Aphids are found throughout the United States.

These small, soft-bodied insects may be pale green, pink, black, or yellow, depending on the species.

Some stages of the life cycle are winged, others wingless. Aphids feed on a wide variety of plants, including most edible and ornamental plants. Clustering on tips of new growth and leaf undersides, they suck plant juices causing leaves to become distorted and yellow.

These reddish-brown nocturnal creatures feed primarily on decaying organic matter or other insects, hiding in dark, damp places during the day. They are found throughout the United States, and when their populations are high, they may cause damage in the garden by feeding on a variety of plants such as lettuce, corn, celery, tender young seedlings, and blossoms and ripening fruits.

Japanese beetles are primarily a pest in the eastern U.S., though they turn up west of the Rockies from time to time. Their appetite for a wide variety of plants makes them especially troublesome. Adults feed on just about every kind of ornamental and edible crop, sometimes in disturbingly large crowds. They chew leaf tissue from between the veins, leaving a lacy skeleton. Prior to pupating, the 1-inch-long, white, c-shaped grubs live in the soil and feed on the roots of many plants. Grubs are often a problem in lawns.

Different species of scale insects attack various kinds of fruits and ornamental plants in all parts of the country. They attach to branches, twigs, and the undersides of leaves, appearing as small bumps. Some are flattened and brown, while cottony cushion scale is thick, white, and covered with a waxy or woolly substance.

Leaves on infested plants turn yellow and the overall vigor of the plant declines. Severely infested plants may die within several seasons.

There are numerous kinds of mites, also known as spider mites, and many feed on plants. They congregate in dense colonies in webs on the undersides of leaves. Symptoms of their feeding show up as silvering or a stippled effect on the leaf top, but the precise symptom varies with the plant. Turn over affected leaves and you're likely to find spider mite webbing; if you rub the leaf it will feel gritty. Mites feed on many kinds of plants, edible and ornamental. Houseplants are a favorite target.