Aphids

By organic_gardener

Aphids are small insects with soft bodies and long, slim mouth parts which are used to pierce leaves, stems, and other tender parts of plants to feed on plant fluids. Nearly all plant species are occasionally eaten by one or more type of aphid. Distinguishing aphid species can be difficult, but isn't typically necessary when trying to control them.

Aphids' color varies depending on species and the primary plants on which they feed. They can be black, green, brown, yellow, or red. Some species of aphid secret a waxy gray or white substance over the body, which makes them appear woolly or waxy. All aphids are pear-shaped, small insects with antennae and long legs. Many species have a unique pair of structures called comicles, which are tube-like projections extending from the back end of the body. These comicles make aphids unique among all other insects.

Usually aphids are wingless in adulthood, but wings do appear among different species, especially during the autumn and spring months when populations increase. Wings provide individual aphids with the ability to migrate to other plants as their food source is exhausted.

Aphids occasionally will feed alone, but mostly gather in large groups on stems or leaves. Aphids don't typically move quickly when disturbed, unlike plant bugs, leafhoppers, and other insects commonly confused with them. (Flint)

Aphid Diet

Many aphid species feed exclusively on one type of plant. Some, such as green peach aphids, can feed on dozens of different plant species belonging to many families. Like the closely-related cicadas and scale insects, aphids feed passively on the sap of the plants' phloem vessels. The aphid punctures the phloem vessel, which releases the pressurized sap into the insect's food canal. Aphids simultaneously transmit viruses to the plant on which they are feeding, some of which can be lethal. Aphids usually eat citrus plants, potatoes, cereals, and sugarbeets, among other plants.

Aphids are required to extract an excess amount of sap in order to compensate for the low nutritional value of plants. In plants, the nitrogen compounds used by aphids to build proteins are low in density. After satisfying their nutritional requirements, aphids will expel the excess as “honeydew” from the recta. This has been known to occur on such a large scale that it resembles falling rain. Like the phloem of the plant, honeydew is generally very rich in carbohydrates. (Aphid)

The honeydew dropped by aphids can dot the finish or windows of cars underneath infested trees. When honeydew accumulates on branches and leaves, a fungus known as sooty mold grows and turns them black. Often the presence of sooty mold is the first visible sign of an aphid infestation. Other insects, in turn, will begin to feed on the deposits.

Organic insect sprays effectively eliminate aphids without harming your plants. They are made of all natural ingredients that are easily broken down by nature into elements the plants and the environment can use.

Aphid Control

Early detection is crucial to overcoming aphid infestations. Because some aphids may be airborne, checking plants weekly can help determine what's needed for controlling the infestation. Check the area around the bud and the undersides of leaves for colonies or clusters of young aphids. If the colonies are already appearing, this indicates that the insects have already established a presence on the plant and will begin to reproduce rapidly. If the number of separate colonies on plants is small, they can be removed by pruning or crushed by hand when found. This may be adequate in controlling the infestation.

For protecting ornamental plants and some kinds of trees, summer oils are effective against aphids. These oils suffocate the insects and disrupt their membranes. However, oils can sometimes injure foliage on some plants, so be sure to check to label when using on sensitive plants. The risk of foliage burn increases with high temperatures and other weather conditions. Oils should not be sprayed in the growing season. Additional applications are necessary as the oil is depleted.

Also effective against aphids are fatty acid salts and insecticidal soaps. These, like summer oils, disrupt the cell membranes of the insect. There is no residual effect, and insects must come in direct contact with them. (Townsend)

Fatty acid salts are effective because they incapacitate the aphids while not harming your plants. These acids attack the aphid’s central nervous system and weaken their outer shell. Insect sprays that use this as a primary ingredient are considered organic and are safe to use on vegetables and other garden plants.

Organic insect sprays only need to be applied once every seven to ten days while the aphids are present. This is an ideal method for organic gardeners who want to preserve the health of their soil and plants.

Predatory insects can also help control aphid infestations. Natural predators typically don't appear in large numbers until the aphid population has already increased, so this isn't usually the most effective method. Ladybugs, syrphid flies, and lacewings all prey on aphids. Especially in the backyard, naturally occurring predatory insects are best. Ladybugs can be purchased commercially and may temporarily control the aphid population, but they will usually only stay in your yard for a couple of days. (Flint)