By Karen Miller, Master Gardener, Entomology Specialist
Aphids, aphids, and more aphids! What are aphids and where do they come from? In the order Homopterous and the Aphididae family, aphids are small soft-bodied insects with long slender mouthparts used for piercing and sucking. These mouthparts are used to draw sap from the plant tissues.
Aphids are found worldwide, but are most commonly found in regions with relatively moderate temperatures. Almost every plant has one or more aphid species that occasionally feed on it. Aphids are pear-shaped, with long legs and antennae, and come in many colors. The color of the aphid depends on the species and the plant it feeds on. Adults can be winged or wingless and usually have a pair of tubes called cornicles protruding out of the upper end of the abdomen. These cornicles are used to spray an oil or waxy fluid on enemies.
Aphids are one of the most prolific insects and considered one of our biggest pests. It is believed that over 200 species exist and may produce over fifty generations in one year. Some species produce several generations without mating. The females can lay eggs or give live birth, and those already have within them developing embryos for the next generation. If the host plant becomes overcrowded, some aphid species will produce winged offspring that will move on to other food sources.
Although aphids seldom kill a plant, their damage and unsightly honeydew sometimes warrant controlling this pest. Always consider nonchemical controls first. Natural enemies can be very effective in controlling aphids. Various species of parasitic wasps will lay their eggs inside the aphid, using it as food for the larvae, lady beetles, adult and larvae, lacewing larvae and the larvae of the syrphid fly are predators that feed on aphids. Cultural control would be another nonchemical method of controlling the aphid. Aphids often build up on weeds like sow thistle and mustards and will move onto your crop seedlings after they are planted in the garden. It is good to check out the surrounding areas for sources of aphids and remove them before planting your veggies. Also, check for aphid infestation on plants before you buy them. Nonchemical control can be as simple as a strong spray of water to knock the insect to the ground.
Most dislodged aphids will not be able to return to the plant. They will either die from the impact to the ground or by starvation. By using this method early in the day, the plants will have the chance to dry off and be less susceptible to fungal diseases. If you are one of those impatient gardeners, there are selective insecticides, such as oils and soaps that are available and safe to use. These can provide effective long term control because they do not harm the natural enemies of the aphids.
Bottom line: While researching the aphid, I came across an interesting tidbit. Ants and aphids are friends! The ant feeds on the honeydew the aphid excretes, and in return, the ant protects the aphids from their natural enemies. Some ant species actually gather and store the aphid eggs in their nest over the winter. In the spring, the ants carry the newly hatched aphids back to the host plant. Go figure!?!