Alberta’s wheat midge forecast for 2013 indicates an increase in midge risk. Pockets of moderate to high risk are found in central and southern Alberta. Throughout central and southern Alberta individual fields could have a high population even if the forecast in the area is low.
Producers should pay attention to midge downgrading in their wheat samples and use this as a further indication of midge risk in their fields. Wheat midge was confirmed in the Peace region in 2011 but the survey indicates that levels remain low there. Individual fields throughout Alberta may still have economic levels of midge. Each producer also needs to assess their risk based on indicators specific to their farm.
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The 2012 fall survey included wheat-growing areas throughout Alberta. In total 297 samples were taken from 57 counties. The survey involves taking soil samples from wheat fields after harvest using a standard soil probe. Larval cocoons are washed out of the soil using a specialized series of screens. 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. 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 to monitor their fields when the midge adults are flying and their wheat is in the susceptible stage. In all areas where midge is present growers are urged to monitor their wheat fields from wheat head emergence to anthesis (the susceptible stage). Regular field scouting on multiple nights in succession is important in understanding the population in a particular field.
Parasitism of midge larvae by small wasps (Macroglens penetrans) has been important in keeping wheat midge populations below the economic threshold in many areas. These beneficial wasps tend to thrive in warm, dry conditions. Parasite populations increase and decrease with changes in the midge population and are very important in moderating population levels in Alberta.
