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Scouting Watch

May 4, 2005

European pine sawfly has hatched throughout Illinois. These caterpillar-like insects have black heads and medium and dark green stripes, and grow to about one inch. They feed in groups on Scotch, Austrian, and other pines. When disturbed, everyone in the group rears up anterior and posterior ends in unison and regurgitates fluid from their mouths. They feed on the second- and third-year needles, being full grown by the time that the new needles from the candles emerge. They feed on the outer needle layers, leaving a brown central core that dries, curls, and drops from the tree. Thus, damaged branches will be needleless except for clusters of first-year needles at the ends of the branches.

European pine sawfly can be controlled by pruning off infested branches or spraying with acephate (Orthene), azadirachtin (Neem), carbaryl (Sevin), spinosad (Conserve), or other labeled insecticides. Because these are the larvae of wasplike insects and not true caterpillars, Bacillus thuringiensis ‘kurstaki’ is not effective.

Taxus mealybug are present at this time as young nymphs, which are susceptible to sprays of imidacloprid (Merit), insecticidal soap, or summer oil. Apply the soap or oil three times at weekly intervals. If you apply Merit, repeat the spray after 2 weeks. Taxus mealybug appear as white, cottony insects at twig crotches and at the base of needles. They tend to be found in more humid locations deep in foliage masses of repeatedly sheared bushes in landscapes and in tightly grouped nursery plants. Be sure to use a high-pressure spray to penetrate the tight foliage and contact the insects with the insecticide.

Japanese beetle soil application of imidacloprid (Merit) should be completed by the end of April to early May. Soil application of Merit takes up to 2 months to spread throughout trees and shrubs. With emergence of Japanese beetle adults occurring from late June in southern Illinois to early July in northern Illinois, that is only 2 months from now. Realize that with this application, some trees will still have beetles and damage, but the beetles on most of the trees will be controlled.

Author: Phil Nixon


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