2003 Wheat Midge Risk Outlook Low

The orange wheat blossom midge outlook continues to be positive. Based on wheat midge survey results from soil samples taken last fall, the overwintering population continues to remain low, even in northwestern North Dakota where problems with this insect have persisted in recent years.

None of the 200 fields sampled in the survey had healthy, overwintering populations of wheat midge larvae exceeding 1,200 larvae per square meter. This level of midge has been critical in past seasons.

Midge larvae were present in significant numbers at three locations: north-central Mountrail, central Ward, and northeastern Rolette counties. These small areas had cocoon counts that exceeded 800 per square meter, but larvae were parasitized at a rate as high as 75 percent. Parasitized larvae do not produce adult midge and therefore parasitism reduces the midge potential for the coming year in those locations.

As in previous years, areas where population estimates were above 500 midge larvae per square meter still require close vigilance by wheat growers.  These larval populations can lead to major economic infestations if the wheat crop is heading during adult midge emergence and environmental conditions are favorable for midge activity.

Weather conditions during the spring and summer are very important in determining if economic injury will actually occur.  If heading coincides with emergence of the midge and weather conditions are favorable for the female to lay eggs, producers will need to monitor fields, even in areas where the survey says populations are low, to determine if a pesticide application is necessary. High soil moisture, warm and calm conditions, and high humidity have all favored midge egg laying in past years.

This year’s early planting should be beneficial in avoiding midge damage as well: With early planting, wheat can reach the flowering stage before significant levels of midge have emerged.  Wheat is susceptible to midge infestation from the time the head emerges from the boot until 80 percent of the primary heads have anthers visible.

Peak midge activity occurs about 9 p.m., on evenings when air temperatures exceed 59 F and wind speed is less than 6 miles per hour. When temperatures are less than 59 F or wind speed is greater than 6 miles per hour, adults are not actively laying eggs on the primary wheat heads.

—Phillip Glogoza, NDSU extension entomologist

Fields Dry? Leave Stubble for Snow, Consider Fertilizing Next Spring
According to NDSU research, the difference between leaving upright stubble and leaving no stubble made a difference of between 1.1 inches and 2.15 inches of extra moisture. The studies averaged about 1.5 inches of extra moisture due to snow catch, which is influenced in part by surface roughness, but mostly by stubble height. Stubble left at 13 to 15 inches increased spring soil moisture by 1.45 inches compared to a 2 inch stubble height.

Separately, if you haven’t already applied fertilizer this fall, consider holding off until spring, especially if your fields are dry. Anhydrous ammonia may not seal properly in soil that’s too dry, says Duane Berglund, NDSU extension agronomist.