Figure 1. Orange wheat blossom midge.
A) larva inside the glume.
B) Adult resting on wheat head (note it rests with head pointing up).

Last year, Orange Wheat Blossom Midge (OWBM) larvae were recovered from a few hard red spring wheat fields in southern Minnesota, especially in and around the Dawson area. This is not necessarily a cause for concern, nor do we recommend treating for this insect without first scouting and establishing the population levels. We do not currently know the extent of the OWBM populations in southern MN, but thought a Heads-Up was in order. Most of the wheat in southern MN is close to heading and because degree day models predict approximately 50% of female midges that may be in that area will have emerged by late next week (June 21-23), it may be prudent to scout fields for OWBM.

Table 1. Degree day progress of OBWM life cycle

Orange Wheat Blossom Midge is a small, pinkish-orange fly resembling a small orange mosquito (Fig. 1). Adults emerge from the soil in last year's wheat fields over a 4-6 week period in mid-June to mid-July (around wheat head emergence/flowering) (Table 1). During the day, OBWM prefers to rest within the humid crop canopy and flies on warm, calm evenings. Females will fly between wheat heads in the evening when the temperature is above 59F and the wind below 6mph. Eggs are deposited on wheat kernels at or just before anthesis. Eggs hatch in 4-7 days and larvae feed on developing kernels within the glume (making it difficult to directly treat the larvae). Larvae feed for 2-3 weeks, until they are 1/8" – 1/4" long, and then drop to the soil in August after either rain or a heavy dew. They burrow into the soil and overwinter in cocoons in the soil. In spring, the larvae pupate and emerge as adults.

Scouting for OWBM is best done by visually inspecting fields at dusk (9-10pm), when females are flying between plants to deposit eggs. They are poor fliers and only take wing when the wind is below 6mph and temperatures are 59F or higher. Females fly in an irregular pattern over the canopy and tend to flutter between plants. Don’t confuse OWBM with Lauxanid flies, a much stouter yellow fly, more closely resembling a housefly and which has a much stronger, more direct flight pattern. Lauxanids tend to sit on plants horizontally or with their head pointing down where OWBM generally sits on plants with their heads pointing up. Examine at least 4 locations in each field and take an average of the number of females seen per head. If 1 female per 4-5 heads is found, and 30% to 80% of the wheat has headed, insecticide application will likely provide an economic return. Optimum control will be achieved if 70% of wheat has headed. If wheat is 30%-60% headed, some control will be obtained, but will be reduced. If wheat less than 30% of wheat has headed, wait up to 4 days prior to application. If more than 80% of wheat has headed, application is not recommended; either the larvae are already established within the glume and are protected from insecticide application or the wheat is no longer as attractive to adult midge and further infestation is unlikely (Table 2). Treatment decisions can only be made from visual scouting, trapping with sticky traps (e.g. paper plates covered with vegetable oil) do reveal if OWBM are present but do not provide a reliable estimate of population levels.

Table 2. Timing treatments for OWBM.

printer-friendly PDF version