White Butterflies Swarm Canola Fields
As reported on the OMAFA website fieldcropnews.com, Ontario canola crops are at various growth stages, ranging from seedling to full bloom depending on planting time and region. Winter canola is now fully podded, and harvest is expected to begin soon in Essex and other southern counties.
Farmers are advised to stay alert for swede midge in spring canola. Though past years have shown low damage, adult numbers are rising again. In Dufferin County, traps caught over 100 midges between June 10 and 25. Swede midge injury was severe from 2012–2016 but has since declined. Factors such as dry springs, beneficial insects, and weather shifts likely contribute to this.
This pest affects canola and other Brassica species by laying eggs in plant growing points. The larval saliva breaks plant tissue, affecting stem growth and branching. Pheromone traps are used to time insecticide applications. Spring canola is most at risk during bud formation, so control may be needed between emergence and early bloom.
Winter canola is generally safe, as it bolts before midge emergence. Though adult midges have been seen in late summer, studies show minimal crop impact due to winter canola's growth cycle. Monitoring will continue this season.
White butterflies, adult cabbageworms, have been widely spotted in winter canola fields. Their larvae feed on Brassica leaves but not on soybeans, wheat, or oats. Damage has been minor so far, with no major leaf loss or larvae presence. Canola can tolerate up to 50% leaf damage early on. As blooming progresses, leaves play a lesser role in yield.
Farmers are encouraged to report pest activity and continue scouting young canola this summer and fall.
For more information about the swede midge or imported cabbageworm, please visit the Farms.com Field Guide Pest pages.
Photo Credit: gettyimages-ligora