Potato aphids are soft-bodied insects that suck the fluid out of leaves, stems and other parts of plants. Tomato and potato plants are the plants most frequently attacked by potato aphids. Aphids are generally found in large groups. Unfortunately, potato aphids are usually found after they have injured the plants. There are many ways to control and treat aphids, both organically and chemically. Potato aphids also can be controlled by using other insects that feed on the aphids.
Adult potato aphids are one of the largest-bodied aphids with a body span of about 0.12 to 0.16 inches in length. The adults can have wings or be wingless. Potato aphids suck the fluids out of the plants. They vary in color depending upon the sex of the insect. Potato aphids move slowly from tomato plant to tomato plant, once a plant is too damaged to provide them with nourishment. The population of the potato aphid increases during spring and fall.
Breeding and Reproduction
Potato aphids reproduce and in the winter on rose bushes, not tomato or potato plants. They produce rapidly; during the spring they give birth to live young, in the fall they produce eggs that live through the winter and hatch in the spring. Female potato aphids can give birth to 12 aphids a day. The female aphids do not need to mate to produce live young or eggs. Young aphids are called nymphs. The young aphids molt four times until adulthood. During warm weather, the newborn can grow into an adult ready to reproduce in seven to eight days. Each one can produce hundreds of young, most of them female.
Damaging Affects on Plants
Potato aphids can destroy a tomato plant in a short time. If potato aphids are found early, you can prevent total destruction of the plant. A small number of potato aphids usually do not damage a plant and you will only notice honeydew, which is a sugary sap on the leaves or stems of the tomato plant. Large infestations of aphids can cause yellowing, curling and falling of leaves and flowers. The honeydew sap they leave on the tomato plant can cause black mold, called sooty mold, to form on the plant. Some species of potato aphids prefer blossoms, which, once the blossoms are damaged, will cause a reduction in fruiting. If young tomato plants are badly infested, the plants will begin to turn brown and die; more mature tomato plants can usually survive but become stressed and do not produce fruit.
Attracting natural enemies can help prevent potato aphids. Aphid enemies include ladybird beetles, aphidiid wasps, lace wing larvae and syrphid fly larvae. If not badly infested, start by spraying tomato plants forcefully with water. Most potato aphids fall off the tomato plant and end up damaging their mouth parts so they can no longer feed. Kaolin Clay mixed with water can be used to rinse off the tomato plants. Kaolin clay is found in most hardware and garden stores and works by leaving a clay residue in form of a white powder on the tomato plant so the aphids no longer recognize the plant tissue. Spraying tomato plants with canola or garlic oil mixed with water prevent the aphids from laying eggs. Do not use this oil mixture during extremely hot days as it can cause your tomato plant to be scalded by the sun.
Insecticidal soaps or neem oil are a widely used spray for potato aphids. Spray the underside of the leaves, as this is where most of the aphids will be. These sprays do not leave a residue that can hurt beneficial insects. However, do not use these sprays when temperatures are above 90 degrees F as they may damage the tomato plant when used in high temperatures. Pesticides can be used to destroy potato aphids but may also kill beneficial insects as well. Potato aphids have the lowest insecticide resistance of all the types of aphids.