Aphids are also known as “plant lice”. If that’s not enough to make you want to keep them out of your garden, consider that there are about 4,400 species, 250 of which are serious problems for farmers and foresters and people like us. They are, in fact, one of the most destructive pests of cultivated plants.
Aphids are tiny little sucking insects, 1/8 inch or smaller. They suck the juice out of plants, much like chinch bugs suck the juice out of grass. As if that isn’t bad enough, they can also transmit plant virus diseases.
A female aphid can produce 50-100 little aphids in her lifetime, and those can begin reproducing in 6-8 days. Most aphids are female and reproduce live young without mating. Most aphids are wingless, too, but when colonies of aphids get too crowded, or they’re tired of the host plant they’re on, they produce winged aphids that fly off and start a new colony.
Aphids can destroy your flowers, shrubs, even trees. They procreate so quickly that you can have a big problem before you know it.
Inspect your plants. Early detection is everything! Yellowing of leaves and deformed new growth are symptoms. Look on stems and on the undersides of leaves. Aphids can be white, green, yellow, red, even black, depending on the species. Green or white aphids are the most common in our service areas. They’re so little, that one is hard to see, but by the time you would notice them, there are usually hundreds of them. Most of the time, they look white or pale green.
If you notice aphids, have them treated or treat them yourself quickly. In the meantime, you can snip off leaves or branches that are yellowed and infested to slow the destruction. Or, spray the plants off with a water hose – this won’t get rid of the problem, but it will dislodge the insects and interrupt their feeding, and those sprayed off probably won’t get back on the plants.
Our tree and shrub program includes spring and fall fertilizations to help your plants stay healthy and be more resistant to infestations, but we also spray your trees and shrubs at intervals throughout the spring and summer to keep insects at a controllable level. If you’re doing your own spraying, bear in mind that different insects come out at different times. There are many generations of the same insect throughout the summer, so multiple sprayings will be necessary.
If you prefer to treat the aphids yourself, read on:
If you have aphids on vegetable plants or fruit-bearing trees, use a product containing permethrin, a derivative of marigolds. This isn’t long-lasting and is safe for vegetables or fruit. (Always read the label to be sure it’s labeled to control aphids and that it’s safe to spray on food.)
Note: here's a great article from Oklahoma State University on Home Vegetable Garden Insect Pest Control.
For other plants, buy a product that contains bifenthrin or cyfluthrin. These are longer-lasting and will do a good job.
Be sure to spray on the undersides of leaves.
Applying dormant oil (horticultural oil) in cold temperatures before spring leaf-out will sometimes head off and prevent aphid infestations.
Ladybugs are natural predators of aphids, and you can buy these to release in your garden. Lacewings will also eat aphids and can be attracted by planting dill, coreopsis, sunflowers, cosmos and (don’t laugh) dandelions!
Science note: Aphids are remarkable in that they are the only known member of the animal kingdom that can synthesize carotenoids (pigments from plants, algae, fungi & bacteria) by horizontal gene transfer. Horizontal gene transfer is the process of incorporating genetic material from another living organism without being that organism’s offspring. Aphids demonstrate this by picking up red pigment from fungi, turning themselves red instead of their normal green. Amazing that something referred to as “plant lice” is the only living creature with this capability!