Annual white grubs have been reported in Bloomington in a lawn treated with halofenozide (Mach 2) in May. Although both Mach 2 and imidacloprid (Merit) usually give 3 months or more of control, research indicates that either chemical fails occasionally. When the residue is several months old, this failure rate may be 10 to 15 percent of applications. Check turf treated in the spring to be sure that control has been obtained. If not, trichlorfon (Dylox) is a good rescue treatment that should kill the grubs within 3 days. We recommend treatment with Mach 2 or Merit in July for annual white grub or Japanese beetle grub to help avoid failure of older insecticide residues.
Black cutworm has been particularly numerous in recent weeks on golf course greens. There are several generations of black cutworm, so expect them anytime from early spring to late fall. Black cutworm damage is most likely in bentgrass because Kentucky bluegrass is a poor host. Surrounding greens with bluegrass can reduce injury on bentgrass greens. However, cutworms can live in the taller bluegrass and come onto the greens at night to feed on bent-grass. Feeding damage appears as round patches of closely cropped turf up to 3 inches across. These areas are so closely cropped than they commonly turn brown. Insectivorous birds--such as starlings, cowbirds, and robins--feeding on the greens or near them may also indicate cutworm presence and can seriously damage greens while pulling out the larvae. Spinosad (Conserve), pyrethroids, and other insecticides are effective in controlling black cutworm.
Sycamore lacebug is being found in high enough numbers to be a nuisance. This insect feeds on the underside of sycamore leaves, causing the upperside to turn whitish with stippling. The leaf underside has numerous tiny black spots, which are lacebug feces. The 1/8-inch-long, flattened adults with white, lacy wings are on the underside near major veins, along with the smaller, blackish nymphs. They rarely cause significant damage. If treatment is needed, pyrethroid and other insecticides are effective.