Grainswest - Spring 2023

Spring 2023 Grains West 12 THE FARMGATE THOSE ORANGE AND RED, blob-like areas on insect survey maps are a farmer’s cue to action. Fields seeded with certain crops and located in and around these hotspots may require individual assessment and population control. Among cereal farmers, the most anticipated of these maps are those for grasshoppers, wheat stem sawfly and wheat midge. GRASSHOPPERS Prairie Pest Monitoring Network (PPMN) grasshopper survey work is carried out by collaborators from Agri- culture and Agri-Food Canada (AAFC), the three Prairie provincial agricultural departments and the Saskatchewan Crop Insurance Corporation (SCIC), agricul- tural fieldmen and additional volunteers. Each summer, agricultural fieldmen, who work for Alberta’s Agricultural Service Boards, conduct counts along road allowances within every Alberta munici- pality. This data is then processed by Shel- ley Barkley, an Alberta Agriculture and Irrigation insect technologist. It is then forwarded to Meghan Vankosky, AAFC entomology research scientist and PPMN co-chair. In Saskatchewan, SCIC conducts most sampling and Manitoba’s ag ministry co-ordinates sampling in that province. To estimate population density per square metre in late summer and early fall, surveyors walk fields and note the number of grasshoppers that take flight. The abundance of various species is also noted. Collected data is compiled to create the annual grasshopper risk map, or forecast map. The PPMN also maintains sites where it conducts grasshopper counts through- out the summer to follow the develop- ment of grasshopper populations from nymph to adult. During the growing season, this information is updated weekly at prairiepest.ca . In Alberta, ideal grasshopper condi- tions prevailed from August through ear- ly October 2022. “In general, the further south we travelled, the higher the grass- hopper population densities got,” said Vankosky. “We generally expect that high densities in the fall translates to higher risk going into spring 2023.” The grass- hopper map indicates a hotspot southeast of Lethbridge, but grasshopper density is generally high south of Calgary. In contrast to the south, Vankosky suggested farmers north of Edmonton and into Peace Country be vigilant in 2023, even though grasshopper numbers in the region were low in 2022. Associated with the Prairie treeline, Bruner’s grasshopper appears to be on a unique odd-year cycle and its population is less predictable than other pest grasshopper species. “This every-second-year trend is not always cap- tured in the survey,” said Vankosky. “This could be a year, again, where we do see higher numbers of Bruner’s grasshopper.” She also suggested farmers across the Prairies scout for grasshoppers early and often this spring, especially if weather is dry and warm. “Grasshoppers respond very well to those conditions, and that will contribute to increased risk.” The best time to kill grasshoppers is when they’re young as they are smaller and less mobile, she added. WHEAT STEM SAWFLY Barkley oversees the fall survey of wheat stem sawfly, an insect of special concern to farmers in southern Alberta. The annual two week project is conducted on 100 farms south of Highway 9 through to the U.S. border and from Pincher Creek to the Saskatchewan border. In five fields per county, surveyors calculate the ratio of cut stems to uncut in four one-metre row sections per field. Hotspots with greater than 25 per cent cut stems appear in red on the risk map. “Wheat stem saw- fly really does well in the County of Forty Mile,” said Barkley. The 2022 survey found fewer high-den- sity areas than in 2021, but the insect was found in more fields across a greater area. A single infested field was identified in Knee Hill County north of Highway 9. Though sawfly flourished in the heat of 2021, B racon cephi , the parasitic wasp known to keep its numbers in check, did not. Its population may yet be on the rebound. The wasp overwinters high in the wheat stem, while the sawfly migrates to the crown and can even Indispensable insect counts Prairie surveys calculate threat posed by three top cereal pests Farmers across Alberta are advised to scout for grasshoppers this spring as there is potential for their numbers to surge.