Aphids

Aphids are everywhere. If you grow perennials outdoors they are everywhere in the environment. If you grow indoors, there are probably a few lurking around most of the time.

Aphid populations can quickly get out of hand, but luckily they can be easier than other pests to kill. Since they are soft-bodied and slow-moving, they are very susceptible to insecticidal soaps and oils. This can often be your first line of attack to reduce aphids and protect beneficial organisms and workers.

Aphids are also heavily attacked by many biological control organisms that can be released into your greenhouse or that find them naturally in outdoor crops. These include predators like lady beetles, green lacewings, hoverfly larvae but especially parasitoid wasps that lay eggs inside of the aphids.

Facts about Aphids

whitney cranshaw CSU, University of Georgia, Bugwood.org

Identification: Aphids are small (1-10 mm) and pear shaped. Colors vary by species, but the more common colors are green, red, yellow or black. They can be smooth or some of the more ornate, “woolly” aphids may have white fluff similar to mealybugs. To distinguish the aphid from another pest like a scale, look for cornicles—two “tail pipes” that extend from the end of its body.

Sometimes aphids have wings, which can throw off a positive identification. To alleviate colony overcrowding, some aphids will develop wings, helping them to fly to new food sources and unfortunately, also potentially develop new colonies.

Detection: Look for shiny patches of honeydew on leaves then inspect the leaves above for aphids. Monitor plants in spring and early summer to determine if intervention is needed.

When scouting, look closely to make sure that what you are looking at are live aphids. Newly born aphids will feed and molt four times before becoming an adult. When they molt, they leave behind their old skins on the surface of the plant, which look like white flakes. This can easily be mistaken for whiteflies or other pests, so use a 10x hand lens to confirm identification.

Cultural control: Aphids and many other pests thrive on plants that are under stress or that have received nitrogen fertilizer. Both of these factors can reduce plant defenses and make them more nutritious for pests.

Mechanical control: Aphids typically occur in groups that can be pruned from a plant. A single rose stem may have a dense colony of aphids whereas the rest of the plant may be clean. Removing the infested stem could fix the problem and negate the need for insecticides. Aphids and aphid colonies can also be dislodged with a stream of water.

Biological control: Aphids have a lot of natural enemies, like ladybird beetles and their larvae, green lacewings and their larvae which sometimes disguise themselves with debris, hover fly maggots, parasitic wasps and entomophagous fungi. Often, as aphid populations grow, natural enemies colonize in sufficient abundance to reduce the population.

Chemical control: Natural enemies are not always able to keep aphids under control, so chemical control is needed. Aphids are soft-bodied and can usually be killed with insecticidal soap or horticultural oil instead of more toxic products.