Natural Aphid Control
NATURAL APHID CONTROLAphids, also called plant lice, are small (up to 1/4 inch) soft-bodied insects that infest most garden plants. Some aphids spend their entire lives on one type of plant; others infest different varieties. Most gardeners can readily identify the green aphids, but black, brown, yellow, and gray aphids are also common. There are also winged and wingless varieties of aphids. A few aphid species attack parts of plants other than leaves and shoots. The lettuce root aphid is a soil dweller that attacks lettuce roots during most of its cycle, causing lettuce plants to wilt and occasionally die if populations are high. The lettuce root aphid overwinters as eggs on poplar trees, where it produces leaf galls in spring and summer. The woolly apple aphid infests woody parts of apple roots and limbs, often near pruning wounds, and can cause overall tree decline if roots are infested for several years.
HOST PLANTS: Most aphids are found on the underside of leaves or on stems at the tip. Aphids like the tender new growth found on the actively growing branch ends of roses, flowers, ornamentals, vegetables, and fruit trees. Aphid activity starts as soon as new leaves appear in the spring. Large populations can be found from early spring to early fall depending on the species of aphid and host plant.
SYMPTOMS: The plant damage done by aphids is not necessarily proportionate to the size of the aphid population. Large populations may do very little damage, while a few aphids may severely harm a plant. Aphids cause curling, yellowing, and distortion of leaves and stunting of shoots; they can also produce large quantities of a sticky exudate known as honeydew, which often turns black with the growth of a sooty mold fungus. Some aphid species inject a toxin into plants, which further distorts growth. A few species cause gall formations. In addition to the damage done by the aphids themselves, aphids act as conduits for diseases, which further damages plants. Squashes, cucumbers, pumpkins, melons, beans, potatoes, lettuces, beets, chards, and bok choy are crops that often have aphid-transmitted viruses associated with them. The viruses cause mottling, yellowing, or curling of leaves and stunting of plant growth.
APHID CONTROL: A strong spray of water from a hose will knock many of the aphids off the plant although it will not keep them off it is a good method to start. Killing aphids naturally is not only better for the environment, but it is also a more effective way of killing the insect. Aphids don’t respond well to insecticides, but you can get them under control by taking advantage of their weaknesses and making a few changes in the way you manage your garden.
Aphids have a number of natural enemies, and these insects are much better at controlling aphids than any other method available to gardeners. Pampering and nurturing their natural enemies is an excellent method of organic aphid control. Introduce beneficial bugs like lacewings and ladybugs to your garden as a cheap and organic solution to aphid control. There are also aphid-specific parasites called parasitoids. These species include A. abdominalis, A. aphidmyza, A. colemani, A. ervi, and A. matricariae, Nearby plantings of mint, fennel, dill, yarrow, and dandelions will help attract these insects to your garden.
Pesticides are more likely to kill the predatory insects than the aphids, so the insect population usually increases after spraying. Using natural ways to kill aphids preserves the insect’s natural enemies while creating a hostile environment for aphids.
While predatory insects are bent on destroying aphids, ants in the garden are the aphid’s sworn protectors. Ants feed on the honeydew produced by aphids, so it is in their best interest to defend this precious resource. Getting rid of the ants so that the predatory insects can do their job is an important part of a good aphid control program.