Wheat midge update in North Dakota
click image to zoom The adult wheat midge is an orange-colored, fragile, very small insect approximately half the size of a mosquito. It is about 0.08 to 0.12 inch (2 to 3 millimeters) long with three pairs of long legs. It has a pair of wings, which are oval, transparent and fringed with fine hairs. Two eyes are conspicuous and black. Be careful not to confuse the lauxaniid fly with wheat midge. The lauxaniid fly is yellowish brown, larger and more robust - about 1/10 to 1/6 inch (2 to 4 mm) in length - than the wheat midge. It also actively flies above the wheat canopy during the day and early evening. In contrast, the wheat midge flutters from plant to plant only in the evening. At night, the lauxaniid can be observed resting in the wheat canopy in a horizontal position with its head pointing down in contrast to the wheat midge, which rests with its head pointing upward.
click image to zoom The parasitic wasp, Macroglenes penetrans, plays an important role in keeping wheat midge in check naturally most years by killing the wheat midge larvae. The average parasitism rate for the wasp was 19 percent in 2011, compared with 17 percent in 2010 and 13 percent in 2009. Parasitism ranged from 0 percent to 100 percent across the state, with the higher rates occurring in areas where midge populations have been high the past year. More than half of the samples in 2011 (52 percent) had zero parasitism, which could cause wheat midge populations to increase in future years. Parasitic wasp populations should be conserved by spraying insecticides only when necessary, and avoiding any late insecticide applications (after 50% flowering) to minimize any negative impacts on the parasitic wasps, which are active at that time.
The soil samples were collected by NDSU Extension Service agents in the fall of 2011. The wheat midge soil survey is supported by the North Dakota Wheat Commission.