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Swede Midge Taking its Toll on Canola in Ontario

By Rebecca Vandersleen, Farms.com

The northeastern area of Ontario has felt the influence of swede midge, a pest that can heavily impact the growth of canola.  This is why Ontario currently has less than 30,000 acres of planted canola, an area that once grew approximately 80,000 acres.   midge can also affect any plants in the cruciferous vegetable or weed family such as cabbage, stinkweed, wild mustard, kale, and broccoli.  

Over the past few years, swede midge has seriously damaged New Liskeard, Ontario canola crops and this season a large outbreak has taken place in Temiskaming, Ontario.   Traps put out would individually catch over 800 swede midge flies.  Canola growers in Temiskaming have been warned to switch out canola from their crop rotation for 3 years in the hopes to put a stop to this pest outbreak.  Some farmers have started to grow faba beans, soybeans, or even flax in its place.  Swede midge has also been spotted in central and southern Ontario; however, the population has not been anywhere as drastic as Temiskaming’s outbreak.  

This pest is native to Asia and Europe and was first sighted in Ontario in 2000.  The main problem with swede midge is that it is not easily controlled.   The adult life as a small, light-brown fly only lasts 1-4 days, which makes chemical treatment extremely challenging. During this short life, a female fly can lay as many as 100 eggs. The highest emergence rate of adults for the first generation occurs in the beginning of June.  It has been noted that up to 5 generations can intersect with one another throughout the growing season, making many pesticide treatments ineffective.  This pest will overwinter in cocoons and can continue their growth the following spring; however, sometimes the cocoons will overwinter for 2 seasons or more before pupating.  Spotting larvae can also be difficult as they are transparent and feed at the plants growing point, which also makes the use of contact insecticide inadequate.   This pest thrives in wet environments, and does not often do well in droughts.  

While swede midge recognition might be a challenge, the damage it causes is undeniable.  If eggs are laid close after the emergence of the canola seedlings, the larvae can completely kill the plant.  If eggs are laid after this stage, symptoms often include fused flowers and closed or swollen buds.  The pest has been known to completely change the makeup of the plant, creating twisted and disfigured tissue.  The best way to deal with this pest is to practice crop rotation; however, this does not always completely rid swede midge from the area.   Their population can grow very quickly if not closely monitored.  

While the acreage of canola planted in Ontario is currently low, the hope is that more can be grown again in the future.  Growers often prefer to have canola in their crop rotation as it has an earlier harvest time compared to a replacement such as soybeans, meaning it fits well with winter wheat.  Canola can also increase soybean yield when put into a 3-crop rotation with corn and soybeans.  However, before this can happen, swede midge needs to be successfully controlled throughout Ontario so that another devastating outbreak can be avoided.  
 

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