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Modernizing management of true armyworm in Ontario

Principal Investigators: Jocelyn Smith, Art Schaafsma and David Hooker

Research Institution: University of Guelph

Timeline: April 2021 – March 2024  


  • Improve true armyworm monitoring and scouting alerts in Ontario through increased pheromone trapping in various regions to detect the timing and abundance of moth migration.
  • Determine levels of biological control of true armyworm in Ontario and identify key parasitoid, predator, and entomopathogen species.
  • Revise economic thresholds for true armyworm larvae in cereals in relation to crop growth stage.
  • Determine the susceptibility of true armyworm in Ontario to Cry1Ab, Cry1A.105, Cry2Ab2, and Vip3A Bt corn proteins, including various larval instars (e.g., 1st, 3rd, 5th).
  • Determine the susceptibility of true armyworm in Ontario to currently registered insecticides, including relevant larval instars (e.g., 3rd and 5th).
  • Economic analysis of the impact of TAW and integrated pest management of TAW in cereals.


  • The development of a comprehensive integrated pest management plan for TAW in Ontario (incorporating knowledge of biological control services, the economic impact of TAW, and the efficacy of control tactics) will benefit Ontario cereal and corn producers by minimizing costly unnecessary pesticide use, reducing negative environmental impacts and providing ongoing sustainable suppression.
  • The delivery of improved monitoring of TAW to Ontario cereal and corn producers, including timely and coordinated information of TAW infestations that provide earlier warnings and better prediction of economic infestations.
  • Measurement of baseline susceptibility of TAW to Bt proteins and insecticides and development of expertise in rearing and insect resistance management bioassay methodology with TAW will provide the infrastructure and knowledge to protect the longevity of transgenic technology and insecticides in Ontario.
  • Optimizing IPM strategies for TAW management will encourage Ontario producers to include cereals such as winter wheat in their crop rotation, enhancing crop rotation diversity and agroecosystem resiliency in an economical manner.
  • Training highly qualified personnel in integrated pest management and agronomy, such as the MSc student planned in this project, provides valuable human resources within the Ontario agricultural industry.

Scientific Summary:

True armyworm (TAW), Mythimna unipuncta Haworth (Lepidoptera: Noctuidae) causes economic damage to winter wheat, spring wheat, and barley in Ontario during outbreaks. Economic injury to corn may also occur in outbreak years when TAW migrate from cereal fields into corn fields. Over the last 12 years, Ontario experienced TAW outbreaks in 2008, 2012, and 2020, which primarily affected winter wheat crops. As TAW has historically been a sporadic pest in Ontario, much of our current management approach is based on research that was conducted >50 years ago. With advances in cereal crop management, increased adoption of cover crops in grain production, and the potential impacts of climate change on TAW populations and their natural enemies, there is a need and opportunity to develop a modern, more proactive and sustainable approach to TAW management in Ontario. Currently, cereal producers rely on notifications of TAW populations in the spring from neighbouring US states as routine monitoring is not conducted in Ontario. Widespread scouting efforts are reactive, being initiated in response to discoveries of high numbers of larvae in a limited region, and control decisions are based on outdated economic thresholds and biological control knowledge (Guppy 1967). Establishing modern thresholds based on crop stage and a new biological control assessment could provide more precise spray timing and reduce unnecessary insecticide applications when the crop is advanced enough that yield loss is no longer a concern. Furthermore, a limited number of insecticides are registered and the susceptibility of TAW to these active ingredients is unknown. As fewer insecticide registrations are anticipated in the future, the impact of biological control agents and their conservation will become increasingly important. Implementation of biological control of TAW has the potential to reduce insecticide use, minimizing risks to non-target beneficial insects and lowering production costs for cereal producers.

External Funding Partners:

The project was funded in part by the Ontario Agri-Food Innovation Alliance, a collaboration between the government of Ontario and the University of Guelph.