Are you seeing yellowing leaves, stunted growth, or an ugly black sticky substance on plants? This could mean you have aphids. As they move and feed, they secrete a substance called honeydew (not damaging) which quickly becomes infested with black scooty mold (damaging).
They often feed in dense groups on leaves or stems of plants as seen below. You may be wondering what kind of damage can they do and how to get rid of them...we'll share some tips.
What are aphids
Aphids are very small, and can be various colors - black, green, yellow, brown, red or pink. Some have a waxy or wooly appearance due to a secretion of a waxy or white substance. All aphids are pear-shaped with long legs and antennae. The distinguishing factor from other insects is a pair of tube-like structures called cornicles that project backward from the hind end of their bodies. Adult aphids are generally wingless, but some species have developed wings to be able to fly to other food sources.
Aphids have many reproductive cycles within a year. When the weather is warm, many species can develop from newborn to reproducing adult within 7-8 days. And because they can reproduce on their own, without a mate, an adult aphid can produce up to 80 offspring in a week. During colder weather, some species reproduce with a mate to produce a more hardy insect that will survive through the winter.
What kind of damage do aphids cause
In small populations, aphids are less of a threat. They are part of the eco-system that many other animals rely on. Ants love the honeydew that aphids produce, and predatory insects use them as a food source. When populations get out of control, the major damage occurs. If the honeydew is not consumed, it will grow black, sooty mold, which can harm the plant.
They can also transmit viruses into the plant causing yellowing, stunted growth, and curling leaves. A few aphid species live in the soil and can even attack roots. Although aphids rarely kill a mature plant, the unsightly presence of them and the black mold is reason enough to want to control them.
How to treat your plants and trees if you have aphids
Many aphids prefer the underside of leaves, so be sure to check there when monitoring plants and trees. It's best to catch infestations early so you can use a hose to spray them off or prune them out. There is more than one way to control aphids, biological and chemical.
Natural enemies can do a great job controlling aphids. Lady beetles, lacewings or parasitic wasps will feed on aphids. You can also bring in plants like nasturtium, mum, aster, hollyhock, or larkspur that attract aphids to lure the insects away from the plants and trees you want to protect. Controlling ants can be helpful as well. Since ants feed on the honeydew, they tend to protect aphids. If you see large amounts of ants going up an aphid-infested tree trunk or stem, place a band of sticky material like Tanglefoot around the trunk to stop the ants. If the tree is young, do not apply directly on the tree, use fabric tree wrap or duct tape underneath.
Remember that small populations can be tolerated by most plants. If insecticides are needed, try an insecticidal soap or oil, such as neem or canola oil. These products will kill aphids by smothering them, so be thorough when applying. The mixture should only be 1-2% oil solution in water. Applications may need to be repeated as the solutions only kill the aphids present the day of treatment. There are stronger products available but they are not as safe and will also kill large amounts of the aphid's natural enemies.
Have questions about aphids and your level of infestation? Call Pure Green. Our experts can evaluate your lawn and help you determine a course of action.