Look for mites on the undersides of leaves using a hand lens, or by tapping leaves over a piece of paper. Webbing is an indication of a very high mite population. For dry bean and soybean, treat when 25 percent of the plants have mites, and yellowing is seen. Use a product like dimethoate. Thrips often can start out on wheat, then move to other crops as the wheat dries down.
Thrips feed by rupturing plant cells and sucking the contents.
Damaged leaves have a silvery appearance, while severe damage leads to cupping, distortion, and death of leaves. As with mites, sampling can be done by tapping a plant over a piece of paper. Thrips rarely are present in high enough numbers to warrant spraying. For soybean and dry bean, treat if a third of plants have thrips and dry leaves are present. Also, look for thrips feeding in blossoms of drybeans, which can cause flowers or pods to abort.