Wheat midge damage occurs regularly in Alberta, Saskatchewan, Manitoba, and southern British Columbia. This year in particular it will be important to scout for midge because the ideal conditions — delayed seeding and high moisture — create a high risk situation says Scott Meers, of Mayland Consulting in this episode of Wheat School.
The upside to the situation is that there’s not a large population of wheat midge this year but in Alberta and Saskatchewan there will be hotspots to look out for. “Crops that are slow growing seem to be lining up better with the wheat midge population for 2020,” says Meers.
The crop staging to scout for wheat midge is between heading, up until anthesis or flowering. Don’t use a sweep-net! “Sweeping is drastically infective,” says Meers, “that time of evening when you feel that moisture coming up off the soil, that’s the ideal time to look for wheat midge,” he says. Wheat midge look like miniature orange mosquitoes, will fly like a mosquito and hover around you, but you need to see them land on plants to be sure if it’s a midge or not.
Wheat midge can be confused with lauxanids, which are a little larger than wheat midge, are active during the day and the evening, and when they land on a plant, will sit horizontally or facing downwards to the ground. Wheat midge rest on plants with their heads pointing upwards.
The parasitoid wasp, Macroglenes penetrans, is a beneficial insect that you can use a sweep net to identify; however, the benefit of its presence could take a while. It takes a full year for the life cycle of the wasp to catch up to the wheat midge, so we typically don’t get any help from them until the next spring. The wasp will lay an egg in the wheat midge egg and hangs around in the wheat midge right up till pupation of the midge the next spring. Then it will feed on the midge.
Economic thresholds for wheat midge are fairly well defined says Meers— one wheat midge in five wheat heads for yield protection. If you’re worried about grain grade protection the threshold is one wheat midge in every ten heads. Check several spots in the field to get a representative sample.
Timing for spraying is quite critical, need to check closely but spray almost immediately. The most effective management option for wheat midge is actually midge tolerant varieties of wheat, Meers adds.