Wheat Midge Risk High in Saskatchewan

REGINA - Feb 20/06 - SNS -- This year's Wheat Midge Forecast Map indicates that densities of this insect pest have increased over much of the eastern half of Saskatchewan and will pose a high risk to crops, according to Saskatchewan Agriculture and Food Insect Pest Specialist Scott Hartley.

Wheat midge have been a serious problem for wheat producers since 1983, when they first appeared in Saskatchewan. This insect pest has gradually spread from the eastern half of the province to affect western regions, including North Battleford and Lloydminster. It has also expanded into Alberta.

"We had huge numbers during the late 1990s. In the early 2000s, the population was still high, but there has been a decline since, until now," Hartley says.

"For the past few years," Hartley goes on, "we haven't had very high numbers, which has moved the wheat midge off the radar as a serious pest. In the 2005 forecast, we started to note some higher populations of wheat midge again, largely in the south-east, but also northward along the Manitoba border. So we are back up to very serious infestation levels."

How these forecast maps are compiled is worth noting. Hartley explains that, in the fall, the survey is carried out by collecting soil core samples.

"The soil samples are washed; wheat midge cocoons are extracted and then dissected to check for parasite levels. Results show that, even after being corrected for parasitism, there are some high wheat midge populations, largely in the east central and south-east regions, and along the Manitoba border. It looks like midge will pose a reasonable threat to wheat producers across much of the eastern half of the province in 2006."

This rise in wheat midge levels can be attributed largely to climatic conditions that are more favorable to the midge, according to Hartley.

"This insect likes moist, cooler conditions. During 2001 to 2003, we had mostly hot, dry conditions that were probably responsible for the reduction of midge numbers. There are probably other factors, as well. For 2004-2005, the climate has been more conducive to a resurgence of the pest."

The 2006 forecast map is not very encouraging, although the forecasting techniques themselves are improving by leaps and bounds, notes Hartley.

A recent innovation is the identification of a wheat midge pheromone—a chemical that is released by a female to attract male midge. The research involved a joint project through Agriculture and Agri-Food Canada in Saskatoon and Simon Fraser University in British Columbia.

Hartley explains how this team has developed a monitoring system based on pheromone-baited traps set in the fields that would attract male midge and provide an indication of the prevailing midge levels.

"We are excited about this, as it is a positive step and an affordable tool for the future. The manufacturer, Phero Tech, is now working on establishing an economic threshold that could tell producers at what level spraying would be required."