Issue 9, June 17, 2011
Bagworms were observed as newly hatched larvae in central Illinois about June 11. We reported last week of their being found in the Collinsville area on June 9. We expect hatch to occur in northern Illinois during the coming week. Remember that bagworms balloon from tree to tree as young larvae for a couple of weeks before settling down to feed. Treatment is recommended two to three weeks after egg hatch so that one application provides control.
Periodical cicada damage was reported from Effingham County on June 16. Damage was obvious on June 13 in northwestern Kentucky. The female cicadas slit stems to insert their eggs. This stem damage frequently results in the leaves dying farther out on the branch. Damaged stems are also susceptible to snapping off in the wind, resulting in numerous fallen twigs and hanging ones on the tree whose leaves also wilt and die. One-eighth to one-quarter inch diameter stems are preferred, but oviposition can occur in stems as large as two inches in diameter. Typically, egg-laying occurs within one foot of the stem tip, so the number of dead leaves is few per branch.
This damage is not significantly harmful to the health of larger, established trees. The twig loss results in increased lateral branching and bushiness of the foliage for a couple of years. As suggested in an earlier issue of this newsletter, the trunks of very small trees should be protected from damage with hardware cloth.
Fourlined plant bug probable damage has been reported on purple coneflower. Fourlined plant bug adults are about one-quarter inch long, flat-backed, and yellow with four black stripes down the back. The nymphs are present now; they are smaller and red and black. Both adults and nymphs are obvious on the foliage on examination. Their feeding on the foliage produces brownish to blackish, oblong areas that coalesce into large, elongated damaged areas. This insect also causes severe leaf damage to mint, chrysanthemum, coreopsis, veronica, artemesia, salvia, astilbe, cranesbill geranium, black-eyed Susan, and penstemen.
Because the bugs are exposed on the foliage, many contact insecticides provide excellent control. Insecticidal soap is commonly recommended due to its broad labeling; however, thorough coverage is essential as there is almost no residual activity. (Phil Nixon)