Results from the 2024 Ontario corn rootworm (CRW) trap sites monitored through the Adult Corn Rootworm (CRW) Trap Monitoring Network have been summarized in the infographic below.
Thank you to all the trap participants for monitoring their traps this year. These sites are helping us to identify fields and counties with potential resistant corn rootworm populations and understand the rootworm risk for 2025 in continuous corn fields. A big thanks to Dan Bihari, Senior GIS Specialist, OMAFA for developing and maintaining the trap network site and to our sponsors including Grain Farmers of Ontario (GFO), Agricultural Biotechnology Stewardship Technical Committee (ABSTC) and OMAFA for funding trap supplies.
There were 54 trap sites monitored in Ontario this year. CRW adult activity peaked in different weeks in August, depending on the region (see graph on page 1 of infographic). Northern corn rootworm populations were extremely low this year. Western corn rootworm populations were similar to 2023 and 60% lower than in 2022, though 10 of the trap sites still reached or surpassed the CRW trap threshold of 2 beetles/trap/day this year (see graph on page 2). These sites should be rotated out of corn in 2025 to knock back resistant populations and help to maintain what durability we have left in Bt-RW hybrids. In addition, growers at these trap sites are encouraged to consider implementing additional management tools like biocontrol nematodes to help reduce rootworm populations over time and reduce the risk of resistance spread. Counties most at risk of experiencing corn rootworm issues next year including unexpected injury in Bt-RW hybrids include: Chatham-Kent, Perth and Huron (High – 2 – 4.9 beetles/trap/day); Middlesex, Oxford and Waterloo (Very High – 5 – 9.9 beetles/trap/day); and Perth and Wellington (Extreme – >10 beetles/trap/day). These are the same counties and levels as were at high risk in 2023.
Continuous corn production that has relied heavily on repeated use of Bt-RW hybrids are risking losing valuable management tools to resistance. Turning to hybrids containing RNAi traits in fields with Bt resistant populations will drive resistance to RNAi more quickly as it becomes the only mode of action to provide control. A more sustainable corn rootworm management practice is to rotate fields out of corn for one year after three years of continuous corn to knock back rootworm populations. This results in lower risk of rootworm the following one to two years, where other management tools can be used if needed. More information on sustainable rootworm management can be found at: https://manageresistancenow.ca/insects-bt-corn/managing-corn-rootworm-resistance-to-bt-corn-in-continuous-corn-fields/
A more details 2024 report for all trap sites across North America will be made available later this year at: https://cornrootworm.extension.iastate.edu/adult-trapping-network
Click here for a downloadable pdf version with Alt Text of this infographic.
Trap supplies will be made available to anyone who is interested in trapping at sites in 2025. Reach out to Tracey Baute to be added to the trap participant list.