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Scouting Watch

May 25, 2005

Black turfgrass ataenius is a small, 1/4-inch-long grub that feeds primarily in highly maintained and irrigated turf such as golf courses, being most common in the wetter areas such as greens, as well as green aprons and fairway swales where water collects. Although this grub is found in home lawns and other turf, it is very unusual to have high numbers. The 1/4-inch-long, cylindrical, brownish to black beetles overwinter and fly to golf courses at this time when bridal wreath spirea (Spiraea x vanhouttei) is in bloom. They are very obvious in the clippings baskets of greens mowers. If the beetles are numerous or you tend to have damage from these insects, apply imidacloprid (Merit) or thiamethoxam (Mach 2) to provide control of the larvae when they hatch a couple of weeks later.

Gypsy moth larvae were sprayed by the Illinois Department of Agriculture “Slow the Spread” program during the week of May 16 in northeastern Illinois. As of May 18, the caterpillars ranged from 1/4 to 5/8 inch long. They are just hairy and black when very young, but those 1/2 inch and larger were already showing reddish orange and blue spots down the back. Even in heavily infested areas, damage was slight but very noticeable on close inspection, with many small holes and leaf margins eaten. The oak foliage is mostly expanded, with plenty of leaf area for spray deposition. Bacillus thuringiensis ‘kurstaki’ (Dipel, Thuricide), spinosad (Conserve), diflubenzuron (Dimilin), and tebufenozide (Mimic) are recommended for control.

Bagworms should be hatching in southern Illinois, but it is still too early to treat. The young larvae spin out long strands of silk and blow from tree to tree for about 2 weeks after hatching. Any spray applications at this time will result in more larvae blowing onto the tree after the insecticide has broken down, requiring another treatment later. The damage caused at this time of year consists primarily of window-feeding, which is not very noticeable. On needled evergreens, fed areas will be light-colored from the surface of the needles being eaten away. Although these areas will turn brownish later, they will not be obvious, due to the relatively small areas of damage. We recommend treatment in mid-June in southern Illinois and early July in central and northern Illinois.

Author: Phil Nixon


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