Corn School: Changing weather patterns create pest challenges

Western bean cutworm damage. Photo source: OMAFRA

Changing weather patterns played havoc with corn planting and harvest in 2019 and they also affected insect cycles and how pests impacted the crop.

Ontario Ministry of Agriculture, Food and Rural Affairs entomologist Tracey Baute notes that the cold, wet spring had a big impact on western bean cutworm (WBC). A significant reduction in early-season Growing Degree Days slowed the pest to the point that some areas of the province such as Essex County actually missed the cutworm. The pest, however, did have a significant impact in central and eastern parts of the province.

In these areas, peak WBC moth flight was delayed at least two weeks. But those moths were still looking for corn and may have laid their eggs right on the husk of the ear — a place growers don’t typically look for eggs or larvae.

On this episode of the RealAgriculture Corn School, Baute also takes a look at another pest growers will have to be on the lookout for in the years ahead. Corn earworm (CEW) damage was much higher in 2019 and will likely become the “next corn pest,” she says.

Earworm is generally considered a late-season pest, but that’s changing, says Baute. This year she notes that growers in Quebec and New York saw CEW moth flights as early as May and June. The pest typically overwinters in the southern U.S., especially in the corn and cotton growing regions, but with changing weather patterns and milder winters, it’s moving north and overwintering closer to Ontario. (Story continues after the video.)

When the pest does arrive in higher numbers in Canadian corn growing areas, controlling it will prove challenging. Baute notes many of the Bt technologies don’t work on CEW and there is also growing resistance to other Bt events due to extensive exposure to the technology in the southern U.S. Insecticides are not a strong control option.

Baute says she and her OMAFRA colleagues plan to collaborate with Great Lakes and maritime pest monitoring networks to gain a better understanding of earworm flight patterns. The moths lay eggs directly on the corn silk, making scouting difficult. But if researchers can identify when moths are flying and combine this information with silking dates, they can determine possible management strategies, adds Baute.

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