GrainsWest Fall 2019

Fall 2019 Grains West 12 THE FARMGATE IT’S ONE OF THE BIGGEST PEST threats to Alberta’s wheat farmers, but so small it’s hard to spot. Scarier still, if cur- rent control measures fail, there’s no Plan B to stop it. The orange blossom wheat midge is a delicate, bright-orange fly. It’s half the size of a mosquito. Yet these little flies have been known to cause yield loss of more than 50 per cent in Alberta’s wheat fields. Recent dry weather has further reduced already low populations of wheat midge, which prefer to hatch in wetter conditions. “We’ve had massive outbreaks in south- western Alberta and the central Peace in the past, but both of those outbreaks seem to have subsided and they’re at fairly low numbers,” said Scott Meers, an insect man- agement specialist with Alberta Agricul- ture and Forestry. Wheat midge strike just when the wheat heads typically emerge in late June to early July. The eggs they lay on the wheat heads hatch into hungry larvae, which feast on the kernels. Their feeding damages, reduces or consumes the wheat kernels. None of this changes the outer appearance of the wheat head but causes loss of grade and yield. Midge populations can “blow up” very quickly if given the right conditions, such as a couple of wet years, Meers added. “This year in central Alberta is kind of a perfect year for wheat midge so I expect to see a resurgence,” he said. To keep an eye on wheat midge popu- lations, Meers and his team take 300 soil samples across Alberta’s wheat regions every fall. Counting midge cocoons in the soil allows his team to gain an idea of the midge population in the area. The current low levels of wheat midge are due to an effective—but potentially vulnerable— management system built around midge- resistant strains of wheat. THE MIRACLE GENE Alberta’s main line of defence against wheat midge is a group of midge-resistant wheat varieties carrying the Sm1 gene. Wheat containing Sm1 reacts to wheat midge larvae attack by increasing natural acids in the kernels that cause the larvae to stop feeding. Acid levels return to normal before the kernels mature. So far, it is the only known gene to truly deter wheat midge. “The most effective way to deal with wheat midge if you’re in a wheat midge area is growing the resistant varieties,” said Bill Chapman, a crop extension specialist with Alberta Agriculture and Forestry. The Sm1 gene varieties became commer- cially available in 2010 and are a linchpin of the wheat midge control strategy. The last severe outbreak was in 2013 in the Peace region, when wheat farms in several counties were severely damaged by midge infestations. The yield losses were some- where in the 50 per cent range, said Meers. His team made a point of visiting farmers in the Peace region after the 2013 outbreak and advised them on how to deal with the pest, which the area’s farmers took to heart. “In the Peace, when we had that big outbreak many producers went to that midge-tolerant wheat and the results have been spectacular,” he said. “Their losses just went away.” VIRULENT MIDGE Yet this weapon against wheat midge could easily be lost if farmers don’t follow indus- try rules on using the Sm1 system, warned Chapman. Part of the fear is that if farmers Midgemitigation Industry works to devise a Plan B Femalemidges such as this lay eggs onwheat heads.