less marking than the forewings, and the abdomen often has a sprinkling of brown hairs. Wingspan of 35-42 mm.
[edit] Food plants
The fall webworm feeds on just about any type of deciduous tree. Worldwide, it has been recorded from 636 species,[6] and is considered to be among the most polyphagous of insects. In the eastern U.S., pecan, walnut, American elm, hickory, fruit trees, and some maples are preferred hosts; in some areas persimmon and sweetgum are also readily eaten. In the west, alder, willow, cottonwood and fruit trees are commonly used.[3]
[edit] Control
Cutting off and then burning the affected limb works. Application of Bacillus thuringiensis early in spring is also useful. In terms of chemical warfare, Sevin, permethrin, and cyfluthrin can also be used. The female of the various species of the Trichogramma wasp is the natural parasite, laying her own eggs into the eggs of the moth.
Fall webworm is not considered as harmful to orchards as the Eastern tent caterpillar, because it feeds late in the season and only shortly before leaf drop.
[edit] Notes
- ^ Gomi, Takeda (1996). "Changes in life-history traits of Fall Webworm within half a century of introduction into Japan.". Functional Ecology 10:384-389.
- ^ Wagner, DL (2005). Caterpillars of Eastern Forests. Princeton, NJ: Princeton Univ. Press.
- ^ a b c Douce, GK. "The Fall Webworm". Accessed August 21 2006.
- ^ a b c d e Hyche, LL. "Fall webworm: A Guide to Recognition and Habits in Alabama". Accessed August 21 2006.
- ^ Wagner, DL (2005). Caterpillars of Eastern Forests. Princeton, NJ: Princeton Univ. Press.
- ^ Warren, Tadic (1970). The fall webworm, Hyphantria cunea (Drury). Arkansas Agric. Exp.Sta. Bull.
[edit] References
Douce, GK, 2003. The fall webworm. http://www.bugwood.org/factsheets/webworm.html . Accessed Aug 21, 2006.
Gomi, T and M Takeda. 1996. Changes in life-history traits of Fall Webworm within half a century of introduction into Japan. Functional ecology 10:384-389.
Hyche, LL, 1999. Fall webworm: A guide to recognition and habits in Alabama. http://www.ag.auburn.edu/enpl/bulletins/fallwebworm/fallwebworm.htm Accessed Aug 21, 2006.
Wagner, DL. 2005. Caterpillars of eastern forests. Princeton Univ. Press.
Warren, LO and M Tadic. 1970. The fall webworm, Hyphantria cunea (Drury). Arkansas Agric. Exp.Sta. Bull. 759.
