Swede midge identified

July 25, 2012 - Issue 22

In the northeast this year the racemes appeared normal except that some flowers had fused petals that did not open, suggesting a later infestation that should limit any impact on yield. Source: Julie Soroka, AAFC

Swede midge larvae in flower. Source: Julie Soroka, AAFC

Swede midge larvae. Source: Julie Soroka, AAFC

Swede midge larvae have been found in misshapen canola flowers from fields in the northeast region of Saskatchewan. Swede midge is not new to this region, as Canadian Food Inspection Agency personnel caught small numbers of adult swede midge in pheromone traps in the northeast (Nipawin and Melfort) and east central (Yorkton) areas of Saskatchewan in 2007. However, prior to now plant symptoms produced by their feeding activity have only been observed in canola fields in eastern Canada.

Canola fields in the Codette, Nipawin and Carrot River areas surveyed on July 18-20 were found to contain midge larvae. Symptoms included aborted flowers or flowers with petals apparently fused or glued together, and misshapen, stunted or sometimes missing pods. Based on the experience in Ontario, where the pest was first found in the year 2000, damage symptoms depend on the growth stage of canola when feeding occurs, and the intensity of feeding. If larvae attack pre-bolting canola, the growing point may become necrotic and bolting might not occur. Damage to a bolting stem may cause a “palm tree” effect, with a shortened raceme crowned with a bouquet of pods radiating out from one point rather than along a typical raceme. After full flowering swede midge does not impact canola yields. In the northeast this year the racemes appeared normal except that some flowers had fused petals that did not open,  suggesting a later infestation that should limit any impact on yield. When dissected, the flowers contained small larvae. Small, misshapen, or missing pods occasionally were found below the infested flowers.

Canola Watch