University of Illinois Extension
Bruce Spangeberg

These articles are written to apply to the northeastern corner of Illinois. Problems and timing may not apply outside of this area.

Stateline Yard & Garden

Watch for Sawflies & Tent Caterpillars

April 26, 2001

Even though this spring has featured plenty of cool weather, trees and shrubs are gradually leafing out. Two early season tree pests to be watching for are the European pine sawfly and the eastern tent caterpillar. Although populations may vary, these insects show up every year.

If a mugo pine exists in your yard, there’s a good chance you’ve encountered the European pine sawfly at some point. Branches on mugo pine appearing to move when you walk by is typically how people get introduced to European pine sawfly larva. They will feed on last year's needles, so will disfigure pines but are not likely to kill them. Mugo, Scots, and Red pine are among the favorite targets.

Control pine sawfly larva with carbaryl (Sevin) as soon as they appear. Instead of spraying insecticides, another possible option is to knock the larva off the branches with a stream of water or remove them by hand. Don't cut off infested branches, as the terminal bud will be removed and new growth will not appear on that branch in 2001. Pines should only be pruned by cutting back the new candle growth, which typically appears in June.

White, tent-like webs of eastern tent caterpillar may appear in crabapple, apple, cherry, and plum trees. Since it may consume most or all of the foliage, trees being defoliated so early in the season may become stressed. Do not mistake this insect for gypsy moth – which do not make webs in trees.

One control option is to carefully clip out the web in the evening or on a cold, cloudy day when the caterpillars are inside and destroy it. Another control option is to apply Bacillus thuringiensis (Dipel, Caterpillar Attack, etc.), a microbial insecticide that is very specific to the larva of butterflies and moths. Other types of insects, including beneficial insects, would not be harmed.


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