Corn earworm on the rise in Ontario crops

Oct 10, 2018

Levels are higher than expected this fall

Staff Writer

Farms.com

Corn earworm (CEW) is appearing in Ontario corn fields at rates higher than expected this fall, an OMAFRA field crop news report said Thursday.

Fields planted later in the season face an increased risk of developing CEW because the moths travel from the U.S. in late summer and prefer to lay their eggs on fresh silks. Extended and warmer fall weather, along with strong storm fronts, could cause the moths to travel from southern states more frequently.

"The moths come in ... depending on when the wind brings them up because they're not flying on their own strength," said Johanna Lindeboom, CCA, sales agronomist for Clark Agri Service, to Farms.com today. “They could be coming in in August or September.”

Typically, CEW tends to be a greater concern in sweet corn than in grain corn, Lindeboom added.

“This year, (however,) we haven't seen a whole lot in sweet corn, but we have seen some in grain corn."

Western bean cutworm (WBC) levels were lower in corn crops this year compared to other years because of early planting, but OMAFRA reps are concerned that producers could mistake CEW for WBC.

Farmers and scouts can overlook CEW and WBC because the larvae can penetrate the corn through the silk at the tip of the ear. While damage from CEW and WBC can appear to be similar, only WBC can leave holes in the husks.

The key to differentiating between WBC and CEW comes down to larvae. Both WBC and CEW larvae can be brown or beige, though CEW larvae can be green, yellow or brown and have stripes. WBC larvae typically lose their stripes when they are “in the last instar stages of larvae,” the report states.

The heads of the larvae also indicate whether an infestation is WBC or CEW. The heads of CEW larvae are commonly light brown with veins, and they do not have “two broad bands behind their heads that WBC have,” the report explains.

An additional difference between the larvae is that CEW larvae have spines, or hairs, that stem from warts along the sides of their bodies. WBC larvae have neither spines nor warts.

The industry is also developing crops that are resistant to CEW, said Lindeboom.

"Most of the genetic companies are looking at next-level traits for (CEW) to combat it, but it's definitely something ... I have seen this fall," she said.

If you find CEW in your fields, email Tracey Baute at tracey.baute@ontario.ca.

alffoto/iStock/Getty Images Plus photo

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