Wheat Midge Outlook Good for Saskatchewan

REGINA - Mar 19/03 - SNS -- There is a low threat from wheat midge this year in Saskatchewan, says insect control specialist, Saskatchewan Agriculture, Food and Rural Revitalization (SAFRR), Scott Hartley.

Even so, he reminds producers that the wheat midge forecast 2003 is a regional estimate. Under ideal weather conditions, even areas showing less than 600 midge per square meter could experience economic damage.

"The distribution of wheat midge as illustrated in the 2003 forecast map is based on cocoons present in soil samples collected in a 2002 fall survey," explains Hartley. "Although a number of factors influence over-wintering survival of the midge, the survey and map provide a general picture of existing densities and the potential for infestation in the coming year. Climatic conditions - mainly temperature and moisture - will ultimately determine the extent and timing of midge emergence during the growing season.

"For this reason, all wheat producers should monitor crops while the midge are flying and the wheat is in a susceptible stage, which is from emergence of the wheat head from the boot until flowering begins."

The 2003 forecast map indicates infestations of less than 600 midge per square meter over most of the province. The exceptions are the higher densities in pockets east of Regina near the Manitoba border, and near Lloydminster. Other exceptions are the areas of no infestations around Melfort and in the south west and west central part of the province.

Infestations of over 600 midge per square meter may result in significant damage and yield loss. Wheat midge larvae feeding on kernels can affect final yield, grade and grain quality. Severely damaged kernels that are lost during threshing will lower yield, while less damaged kernels that are harvested will reduce grade.

"An insecticide application is recommended when the crop is heading and the adult midge density is one per four to five heads. To maintain optimum grade, insecticides should be applied when adult midge populations reach one per eight to 10 heads. Late insecticide applications should be avoided: not only are they not cost effective, they may adversely affect small parasitic wasps that act as biological control agents," says Hartley.

The parasitism of midge larvae by these wasps can keep populations below the economic threshold. Parasitism rates generally range from zero to 90% in Saskatchewan. The midge density on the forecast map is adjusted for parasitized larvae.

The Wheat Midge Forecast 2003 map may be viewed on SAFRR's Internet Web site. Agriculture and Agri-Food Canada monitors conditions during the growing season to determine the expected emergence and flight of wheat midge adults, and updates of current conditions will be provided during the 2003 growing season at all rural service centers.

The 2002 fall survey was conducted by Agassiz Scientific Limited and Agriculture and Agri-Food Canada (AAFC.) The survey was funded by Saskatchewan Crop Insurance and AAFC. The forecast was prepared by AAFC.

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