Grainswest - Spring 2023

Spring 2023 grainswest.com 13 The work of wheat stem sawfly can be visually striking but difficult to judge by eye. In areas where they are prevalent, farmers should count cut and uncut stems to quantify crop damage. BY IAN DOIG • PHOTOS COURTESY OF SHELLEY BARKLEY settle in below soil level. Farmers in sawfly territory tend to cut wheat higher. The use of a stripper header allows the beneficial wasp to overwinter. With little effective insecticide avail- able, additional cultural controls are necessary. Farmers in the area grow solid stem wheat, adjust their rotations and seed larger fields. Barkley also encourages farmers to do their own counts. Pick four one-metre row sections along the field margin and count both cut and uncut stems. The damage can be visually strik- ing, but the percentage of affected plants is difficult to gauge by eye. “This will give you a better understanding of what’s going on in your field,” said Barkley. WHEAT MIDGE “We’re very fortunate wheat midge has one of the most robust pest management monitoring plans,” said Jennifer Otani, AAFC pest management biologist and PPMN co-chair. Very dry conditions in 2021 may have caused the midge population to lie dormant that year. Cocoons were then prevalent enough in 2021 and 2022 wheat crop soil cores to cause concern in spring 2022. “We had almost perfect growing conditions for the midge cocoons,” said Otani. “And portions of the Prairies also had nearly perfect wheat development staging, such that midge emerging over- lapped with heading in wheat.” Once harvest is complete, Alberta Agriculture’s Barkley collects soil cores from approximately 325 spring wheat fields across Alberta. The annual survey samples three to six fields per county, including dryland and irrigated acres. At the Crop Diversification Centre South in Brooks, Barkley assesses the density of cocoons and whether they have been par- asitized by Macroglenis penetrans , a tiny beneficial wasp. Alberta and Saskatch- ewan ag ministries and PPMN publish midge risk maps online each January. “Based on those maps, farmers can decide whether they’re going to go with midge resistant cultivars,” said Otani. In spring, Vankosky and her PPMN colleagues continue to assess midge populations, which are very sensitive to early season conditions. They refine the forecast with the incorporation of Prairie environmental data to their modelling. Additional monitoring is carried out by AAFC Saskatoon entomologist Tyler Wist with the help of SeCan clients. These farmers voluntarily deploy pher- omone traps in wheat fields across the Prairies in late June and early July. This determines when the insects are on the move. Real-time activities of the trapping network can be tracked on Twitter at #midgebusters . “It’s a great educational tool to teach people about wheat midge,” said Wist. “It gives me a platform to answer questions directly.” Proving the value of the project, a Peace Country farmer reported collect- ing a lot of male midge. Wist asked him to check the wheat heads for females, which held three per head. The econom- ic threshold is one per five heads. The farmer rolled out the sprayer immedi- ately. Launched in 2021, Wist hopes the initiative will continue in 2023 with the addition of larvae counts. Dry conditions kept midge numbers low in 2021, but the insect rebounded. “In 2022, we learned you don’t turn your back on wheat midge even if a bad year is not in the forecast,” said Wist. “If condi- tions are right, they come roaring back.” “That program really helps producers time their in-field scouting,” said Otani. “We’re able to predict on a regional basis, but they can then follow up field by field.” Alberta Agriculture offers midge pheromone traps to Alberta farmers and agronomists. Users contribute counts to an accompanying app. This data on the insect’s prevalence and development fuels a live-feed map available at the Alberta Insect Pest Monitoring Network webpage. The map facilitates greater ef- fectiveness in field scouting. Pheromone trap use is on the rise, said Barkley, es- pecially in areas where the insect is most common, such as Beaver County and the Highway 16 corridor between Edmonton and Lloydminster. The fall 2022 midge survey indicated a mostly positive outlook. In the southern irrigation areas where moisture levels can benefit the insect, none were detect- ed. Just two fields were found to contain midge in Flagstaff County in 2021. The area tends to receive more moisture than dryland acres to the south, and midge did expand significantly across Flagstaff, Camrose and Beaver counties in 2022. A few were also found in Sturgeon County. Barkley suggested farmers in affected areas monitor their fields closely when wheat crops are at heading and are most susceptible to midge damage.