Aphids
Cabbage Aphids, Green Peach Aphid, Melon Aphid, Potato Aphid
Description
Cabbage Aphid
Adult and nymph: Green-gray with a white waxy coating and short cornicles (two “tail-pipes” on the tail end of the abdomen). Adults may be winged or wingless. Cabbage aphids form dense colonies on undersides of leaves of broccoli, Brussels sprouts, cabbage, cauliflower, kale, and other related cole crops. Aphids prefer to feed on young leaves and flowering structures; they can occur deep inside the heads of Brussels sprouts and cabbage.
Green Peach Aphid
Adult: With soft, pear-shaped bodies and red eyes, adults have tailpipe-like appendages called cornicles on the rear of the body. Wingless adults are yellowish or greenish. The winged adult has a yellow-green abdomen, with a large dark patch on its back. It has a black head and thorax and is the same size as the wingless form. The oviparous (egg-laying) form is pinkish.
Egg: Eggs are initially yellow or green, eggs become shiny-black as they mature. Eggs measure about 0.5 mm long and 0.25 mm wide. Eggs are usually deposited near buds of Prunus spp. trees.
Nymph: Though similar in shape and color to the wingless adult, nymphs are smaller. Nymphs that develop into winged adults may be pinkish.
Melon Aphid
Adult: Soft-bodied, pear-shaped with dark cornicles, melon aphid adults are smaller and have shorter appendages than the green peach aphid. Winged adults are about 1.25 mm long with yellow to dark green bodies. They have a black head and thorax. Wingless adults are about 1 to 1.5 mm long with yellow to dark green bodies.
Egg: Eggs are yellow when first deposited, and turn shiny black when mature.
Nymph: Nymphs resemble adults but are smaller in size, about 0.5 to 1.0 mm long.
Potato Aphid
Adult: Potato aphids are larger than the green peach and melon aphids, 2-4 mm long with pink or green bodies.
Egg: They are similar to green peach and melon aphid eggs.
Nymph: Nymphs are a similar color and shape as adults, but smaller.
Life History
Cabbage Aphid-As aphid densities increase or plant conditions deteriorate, winged adults are produced, and they migrate to alternate hosts, including vegetables and weeds, during the summer. Winged adults colonize plants by depositing live young on one plant and then flying to a nearby host plant. Aphids reproduce asexually (parthenogenesis) during the spring and summer and sexually in the late summer and fall. Many overlapping generations occur each year.
Green Peach Aphid, Melon Aphid, Potato Aphid-The green peach aphid overwinters as eggs at the base of buds in peach/nectarine trees, the melon aphid overwinters on a variety of woody plants and weeds, and the potato aphid overwinters principally on wild and cultivated rose plants and is generally more common in vegetable crops in the spring and fall. Green peach aphid and melon aphid populations peak on vegetable crops during July and early August.
Bean Aphid, Lettuce Aphid, Lettuce Root Aphid, Turnip Aphid
Description
Adult: They have a soft, pear-shaped body with tailpipe-like appendages called cornicles on the rear of the body. Adults range in color from yellow, green, orange, and pink depending on the species, time of year, and food source. Lettuce root aphid adults have a white powdery wax covering their bodies, short antennae, and their cornicles are undeveloped compared to other aphids found on lettuce. They feed in clusters on lettuce roots.
Egg: Initially yellow or green, eggs become shiny black as they mature.
Nymph: Similar in shape and color to the wingless adult, nymphs are smaller.
Life History
Lettuce Aphid, Lettuce Root Aphid-Most vegetable aphid species have similar life cycles. Each of the following aphids overwinter as eggs. Lettuce aphid overwinters on Ribes spp. such as blackcurrant and gooseberry bushes, and lettuce root aphid overwinters on the bark of Lombardy poplar. Eggs hatch as all females when leaf buds expand in spring. Adults reproduce asexually, give live birth, and have two to 16 generations during the growing season. Aphids move from overwintering hosts to vegetable crops and/or weeds for the summer. Winged aphids develop when food quality declines, crowding occurs, or when they are seeking new plant hosts. In late summer to fall, aphids lay eggs for overwintering.
Bean Aphid, Turnip Aphid-Little is known about the overwintering behavior of turnip aphid. Because its appearance and habits are so similar to cabbage aphid, the two species have often not been distinguished. Bean aphid overwinters on Euonymus sp. (burning bush) and Viburnum sp. (snowball bush).
Aphid Damage
Aphids may contaminate harvested plant parts, leaving them unmarketable. Their feeding may cause stunted, yellowed, distorted, and/or curled leaves and loss of plant vigor. Aphids secrete a sticky, clear substance called honeydew, on which sooty mold fungi may grow. Lettuce root aphids feed on roots of host plants. Under heavy attack, plants will wilt during warm temperatures. Developing lettuce heads fail to develop properly, remaining soft and reducing yield. Plants may collapse and die when aphid populations are extremely high over a long period. Masses of white, woolly material along with aphids can be present on the roots. Individual rootlets turn brown and die.
Aphids also vector viruses. The most common aphid vectored diseases of concern in Utah are alfalfa mosaic virus (tomato, pepper, potato, pea, bean), potato virus Y (potato), and watermelon mosaic virus (cucurbits). Occasionally, other diseases carried by aphids are observed.
Aphid Management
Cultural
- Avoid excess fertilization. Aphid densities tend to be higher on plants that have succulent, vigorous growth.
- Use mulches or row covers. Reflective mulches and row covers can help reduce aphid populations on vegetables by interfering with the ability of winged aphids to find plants.
- Remove and destroy plant debris. Discing fields immediately after harvest will destroy alternate host plants and reduce available aphid and virus sources.
Chemical
Many aphid species in other parts of the world have developed resistance to multiple insecticide groups, including some synthetic pyrethroids, carbamates, and organophosphates. In Utah, use these insecticides sparingly; instead, choose products that are less damaging to natural enemies of aphids and non target insects.
Biological
Natural enemies such as lady beetles, lacewings, syrphid flies, and parasitic wasps play a major role in suppressing aphids.