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| The Alberta wheat midge forecast for 2012 indicates an increase in the range of wheat midge occurrence. Overall midge risk for 2012 will be lower than in 2011. Many areas show a lower wheat midge count in the annual survey. Some areas, however, show an increase over previous years. Pockets of moderate risk remain through much of central and southern Alberta. Throughout central and southern Alberta and there is the risk that individual fields could have a high population even if the forecast in the area is low. Wheat midge was confirmed in the Peace region in the past year although the survey indicates that midge levels remain low. Producers throughout Alberta will need to monitor their fields in 2012. | |
The 2011 fall survey included wheat growing areas throughout Alberta. The survey was expanded to include all dryland and irrigated wheat growing areas in southern Alberta. In addition, in response to reports of midge in the Peace region the survey was expanded to that area as well. In total 290 samples were taken in 59 different counties. The survey involves taking soil samples from wheat fields after harvest using a standard soil probe. The larval cocoons are then washed out of the soil samples using a specialized series of screens. The larvae are counted, and then dissected to determine if they are parasitized. The midge density displayed on the forecast map is based on viable (live, non-parasitized) midge larvae.
This forecast is not intended to take the place of individual field monitoring. The forecast for Alberta shows areas of risk of midge damage for 2012. It is important to note that over such a wide range, populations in individual fields can be and often are highly variable. Producers should plan on monitoring their fields when the midge adults are flying and the wheat is in the susceptible stage. In all areas where wheat midge is present growers are urged to monitor wheat fields during the susceptible period (from when any part of the wheat head is visible until anthesis). Regular field scouting on multiple nights in succession is important in understanding the population in a particular field.
Although a number of factors influence the over-wintering survival of the midge, the survey and map provide a general picture of existing densities and the potential for infestation in 2012. Climatic conditions, mainly temperature and moisture, will ultimately determine the extent and timing of midge emergence during the growing season. Temperature and wind also play critical roles in egg-laying activities of the adult female midge. The level of damage from wheat midge is determined by the synchrony of wheat midge emergence and the number wheat midge and timing of wheat susceptibility.
Parasitism of midge larvae by small wasps (Macroglens penetrans) has been important in keeping wheat midge populations below the economic threshold. These beneficial wasps tend to thrive in warm, dry conditions. Parasite populations increase and decrease with changes in the midge populations and are very important in managing population levels in Alberta.
It is important to note that once midge has established in an area it is unlikely to ever completely disappear. Low lying and moist areas in a field provide a refuge, enabling the population to survive even when conditions are not favorable in the rest of the field. These low level populations, however, also help sustain a population of natural enemies.
The wheat midge survey was conducted by Alberta Agriculture and Rural Development with assistance from Lakeland Applied Research Association, Battle River Research Group, Chinook Applied Research Association, Northern Peace Applied Research Association, Leduc County, Mountain View County, Parkland County, County of Two Hills, M. D. of Wainwright, Wheatland County and staff from Agriculture and Agri-Food Canada, Beaverlodge and Fort Vermilion. All samples were processed by Alberta Agriculture and Rural Development with financial support from Dow AgriScience.
Updates of current conditions and wheat midge emergence will be available through the Ag-Info Centre (310 FARM) during the 2012 growing season.
Alberta Insect Pest Monitoring Network 2011 Annual Report
Follow this link to return to the Alberta Insect Pest Monitoring Network home page.
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