Two-spotted spider mites (TSSM) are an occasional pest of soybeans and corn in Kentucky.

They are present every year, but only important during hot, dry periods. Unfortunately, this is the type of weather we currently have and have had for several months.

Additionally, states to the north of us, including Nebraska and Iowa, are already experiencing some problems.

I have not received information about spider mites on Kentucky field crops but have seen some large populations in fruit trees (different mite but same circumstances). I, therefore, think it wise for those with field crops interest to keep an eye peeled for this pest.

TSSM are greenish-white with two dark spots on the back. Adults are about the size of salt grains. Juvenile TSSM have six legs, but adults have eight legs. Other species of spider mites also attack field crops.

Spider mites become active early in the spring and remain active throughout the summer. They live in thinly webbed colonies on the underside of leaves. Occasionally, you will see web strands between leaves. Hot, dry weather allows rapid population growth with each generation taking about five to seven days to complete.

Infestations tend to start on field margins near broadleaf weeds and/or the side from which the wind is blowing, as they may drift on a breeze. They may then spread out in ever enlarging spots if the weather allows.

In corn, damage presents as yellow stippling on the upper surface of the leaves. Heavy and/or prolonged infestations may cause premature drying resulting in loss of tissue, stalk breakage and kernel shrinkage.

In soybeans, injury could resemble herbicide damage, foliar disease or nutrient deficiency. Feeding results in tiny yellow spots or stipples which may turn orange.

Multiple damaged spots may merge in to larger areas of damage. With severe damage, leaves may turn brown and eventually fall off. Spider mites reduce yields by causing pod shattering, wrinkled seed and early maturity.