Defoliators
> Fall Webworm
Pest: Fall Webworm (Hyphantria cunea (Drury))
Order: Lepidoptera
Family: Arctiidae
Host Plants:
Dozens of different hardwood species act as hosts for this
insect; Birch (Betula ), Lilac (Syringa ), Crabapple
(Malus
), and Cherry (Prunus ) act as some of the more common hosts
in the Northeast.
Description:
The most notable aspect of this pest is the unsightly silken
web that it produces. Many times, there are many of these webs per
tree. These webs are started near the tips of the branches and gradually
are extended down the branch towards the trunk. The caterpillars
cover and skeletonize the foliage as they proceed. The adult moths
are white and are rarely noticed or recognized except to the trained
eye. Larvae are pale yellow and hairy. Injury is mostly aesthetic.
Life Cycle:
Adults are active from May into July and females lay small clusters
of eggs on the undersides of the foliage. The newly hatched larvae
appear by mid-July and begin to form silken webs around the foliage.
Many caterpillars will occupy one tent or web. Larvae feed within
the protection of the silken web and expand it downward toward the
trunk of the tree throughout July and much of August. Pupation occurs
on the ground or in the leaf litter in cocoons.
GDD for the larval stage is 1266-1795
Management Strategies:
Small trees may be completely covered with silk and totally
defoliated. However, injury happens late in the growing season,
and if the tree is not under previous stress, most of the injury
should be aesthetic. Newly forming webs (mid-July) can be mechanically
removed or treated. Bacillus thuringiensis (B.t.) is effective
on the younger larvae. Never use fire to burn webs out of the trees.
Fire can be extremely detrimental to the bark of the host plant
and has the potential to cause much greater long-term injury than
the fall webworm ever could.
Images:
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An individual web of the fall webworm.This one web may contain
dizens of caterpillars. Oftentimes, there are many webs on
one host plant. (R. Childs)
Several fall webworm caterpillars within their silken web
feeding on the host plant foliage. (R. Childs)
A small tree that is heavily covered with silk from the fall
webworm. This situation is very unsightly but mostly aesthetic.
(R. Childs).
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Defoliators
index:
Armyworm
Asiatic Garden Beetle 
Bagworm
Cankerworms
2006
Caterpillar Update
Eastern Tent Caterpillar
Fall Webworm
Forest Tent Caterpillar
Gypsy Moth
Japanese Beetle
Larch Casebearer
Lily
Leaf Beetle
Mimosa Webworm
Viburnum Leaf Beetle
Winter
Moth - ID & Management
UPDATED! Winter
Moth Overview
Winter
Moth Project - Biological Control in MA
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