As soon as your favorite flowers or vegetable plants pop up, aphids are ready to pounce. They'll stay on the stems and underside of leaves until fall, sucking up the sap until your plants wither and die. They secrete a gooey called honeydew which ants love to eat, and honeydew left on the plants often turns black with sooty mold fungus. Aphids can act as conduits for viruses which they spread from plant to plant. Fortunately, there are several options to prevent and control aphids.
What Are Aphids?
Aphids, also called plant lice, are small (up to ¼ inch) soft-bodied insects that can infest most garden plants. Some aphids spend their entire lives on one type of plant; others infest different varieties and move from plant to plant throughout the season. Most gardeners can readily identify green aphids, but black, brown, yellow and gray aphids are also common.
How to Prevent Aphid Infestations
- Monitor your plants. Beginning early in the season, check your plants frequently for the presence of aphids, paying close attention to plants you've found aphids on before. Aphids are most active when temperatures are warm or hot and often cause the most damage to plants in late spring. Their favorite plants to infest are non-woody, blooming plants like zinnias, dahlias, cosmos, and asters.
- Check for ants. Ants like to “farm” aphids to collect the honeydew they produce. If you see a lot of ants hanging around your plants, it could be a sign that aphids are present
- Plant onions. Aphids dislike the smell produced by members of the onion family. Planting flowering onions, garlic, and chives throughout your garden can help discourage aphids.
- Don’t over fertilize your plants. Aphids love to feed on plants with high nitrogen levels and soft, lush growth. Whenever possible, fertilize your plants with a slow-release fertilizer that releases nutrients gradually over time.
- Catch the problem early. If you catch an aphid problem early, you can remove any infested branches or hose them off with cold water.
Natural predators are another way to keep aphid, and other insect pest, populations in check and reduce the need for chemical controls. Several predatory and parasitoid insects as well as spiders feed on aphids. Ladybugs, ladybug larvae, soldier beetles, hover flies, predaceous midges, big-eyed bugs, lacewings, parasitic wasps, hornets, yellow jackets, spiders, and assassin bugs all feed on aphids. Predators do not show up in the garden until there is a food source present, so there will be a gap between the appearance of aphids and the appearance of predators.
If spraying your plants with water isn't working or your aphid problem exploded faster than your predator population could handle, there are many different chemical control options for every areas of your yard. On your roses and ornamentals, use Ortho® Insect Killer Rose & Flower Ready-To-Use. For aphids in multiple areas of your garden and landscapes, use Ortho® Insect, Mite & Disease 3-in-1 Ready-To-Use for small jobs and Ortho® Tree & Shrub Fruit Tree Spray for large jobs. Always check the label to make sure your plant is listed before applying, and always follow the directions for use.