Wheat midge is a troublesome pest that can reduce yields and lower the grade of cereals at harvest.
It’s sneaky. Lower yields or grade caused by wheat midge are sometimes mistakenly blamed on drought stress or frost damage. Cereals showing wheat midge damage have kernels that shrivel, crack and become deformed. It’s the kernels where the wheat midge larvae feed.
Wheat midge is a problem around the world, wherever cereals are grown. The pest can exist for several years before it becomes a significant problem. However, if conditions are favourable (moist conditions in May that favour larval development and emergence of adults), populations can increase rapidly.
Scout for wheat midge every day from the time wheat heads become visible as the boot splits, until mid-flowering (anthesis). Drought seems to reduce wheat midge populations.
Scouting for wheat midge
- The peak period of flight of adult wheat midge is typically in late June to mid-July
- Inspect fields frequently from the time wheat heads emerge from the boot leaf until anthers are visible on the heads
- Adult females are more active on calm evenings when wind is less than 10 km/h and the temperature is above 15°C
- Scout 90 minutes prior to sunset until about 30 minutes after sunset, when female midge are most active
There are midge-tolerant wheat varieties that protect growers from damage caused by the orange blossom wheat midge. It is particularly important to scout wheat fields for midge if a non-tolerant variety is being grown.
How to count wheat midge
Estimate wheat midge populations by counting the number of adults present on four or five wheat heads in at least three or four locations. Highest numbers are usually found next to fields where wheat was grown in previous years or in low spots with more soil moisture.
Thresholds to maintain grade and yield
Economic thresholds can help you decide if it is worthwhile to spray. Determining the economic thresholds for wheat midge depends on your focus. If you care mostly about maintaining wheat grade and yield, spray when there is one adult midge per 8-10 heads. The shriveled, cracked wheat kernels caused by wheat midge larvae feeding will adversely affect your grain samples.
Thresholds to protect only yield
If maintaining yield is the only concern, spray an insecticide when there is at least one adult midge for every four or five wheat heads. If you don’t control the insect when pressure reaches this level, you could see wheat yields reduced by 15%. Of course, yield will be reduced even more if higher numbers of wheat midges are present.
When to spray Cygon® 480 AG insecticide
If adult wheat midges are present, spray Cygon® 480-AG insecticide when 25% of the wheat head has fully emerged from the boot but before flowering has begun. Cygon® 480-AG insecticide must be timed to control adults (it does not control eggs) so target the application within 24 hours of reaching the action threshold while the adults are still active.
The best time to apply Cygon® 480-AG insecticide is in late afternoon or evening when temperature exceeds 15°C and wind speed is less than 10 km/h. Increased water volume sprays will improve penetration into the crop canopy. If the wheat midge population persists, apply a second treatment three days after the first, provided the crop has not started to flower.
Wheat midge can reduce yield and quality, but good scouting and the proper insecticide treatment will help protect your crop.
Source: Province of Manitoba | agriculture - Wheat Midge (gov.mb.ca);