Scout alert: spider mites

July 21, 2023 | Kriss Nelson

The Iowa Soybean Association (ISA) is alerting farmers to be aware of a potential outbreak of two-spotted spider mites. Due to prolonged dry weather, producers are urged to scout for the pest.

Drought increases pest presence

According to Iowa State University Extension, two-spotted spider mites can increase rapidly when temperatures are greater than 85 degrees and humidity is less than 90%.

What to look for

Spider mites can typically be found feeding on the bottom side of crop leaves with feeding beginning at the bottom of the plant.

Initial feeding looks like yellow or white spots, called stippling, on the leaves.

Prolonged feeding will cause infested leaves to turn completely yellow, then brown with the leave eventually dying and falling from the plant.

What to do

ISA Research Agronomist Scott Nelson says producers should be mindful of the pest and aware of insecticide-fungicide interactions.

“Many farmers apply insecticide with their fungicide applications and these can cause spider mite flareups because the insecticides kill beneficial pests,” he says. “I strongly recommend farmers not apply insecticides with their fungicides unless they are using bifenthrin and they know they have an insect problem. Prophylactic applications will drive resistance to pests.”

Find more information about the pest via the Soybean Research and Information Network (SRIN), administered by the North Central Soybean Research Program and supported through your checkoff investment.

Contact Kriss Nelson at knelson@iasoybeans.com.

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