European corn borer numbers up this year
WEST LAFAYETTE, Ind. - Reports of European corn borer damage have increased this year, but a Purdue Extension entomologist says there is little cause for alarm.
European corn borers devastated fields in the 1990s, but the development of a genetically modified hybrid called Bt-corn greatly reduced the pest's numbers. There have been very few reports of European corn borer in recent years, said Christian Krupke.
While there have been more sightings of corn borer damage in non-Bt-corn, he said the reason for that increase is uncertain and probably stems from environmental conditions.
"This is more of a curiosity than anything to be concerned about as levels are still considerably lower than in the past," Krupke said. "There is no evidence that the European corn borer has resistance to the Bt protein."
Favorable weather during adult breeding, overwintering and egg hatching can lead to high populations of corn borers, he said. Heavy snowfalls in Indiana this winter protected the insects from temperature fluctuations.
Growers' seed selection and planting practices also is a likely driver.
"The European corn borer has been out of sight, out of mind for a few years. Farmers might have forgotten about the threat and not purchased Bt protection for this pest," Krupke said. "On the other hand, Bt protection against various pests is now bundled into one, so many farmers using 'traits' will still have it."
The damage seen so far this year has been from the first generation, when moths chew small holes in the stalk and leaves. In July, the moths deposit eggs in the ears of corn. This second generation is the greater concern for farmers, Krupke said.
"After the European corn borer is inside the ear, it's too late," he said. "Anyone who doesn't have Bt-corn should be paying attention to reports about trap catches in case they need to apply an insecticide."
Krupke recommended that growers with non-resistant varieties – especially high-value corn types where first-generation numbers were high - scout their fields weekly for egg masses. More information about identifying and sampling for European corn borer can be found at https://extension.entm.purdue.edu/fieldcropsipm/insects/euro-cornborer.php
Writer: Lisa Schluttenhofer, 765-496-2384, firstname.lastname@example.org
Source: Christian Krupke, 765-494-4912, email@example.com