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Spider Mites in Soybeans

Spider Mites occur on soybean in hot, dry years.  Populations can reach economic damage very quickly in fields, and so field should be closely scouted.  Mites are very small and difficult to see clearly with the unassisted eye.  A quick test to determine if spider mites are present is to take a white piece of paper, place it under the soybean leaves, and jerkily shake the plant to dislodge the mites.  Tiny dark specks will move across the paper if spider mites are present.  

Initial spider mite feeding will cause yellow spotting on the leaves (leaf stippling).  As feeding continues, leaves will become yellow, bronze or brown and eventually fall away from the plant. Field edges and droughty areas of the field are most likely places for initial spider mite activity. Scout from full pod through beginning pod development.  When the crop reaches full seed (R6), no treatment is recommended.

Insecticide treatment is advised when heavy stippling on lower leaves with some stippling progressing into middle canopy.  If spider mites are the main pest problem, the only pyrethroid that will control mites is bifenthrin active ingredient (Tundra, Sniper, Brigade, Fanfare, Bifenture, etc.) in soybeans. Other pyrethroids which are used for soybean aphid control, such as lambda-cyhalothrin (Warrior, Silencer, etc.), will cause spider mites to flare up and increase their reproductive rate. Two active ingredients of organophosphate (OP) insecticides for control of spider mites include chlorpyrifos and dimethoate.

 

Resources: Spider mites, ND Field Crop Insect Management Guide (E-1143)

"Soybean Aphids and Spider Mites Update", Crop and Pest Report 8/22/13, J. Knodel

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