How to Identify and Manage Aphids

Aphids are not often a common problem in the interior landscape, but occasionally they can show up. These tiny insects, also known as plant lice, may cause the leaves of plants to become deformed and sticky. If they are in high enough numbers, aphids will stunt a plant’s growth.

Why Are Aphids So Destructive?

Both immature and adult aphids feed on plants by sucking plant juices, which distorts the plant’s leaves. A quick-growing infestation can drain the sap from a plant until it’s stunted or dying. Like other insects that share the same feeding method—piercing and sucking mouthparts (like a straw)—aphids secrete a sticky fluid called honeydew. Honeydew can attract other insects such as ants, which like to feed on the sweet material. Because it builds up quickly due to aphids’ very fast reproduction rate, honeydew can become a problem in the interiorscape, sticking to windows, planters, and other surfaces. Over time, the buildup of honeydew allows for a black mold (sooty mold) to grow on the sticky surface. This soot becomes unsightly over time.

How to Identify This Pest

Aphids are tiny but easy to identify. They can vary a little in size, but aphids are generally pear-shaped and have two tubes at the tip of their abdomens extending backward. Colors vary depending on the species and host plant. Most aphids are wingless, but once a plant’s sap has been nearly depleted or the aphid population on a plant is very high, some species will develop wings and search for new plants to infest. When looking for aphids, you will often find them on new growth. Also, there are some species that live and feed on the roots of plants.

The Life Cycle of an Aphid

Aphids can be a problem for indoor plants because of their sheer numbers. Female aphids can reproduce without mating; giving birth to live immature aphids and skipping the egg-laying stage. In an outdoor setting, when temperatures drop in the fall, aphids will lay eggs, but because of the warmer interiorscape environment, there is no need to overwinter as an egg. Immature aphids, which look like smaller versions of adults, begin to feed immediately, stressing the plants even more. Young aphids molt (shed their skins) 4 times before becoming an adult. The common green peach aphid, Myzus persicae, under optimal conditions, can complete its life cycle in 10-12 days.

Do You Have an Aphid Infestation?

Clear indicators:

• Sticky honeydew
• White skin flakes (as aphids molt, they leave behind white skin flakes, which are sometimes confused with whiteflies)
• Ants

A plant struggling with an aphid infestation may have curled, yellowed or mottled leaves, stunted growth of buds and branches, deformed buds, or even plant death. Watch for ants. If you see ants running up and down a plant, that is often a good indicator that there is some kind of honeydew-producing insect present.

It’s Time to Take Back Control

Aphids might have strength in numbers, but it’s possible to mitigate the damage they cause and help prevent future infestations. Start by washing the plant, which can easily knock off aphids. If necessary, prune the heavily infested parts of the plant. If washing and pruning are not an option, there is biological control. Beneficial insects, like lacewing larvae, provide excellent control in the interior landscape. Not only do they feed on aphids, but they also feed on other soft-bodied insects.

Spray options, such as insecticidal soaps or horticultural oils, are also available. Be careful not to overspray because these compounds could make floors slippery or damage surfaces. Chemical insecticides like Safari (dinotefuran) and Flagship (thiamethoxam) can be used as a very effective drench. With drenching, you do not have to worry about overspray. Another spray option is Endeavor (pymetrozine). This is a foliar-applied insecticide that paralyzes the mouthparts of aphids, preventing them from feeding. It is compatible with many biological control agents.

Pest control labels vary between states, and the pesticide user bears the responsibility of consulting the pesticide label and adhering to the law. Always read the label before applying a pesticide to make sure it is legal to apply on your site, in your state, and to the plant material.

Preventing Aphid Infestations

To prevent aphids, keep an eye on your plants and be sure not to over-water or over-fertilize them. Aphids thrive in environments with high nitrogen. Also, inspect all new incoming plants. Aphids are a tough pest to control, but staying vigilant and using safe insecticides can help you beat the tiny bugs before they take over your landscaping.

Battling other common indoor plant pests? Check out my Professional’s Field Guide to Plant Pest Control for information on spider mites, whiteflies, thrips, fungus gnats, mealybugs, and scale insects.

“Ants and aphids on snakeroot” photo by Dendroica cerulea via https://www.flickr.com/photos/dendroica/6170146527/