Gardeners: Don’t Worry About Aphids
By Susan Jongeneel, University of Illinois
URBANA -- Aphid lion larvae are out and eating approximately 400 aphids a week. They are competing with lady bugs, parasitic wasps, minute pirate bugs, hover fly larvae, predator stink bugs, praying mantises, assassin bugs, and damsel bugs. With this plethora of beneficial insects on the job, University of Illinois horticulture educator Kelly Allsup urged gardeners not to use chemical sprays to get rid of aphids.
Aphids are phloem feeders, or plant-sap suckers. They congregate on the growing tips of garden plants or on the underside of the leaves. They are small and round and produce a frass (excrement) called honeydew that collects on the plant leaves, making them sticky.
A garden’s aphid population builds at a very high rate due to asexual reproduction by the females giving birth to already pregnant clones. A female aphid can produce 5 to 12 offspring in one day.
Green lacewing (Chrysoperla or Chrysopa spp.) are one-half to three-fourths of an inch long. They have green bodies, golden eyes, and intricate lace wings that they hold upright over their bodies.
The green lacewing adult will fly from flower to flower eating nectar, pollen, honeydew, and small insects. When an adult female comes across a patch of honeydew and aphids, she will lay her white, oval eggs, which remain connected to the plant by a thin filament.
The green lacewing larvae, or aphid lions, have hooked jaws protruding from their heads, making them look more like miniature alligators than lions. As soon they hatch, they begin eating, injecting enzymes into their prey that digest the internal organs. They then suck out the liquidated body fluids. The larvae will eat spider mites, small caterpillars, thrips, mealy bugs, whitefly, and other soft-bodied invertebrates.
Aphid lions will eat for 1 to 2 weeks before pupating in white, round, silken cocoons on concealed parts of the plant. Adult green lacewings emerge and live for 2 to 3 months. Depending on the genus, the insects overwinter in bark crevices or protected locations either as adults or in the pre-pupae stage. They emerge next spring when flowers appear. Depending on temperature and weather, there can be one to four generations per year.
“An infestation of aphids could be just what your garden needs to increase diversity,” said Allsup. “The aphid population will attract beneficial insects and pollinators as well as the birds, bats, and larger insects looking to dine on them.”
Many chemicals labeled for garden use can harm beneficial insects and prevent their return. “Treat only if you see severe plant decline or suspect aphids or phloem feeders are transmitting disease,” Allsup said.
As a first step, use water sprays or biopesticides such as soap or neem oil. An alternative to chemical sprays is to release beneficial insects bought online.
“Above all, inspect your garden plants and look for signs of garden pests and the beneficial insects that prey on them,” Allsup advised.