Catalpa hornworm, up to 3 inches long, has a broad black stripe down the back with a sulfur yellow stripe along each side. There is a distinctive spike-like horn at the end of the body. There are two generations each year; each feeds for about 3 weeks. Caterpillars of the first generation are active in May, the second generation feeds in late summer. When abundant, these caterpillars can completely defoliate trees.

Aphids are soft-bodied insects that use their piercing sucking mouthparts to feed on plant sap. They usually occur in colonies on the undersides of tender terminal growth in the spring. Heavily-infested leaves can wilt or turn yellow and senesce prematurely because of excessive sap removal. While the plant may look bad, aphid feeding generally will not seriously harm healthy, established trees. Some plants are very sensitive to feeding by certain aphid species. Saliva injected into plants by these aphids may cause leaves to pucker or to become severely distorted, even if only a few aphids are present. Also, aphid feeding on flower buds and fruit can cause malformed flowers or fruit.

Aphids produce large amounts of a sugary liquid waste called "honeydew". The honeydew that drops from these insects can spot the windows and finish of cars parked under infested trees. A fungus called sooty mold can grow on honeydew deposits that accumulate on leaves and branches, turning them black. The appearance of sooty mold on plants may be the first time that an aphid infestation is noticed. The drops can attract other insects such as ants, flies, and wasps that will feed on the sticky deposits. For more information, see Entfact 103.

Mealybugs are small, elongate, segmented insects that usually have waxy filaments coming off of their grayish bodies. They congregate on plants in white cottony masses. Heavy infestations can cause premature leaf drop and stunt growth or cause twig dieback. Mealybugs produce large amounts of sticky honeydew (liquid waste) that supports the growth of sooty mold. Healthy vigorous plants can tolerate moderate mealybug infestations which may allow natural enemies of the insects to provide some control.

Comstock mealybugs are small, oval, waxy pests that feed on the sap of plants. Adult females are 3/16 inch long; the body is a brownish color but is coated with a white wax. They produce honeydew as fecal material which can also encourage the growth of black sooty mold on the plant. There are two generations per year, with overwintering eggs hatching in the spring. Spring nymphs feed and mature by July. They mate and then produce another generation that matures by September.