The wheat midge (Sitodiplosis mosellana) is a pest found in wheat that can have significant impacts on your yields and grain quality.
These insects overwinter as larvae and emerge as adults from their pupal stage in late June to early July (typically 600-900 growing degree days (GDD), ask your agronomist how many GDD`s we have received or check farmzone.com). The female wheat midge typically have a life span of only a week, but in this week they can lay an average of 80 eggs. These eggs then hatch 4-7 days later and the larvae begin feeding on the developing kernel, the damage results in shrunken kernels or no kernels at all. These kernels can appear to simply be frost damaged so be aware of this. The females only lay eggs in the evenings (8:30-9pm) when the wind speed is less than 10kmh (very small, weak fliers) and when temperatures hover around 15 degrees celcius. During these conditions are the best times to scout for wheat midge. The threshold is 1 midge per 4-5 heads before or when a minimum 75% of heads are emerged to just before flowering then you should be making an insecticide application. For quality the concerns the threshold goes to 1 midge per 8-10 heads. If you have reached the economic threshold in your field then an application of insecticidal application is warranted. Lorsban (or chlorpyrifos products) and Cygon/Lagon (dimethoate) are the two registered products. Lorsban will give you a 48-72 hour residual as well as taking out already laid eggs. Since these pests are more active in the evening, this is the best time to spray for them.
Be sure not to confuse the wheat midge with the Lauxinid fly which are larger and a duller orange. These insects are also active during the day where as wheat midge tend not to be. When they are at rest on a wheat head their heads heads will point down whereas wheat midge tend to have their heads pointing towards the sky.
There has been some new varieties of wheat that are resistant to wheat midge as the breeders tweaked the wheats sm1 gene which essentially makes the kernel acidic and repulsive to the wheat midge larvae meaning the larvae starve to death. There is 10% of the seed that is still susceptible to wheat midge attacks, this is simply to keep the midge from becoming resistant to the sm1 gene in a short period of time; because of this it is expected that this technology should hold off the midge for 80-100 years. These varieties are something to consider for 2014 if you constantly find yourself with midge concerns.
Provincial agriculture departments typically release a forecast map to show locations of higher activity, so check them out and see where you stand. Even if you aren’t in a “hot spot”, take an evening to check your fields!