DATE:   10/3/96
WRITER: Dr. Clyde Gorsuch, (864) 656-5043
 
Those Webs Now In Trees
Made By Fall Webworms

     CLEMSON -- Anyone driving around South Carolina now can't
help but notice webs in many trees dotting the countryside. Some
trees appear to be wrapped almost entirely with webs.
     The webs contain fall webworms, a pest that attacks more
than 120 varieties of fruit, shade, and woodland trees. Among
their favorites are apple, peach, pecan, black walnut, birch,
elm, hickory, poplar, white oak and willows. Occasionally they
attack roses and other shrubs. 
     Damage is much like that of the eastern tent caterpillar
which appear in early spring. But fall webworms make their nests
over the end of branches, never in tree crotches like the eastern
tent caterpillar does. 
     Initially the web covers a few leaves on a branch. As larvae
grow, entire branches may be infested. Webs often are 2-3 feet
long. The larvae eat entire leaves except for the midrib and
veins.   
     Full grown larvae are about an inch long and are very hairy,
with pale yellow stripes along the sides. These worms overwinter
as pupae in cocoons under trash on the ground or under loose
bark. White moths emerge from May to August. Since adults emerge
over several weeks, not all webs start at the same time.
     White eggs are laid in masses on the undersides of leaves.
As soon as they hatch, larvae begin to spin webs over the foliage
and feed on the enclosed leaves. The web grows as larvae grow
and eat foliage. Larvae remain clustered, usually not crawling
away from the web until ready to pupate. 
     Although the webs are unsightly, they usually do little
serious damage to plants because defoliation occurs in late
summer when deciduous trees and shrubs are going dormant.  
     Fall webworms have many natural enemies that ordinarily keep
the numbers down. But every few years the numbers increase and
trees become heavily infested. 
     For small trees, webworm nests can be cut out and destroyed.
A common practice -- burning nests in the tree -- isn't
recommended. Several serious fires have been started by people
doing this.  
     Spot treatment with chemical pesticides is effective when
applied in June as larvae start to make webs. Where infestations
are severe, spray the entire tree to avoid having to repeat the 
treatments.  For control recommendations, call your county
Extension office.  
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     If you have gardening questions or comments, write to 
Agricultural News & Publications, Clemson University, A-101
Poole Agricultural Center, Box 340311, Clemson, S.C. 29634-0311.
                             END