2012 Too Dry for Many Pests
NEW PROBLEM PESTS
Krupke reported that most other crop insect pests also failed to develop. Adult corn rootworms did more damage than many years, but didn't reach the problem level of 10 years ago, he added.
One pest that was a problem was the bean leaf beetle that invaded late in the season. The pod-feeding adult caused enough damage to justify treatment. However, by the time the damage was recognized, it was too late to take action—for this year.
"We've had high populations for two years in a row, so producers need to be scouting earlier, perhaps mid-August, for population levels and considering control," said Krupke.
Most of the insect pest populations in Missouri were also depressed. Spider mites and redheaded flea beetles were the exceptions, according to Wayne Bailey, Extension entomologist, University of Missouri. "Spider mites were severe in soybeans until it got too dry even for them," he said. "The flea beetle turned to corn in response to the drought. They would stand and feed on the liquid coming out of the silks, and then as it dried up, clip another half an inch of silk off to restart the liquid."
Wireworms were a problem early in the season before moving deep into the soil. Bailey expects them to return again next year as part of a five-year cycle. Although stinkbugs were a problem in corn (brown) and soybeans (green), they weren't as much of a problem as Japanese beetles. The pest is spreading from the East into the South and West and caused damage in soybeans and corn, although Bailey noted there was a lot of damage in some fields and not others.
"Early insect pressure included secondary pests like corn maggots and even seed corn beetles in some fields," he said. "Normally we get control from seed treatments, but this year it was so dry that the chemicals didn't move off the seed."
Like Krupke, Bailey noted problems with the bean leaf beetle. In Missouri, they were more severe on untreated fields. However, very high numbers early season feeding on vegetation and a later season second generation feeding on pods would have affected yields if the drought had not already taken its toll. The soybean podworm, also known as the corn earworm, can cause 100 percent yield losses in some parts of the state.
TREATING VS. BENEFICIALS
He also pointed to a growing problem with the spotted cucumber beetle or southern corn rootworm (CRW). Showing up in soybean fields, it can defoliate up to 50 percent of the plants and then feed on the flowers, taking out 100 percent of the flowers. Seed treatments don't stop it, and with fewer over the top insecticide treatments, the pest is flourishing. Ironically, the use of insecticides may be part of the problem, especially with the soybean podworm.