Green beans are normally easy to grow in summer vegetable gardens but they can attract a number of insect pests. If your green beans develop yellow insects, pick the insects off by hand and treat the plants with insecticidal soap as soon as possible.
This insect is 1/8-inch long and yellow-green with six spots behind its head. Although potato leafhoppers can fly, they usually jump when you disturb them. Adults and nymphs both cause damage by sucking sap from the plant, usually from the undersides of leaves, which become crinkled. Plants become stunted and harvests will be small. Sevin is an insecticide used to control this pest.
This worm is the larval stage of the click beetle. It is brownish-yellow and up to 1-1/2-inches long. Worms eat green bean seeds, causing poor germination rates and leggy seedlings. Avoid planting seeds in cool, damp soil, which provides an attractive environment for this pest. The insecticide difonate is used to control this pest.
Bean Leaf Beetle
This 1/4-inch-long insect is yellow to reddish-brown and can have black spots on its wings. Look for a distinguishing black triangle behind the head. Bean leaf beetles eat green bean leaves, leaving small, round holes. An attack causes loss of vigor and size in the green bean plants, as well as a reduced harvest. The beetles also eat forming bean pods. The pesticides "Capture" and "Lannate" are effective controls.