The mysterious orange maggots that riddled soybean stems and robbed yield in parts of Iowa, Minnesota, Nebraska and South Dakota last summer now have known adult relatives.
Entomologists were able to capture some soybean gall midge adults in the field and confirm their identity by rearing a few larvae to adulthood in a laboratory environment. Prior to that, scientists guessed they were dealing with a midge but had no idea what the adults looked like. University of Nebraska entomologist Justin McMechan says this will be helpful in monitoring emergence next spring in problem fields.
The adults that hatched were sent to Raymond Gagne, a collaborator in the USDA ARS Systematic Entomology Laboratory, and Junichi Yukawa, emeritus professor of Kyushu University, Japan, leading authorities in midge identification.
The winged adult is approximately 1/4-inch in length with an orange abdomen and legs with distinctive black and white bands. They were identified as part of the Resseliella genus, of which there are 55 species worldwide, 15 of which have been identified in the United States. However, none of these species are known to occur on soybeans, and DNA and morphological comparisons indicate it is likely a new species, McMechan says.
It’s assumed soybean gall midge overwinters in fields or on field edges. “We’re still learning about them. I know farmers are anxious for management tactics, but what I can say is we’re making progress, but this is an all-new pest,” he says.
McMechan says yield-loss estimates on a small sample of plants from a heavily damaged field indicate nearly complete yield loss from the field edge up to 100 feet, with about a 20% yield loss 200 and 400 feet from the field edge. Farmers should contact university entomologists for opportunities to cooperate in trapping and monitoring programs in 2019.
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