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Spider Mites Infesting Michigan Soybeans

August 21, 2017
This agronomic image shows spider mite damage to soybean leaves.

The University of Michigan Extension reports spider mites are beginning to infest soybean fields in different areas of the state. Last week was the first report of spider mites in Kalamazoo-area fields.

Though much of Michigan has been wet this summer, there have been areas throughout southwest and south central Michigan that have been hot and dry, which are conditions conducive to a spider mite presence.

Spider mite scouting tips:

  • Pull up some of the affected plants, shake them over a white piece of paper and wait for about 30 seconds.
  • If spider mites are present, you will see what looks like small grains of sand start to move on the paper.

The Michigan State University Extension defines the following thresholds (based on percent yellowing) for spider mite treatment:

  • Pre-bloom = 40%
  • Bloom R1 to pod fill R5 = 15%
  • R5 to early maturity R7 = 25%
  • After R7 = do not spray, as damage at this point has little impact on yield

If weather remains hot and dry, spider mite populations are more likely to thrive. Once spider mite levels reach the economic threshold, we recommend applying Agri-Mek® SC insecticide for extended residual control.

Additionally, Agri-Mek SC can be easily tank mixed with Endigo® ZC insecticide for control of soybean aphids, Japanese beetles and stinkbugs.

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