Orange wheat blossom midge (Figure 1) as a wheat pest has been off the front page as a major production problem in NW MN for many years. Populations in the region have been small enough that significant outbreaks and associated yield losses have been of small concern. However, we learned in the mid-90’s that given the right circumstances, this insect can increase its population rapidly and cause major yield losses in a very short time frame.
During the “Best of the Best” production programs in February, wheat midge was discussed as an insect pest of concern for the 2009 season. Reasons for this concern focused on the potential for delayed wheat planting due to excessively wet soils from the fall and the potential for spring flooding in the region. Delayed planting puts the crop at risk by delaying heading later into the summer. The crop then becomes at risk to infestation when heading coincides with adult wheat midge emergence. These circumstances contributed to the outbreaks of the mid-90’s.
Planting Date and the High Risk Window
Wheat planting was significantly delayed this spring (Figure 2). Approximately 60 to 70% of the wheat acres were planted from May 10 through 31 in both Minnesota and North Dakota, a full 3 to 4 weeks later than normal when looking at the 4 or 5 year average. In addition, these acres were planted after the accumulation of 200 wheat midge degree days (DD).
This degree day accumulation range is associated with a high risk planting for wheat when related to wheat midge. Wheat midge larvae overwinter in the soil and they resume their development as temperatures increase in the spring. It has been demonstrated through field studies that wheat fields planted between 200 to 600 wheat midge DD will be heading when adult midge begin to emerge from the soil. Since wheat is at greatest risk to midge infestation during heading, farmers and consultants should identify fields planted during this time and plan to scout those fields for the presence wheat midge adults.
The dates associated with the degree day risk window vary from south to north (Figure 3). In fact, in the northern most counties, 600 DD has not been reached yet.
Monitoring Weather and Degree Day
You can track wheat and midge development in northwest MN and all of ND on the web at the NDSU weather project site for NDAWN at:
Under Applications, select wheat, then either wheat or midge degree days. By selecting your nearest weather station and setting your planting date, you can receive a report showing crop stage, midge development, and indication of infestation risk.