Tuesday, September 14, 2010

A Webworm Horror Story

Last Sunday I decided to enjoy the beautiful fall weather and eat my lunch outside. About halfway through my sandwich, I glanced up to see something fuzzy crawling down my bangs onto my nose – UGH! It was a fall webworm – you know, those nasty hairy caterpillars whose giant webs appear on tree branches every fall? There seems to be a bumper crop this year – caterpillars are crawling on everything: across yards, along sidewalks, up walls, on decks and porches… you get the picture. When I went outside to eat, I purposely positioned my chair away from the trees to avoid them (and to avoid the occasional falling walnut – ouch!). This fellow found me anyway and sort of put me off my lunch.

Description of Damage
In the grand scheme of things, fall webworms do not do a tremendous amount of permanent damage, although the webs are definitely unsightly. Caterpillars feed on leaves inside the webs, gradually enclosing more foliage as they grow. Heavy infestations may defoliate a tree but rarely kill it. Over 100 species of trees play host to these voracious pests, but here in central Virginia, they seem to prefer nut and fruit trees, such as walnut, pecan, cherry and crabapple.

Life cycle
The adult moth is snow white, often with dark spots, and somewhat hairy (not surprising, considering the caterpillar). They lay their eggs on the underside of leaves in May through July. The larvae hatch in about 2 weeks and immediately begin to spin webs and feed on leaves. Pupation occurs after 4 to 6 weeks of spinning and feeding and can usually be found in leaf litter or just below the surface of the soil. In the South, we are especially lucky - we get at least 2 generations per year!

Control is not necessary; however, you may not be able to tolerate the unsightly mess. If you do decide to take action, mechanical control is best. When you can reach them, prune branches containing webs and destroy them. Chemical control must be done when webs and larvae are small, no later than July, but it is not necessary. If you are lucky, birds and other natural predators may come to your yard and do the job for you!

Just remember – do not eat lunch under the webworm tree…

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