We've been getting calls about spider mites in soybeans, not surprising given our high temps and the dry conditions in some locations. As temps get into the 90's, spider mite reproduction and development rates increase significantly. Drought also exacerbates spider mite populations, and when drought conditions are relieved by rain, spider mite populations may not necessarily decrease. Consequently, even after drought conditions pass, best to continue scouting for spider mites damage.
Spider mites are tiny and only large females are visible to the naked eye (unless you've got really good eyesight!). The best way to see spider mites is to shake a plant over a piece of white paper - any moving pieces of dirt are likely spider mites... So to scout for something that small, it's best to look for damage. Spider mite damage will first appear as small yellow spots (stippling) on lower leaves. There is currently no solid treatment threshold in soybeans, but If stippling reaches mid-canopy leaves, a treatment is likely necessary. Pyrethroids may flare spider mite populations, spreading mites and increasing their populations.
A good source for information on spider mite biology, scouting and thresholds was prepared last year by Bruce Potter and Ken Ostlie and is available at: