Aphids

Green Peach Aphid

The green peach aphid is commonly found on eggplants early in the season. Generally its color is pale green, although at times individuals may be present that are pinkish. During cool weather, individuals are usually more deeply pigmented. Both winged and wingless forms of the green peach aphid have prominent cornicles on the abdomen that are markedly swollen and clublike in appearance. The frontal tubercles at the base of the antennae are very prominent and are convergent. Winged forms of the green peach aphid have a distinct dark patch near the tip of the abdomen; wingless forms lack this dark patch.

Cotton (Melon) Aphid

In mid-summer, cotton or melon aphid is more prevalent. This aphid is highly variable in body size and color, and adults may be winged or wingless. Nymphs and adults of wingless cotton aphids vary in color from yellow to green to nearly black. The darker forms tend to be substantially larger. Nymphs that are developing into winged adults look very different from the nymphs developing into wingless adults: they bear small welts or protuberances on their bodies and may be covered with a coat of dusty-appearing whitish wax. Their body color is often greenish blue, or amber and blue.

The different forms of the cotton aphid differ in their ability to cause population outbreaks and plant damage so it is important to be aware not only of the number of aphids present, but also of their color form. The small yellow aphids develop slowly from newborn nymph to adult and do not produce many offspring; thus, their populations rarely increase rapidly. The larger, darker aphids (green and black) are quite different; they develop more rapidly, produce many more offspring in a rapid burst, and can generate rapid population growth rates.

The primary damage caused by aphids to eggplants is the production of sticky honeydew and subsequent growth of black sooty mold on the honeydew. They can also stunt plants by feeding on them early in the season before bloom. There do not appear to be any serious virus problems associated with aphid infestations.

Conserve natural enemies by avoiding early season use of disruptive insecticides. Treatment is not usually needed for eggplant crops planted in spring but may required for summer plantings.

Many parasites and predators attack aphids. Among the more common predators are lady beetles and their larvae, lacewing larvae, and syrphid fly larvae. Populations of green peach aphids are reduced in winter by a parasitic fungus, Entomophthora aphidis. Many materials available for aphid control are highly disruptive of natural enemy populations.

Winged aphids are repelled by silver- or aluminum-colored mulches. If there is a probability of severe virus pressure, place reflective polyethylene mulches on planting beds before seeding or transplanting to significantly reduce rate of colonization by winged aphids and delay the buildup of damaging numbers of aphids by 4- to 6-weeks. While this approach is mainly effective in delaying or reducing the incidence of virus diseases transmitted by winged aphids and whiteflies, reflective mulches can also delay the buildup of wingless aphids that arise as a result of colonization by winged individuals. The mulches lose their effectiveness when more than 60% of the surface is covered by foliage or if the mulch becomes fouled with dust or soil. Therefore, they are effective only for the first few weeks after transplanting.

Cultural and biological controls and sprays of insecticidal soap, horticultural oils (including both plant and petroleum oils), or pyrethrinare acceptable for use on organically certified produce.

Green peach aphids may move into early-season eggplant transplants but rarely require treatment because they are often kept under control at this time by many natural enemies, including lady beetles, lacewings, syrphids, and parasites. Monitor populations, especially in summer, and apply a treatment if populations are continuing to increase. No monitoring protocol or thresholds have been established. Follow aphid populations by examining underside of leaves. Note any increase in population or the lack of parasitized mummies (expanded brown corpses). Monitoring is especially critical during fruit development because honeydew will spot the fruits and require washing to remove.