The Alberta wheat midge forecast for 2021 is now available and, depending on where you farm, there’s good news and bad news. The good news is that southern Alberta continues to be at low risk. However, the bad news is that areas in central and eastern Alberta are at risk for high midge pressure in 2021. In addition, issues may arise in the Peace region if conditions are conducive to midge development, and pockets south and west of Edmonton may see higher pressure this year.
Forecasts are based on larval density in the soil. Larvae can stay dormant in the soil for several years, but growing seasons with above average rainfall will favour adult emergence. Also, midge damage in previous crops can be an indicator of future pressure.
Scouting for wheat midge is possible but can be difficult to do because they are particular about when they are active. Adult midge prefer calm, warm evenings, and there is a relatively small window when they are laying eggs. The other challenge is when you do find them, it requires an insecticide pass to control them if a midge tolerant wheat variety was not grown. We generally want to avoid insecticide applications, and access to the most effective insecticide for wheat midge, chlorpyrifos, is becoming more restricted.
While insecticides are an option, control is often unreliable, and it’s difficult to get the timing right as adults can emerge over several weeks. Insecticides can also reduce numbers of beneficial insects, such as the parasitoid wasp Macroglenes penetrans.
The first line of defense against wheat midge is to seed midge tolerant wheat varieties. These varieties have the Sm1 gene which stops midge larvae from feeding on wheat kernels. All midge tolerant wheat varieties are sold as varietal blends, i.e., 10 per cent of the seed is a variety that’s not midge tolerant. This is an important characteristic which slows midge communities from overcoming the tolerance trait by reducing selection pressure for resistant individuals.
Midge tolerant varietal blends come with a stewardship agreement, which allows farm-saved seed only one generation past certified. This is important because it ensures the interspersed refuge of the non-midge tolerant variety remains at a sufficient density.
If a grower is in a high-risk midge area, a midge tolerant variety should be considered. If there isn’t a history of midge pressure in your area, then it may not be necessary to opt for a midge tolerant variety. This is different from an area with a low risk forecast for midge because these areas may have had higher pressures in the past and, if conditions are right, it’s possible they will see high midge pressure this year.