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April 11, 2007

Eastern tent caterpillar has hatched and is numerous in southern Illinois from Mattoon south. Tents already range from 2 to 6 inches long, reflecting the length of time during which various egg masses hatch. Their eggs hatch at and after leaf emergence on crabapple and other rose family hosts, but they do not appear to be numerous in central Illinois. Bacillus thuringiensis kurstaki (Dipel, Thuricide) is very effective against this insect when sprayed onto the foliage. Pyrethroid insecticides are also effective, but care should be taken not to spray blooming plants, to avoid harming bees and other beneficial pollinating insects. The caterpillars feed at various times during the daytime but are all inside the tent at night and on cloudy or rainy days. At those times, pruning off the tents is an effective control.

European pine sawfly should have hatched in central and southern Illinois. Look for masses of greenish worms on the foliage of Scotch, Mugo, and other pines. Hand-removal is effective, as are sprays of carbaryl (Sevin) and pyrethroid insecticides. Sawflies are the larvae of wasplike insects. Because they are not caterpillars (larvae of butterflies or moths), Bacillus thuringiensis kurstaki is not effective against them.

Zimmerman pine moth can still be controlled in northern Illinois with sprays of permethrin (Astro) or other pyrethroids on the trunk. In central and southern Illinois, it is probably already too late to obtain control, but the recent cold spell may still allow effective control.

Spruce spider mite and other conifer-feeding spider mites, such as pine mite and juniper mite, should be controllable throughout the state. Hold a piece of white paper under infested branches and strike the branch sharply to knock the mites onto the paper to verify their presence before spraying. Mites that streak green are feeding on the tree; those that streak red are predatory mites feeding on the harmful mites. The presence of many predatory mites may make spraying unnecessary. Acequinocyl (Shuttle), bifenthrin (Onyx, Talstar), insecticidal soap, spiromesifen (Forbid), or summer spray oil should be effective. Be sure to get thorough coverage with the spray.

Author: Phil Nixon


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