|The Alberta wheat midge forecast for 2011 shows an increase in wheat midge risk for the coming crop year. There are pockets of moderate to high midge risk through much of central and southern Alberta. Midge is now found 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. Producers throughout the midge area will need to monitor their fields carefully in 2011. |
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The 2010 fall survey sampling was performed at a slightly enhanced level over the previous year and included almost all the municipalities in central and southern Alberta. In southern Alberta irrigated wheat was the focus of the survey. In total 223 samples were taken in 44 different counties. The larval cocoons are washed out of the soil samples and counted, and then dissected to determine if they are parasitized. The midge density on the forecast map is adjusted for parasitized larvae.
The forecast is not intended to take the place of individual field monitoring. The forecast for Alberta shows an increased risk of midge damage. 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 (when the wheat head becomes visible as the boot splits until mid-flowering (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 over-wintering survival of the midge, the survey and map provide a general picture of existing densities and the potential for infestation in 2011. Climatic conditions, mainly temperature and moisture, will ultimately determine the extent and timing of midge emergence during the growing season. Temperature and wind play critical roles in egg-laying activities of the adult female midge.
Life cycle information
Economic thresholds for orange blossom wheat midge
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 will ultimately rise and fall 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.
Updates of current conditions and wheat midge emergence will be available through the Ag-Info Centre (310 FARM) during the 2010 growing season.
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, County of Leduc, Mountain View County, and the Municipal District of Wainwright. All samples were processed by Alberta Agriculture and Rural Development with financial support from Dow AgriScience.
Follow this link to the Agriculture Canada tri-provincial forecast maps. Please go to the drop-down menu to locate the wheat midge map.
Follow this link to view the 2011 insect forecast video presentation.