Favourable conditions found for wheat midge

Research suggests that yield losses can be as high as 15 percent in wheat fields where a single adult midge is observed for every four to five wheat heads. | File photo

Producers advised to begin scouting in late June and early July as hot spots are identified in Saskatchewan and Alberta

Canada Day is just around the corner, a time of celebration for many, but for farmers it’s also time to check for orange blossom wheat midge.

If conditions are favourable, the tiny insects will be hard at work, laying eggs that could take a significant bite out of the bottom line.

Canada Day typically marks the time of year when wheat growers should monitor for adult wheat midge activity.

According to the Prairie Pest Monitoring Network (PPMN), wheat growers in risk areas should begin scouting their fields in late June and early July, at the time that wheat heads are beginning to emerge from the boot.

Scouting should occur on calm, warm evenings, at dusk, when the female midge can be observed flying and laying eggs on developing spikes.

Adult midge are not active during the day.

A complete scouting protocol can be viewed on PPMN’s website here.

“Wheat midge adult emergence is typically quite well co-ordinated with the stage of wheat development that they need to lay their eggs,” said Meghan Vankosky, an entomology expert with Agriculture Canada.

“That’s usually into late June or early July, where the wheat heads are emerging but before they’ve started to flower.”

Wheat midge can cause a lot of damage under the right conditions.

Some research suggests that in wheat fields where a single adult midge is observed for every four to five wheat heads, yield losses can be as high as 15 percent.

To monitor insect levels and prevent such losses, Vankosky and other entomologists across Western Canada collect soil samples every fall from harvested wheat fields.

Soil samples are examined and assessed for the presence of unparasitized or viable wheat midge cocoons.

Those cocoon numbers are the basis of regional wheat midge forecast maps that are published each year.

The 2021 wheat midge forecast map can be viewed online here.

It shows potential hotspots in various parts of Saskatchewan, as well as northeastern Alberta, between Lloydminster and Edmonton.

To further assess the wheat midge risk, PPMN experts use models to estimate the likelihood that cocoons in the soil will complete their life cycle and produce egg-laying adults.

“Wheat midge require a certain amount of soil moisture in the spring… to complete their development so in areas where it’s been really dry all spring, that risk could be reduced,” said Vankosky.

Based on soil moisture levels over the past few weeks, conditions in some areas have been favourable for midge development.

An in-season larval development map that illustrates the percentage of the larvae likely to produce adult insects can be viewed here.

“Based on the moisture that we’ve received so far this spring, we’re able to predict now where it’s wet enough that wheat midge are probably going to proceed with their life cycle,” Vankosky said.

“In our latest (larval development) map, we’re starting to see some areas around Edmonton and around Regina, and up into the Peace River Region where there has been adequate moisture to probably trigger that wheat midge development.”

“If you’re farming in an area where it’s red on the annual wheat midge forecast map and where it’s getting to be yellow or red on the (in-season) development map, then those are definitely going to be areas where there could be elevated risk and farmers will need to scout.”

Scouting for wheat midge can be tricky.

Populations are estimated by counting the number of adult insects present on emerging wheat heads.

Counts should be taken at various locations in the field.

Crops should be assessed every 24 hours from the beginning of head emergence to full-anthesis.

The quality of a population estimate increases when midge numbers are counted for additional wheat heads.

Beneficial insects should also be considered.

Parasitoids that prey on midge eggs may be present in wheat crops and can be assessed using random net sweeps.

The parasitoids search out and parasitize wheat midge eggs that have been laid in developing wheat heads.

Female wheat midge lay eggs on wheat kernels, either alone or in groups of three to five.

An adult female lives for four to five days.

Eggs typically hatch in five to seven days.

After hatching, the larvae crawl to the surface of developing kernels and feed for two to three weeks.

If population densities exceed recommended economic thresholds, chemical controls may be necessary.

There are different economic thresholds for grain quality and yield.

To maintain optimum grain grade, the economic threshold is one adult midge for every eight to 10 wheat heads during the stage when crops are susceptible.

To prevent yield losses, the economic threshold is one adult midge for every four to five emerging wheat heads.

Alberta Agriculture has produced a video containing tips and techniques that can be used when scouting for wheat midge.

The video can be viewed online here.

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