Look for Lacewings - May 21, 2008
Jeff Schalau, Associate Agent, Agriculture & Natural Resources, Arizona Cooperative Extension, Yavapai County
Most insects in your landscape, orchard, or vegetable garden do not feed on or harm plants. Insects need to be somewhere, and sometimes they are just passing through or resting as they go about their business. Yes, there are plant feeders of which most gardeners are ultra-aware and call “pests.” However, other insects are looking for a meal and eat the “pest” insects. These beneficial insects are either predators that kill and feed on pests or parasitoids which have larvae that parasitize and may kill the host but live freely as adults. In many cases, the activities of these beneficial insect species can completely prevent or greatly limit pest problems.
Learning to recognize these beneficial insects is an important skill gardeners should learn so they can weigh their options before applying pesticides or other actions. Most gardeners are aware of the predatory habits of lady beetles (ladybugs) and can identify the adults, but they may not be familiar with the egg masses and larvae which are often described as resembling a small Gila monster. Similarly, lacewing adults are often recognized when they fly to porch lights, but the eggs and larvae are less conspicuous. Yet lacewings are also beneficial predators of pest insects.
Green lacewings (Chrysoperla spp.) are common in Arizona gardens and landscapes where pesticides are not regularly applied. Adult green lacewings are delicate, pale green insects from 1/2 to 3/4 inch long. Their four wings have many veins, which gives them the net-like or "lace" appearance. They are attracted to lights at night and may be mistaken for moths except they have a characteristic fluttering flight when disturbed. Green lacewings also have an objectionable odor when handled. Brown lacewings (Hemerobius spp.) are also found in Arizona but are not as common and are roughly half the size of green lacewings.
Green lacewings lay their pale green eggs on the tips of threadlike stalks on the underside of leaves. Brown lacewing eggs are not on stalks. Both green and brown lacewing larvae hatch within a few days. They are about 1/4 inch long, alligator-shaped, and light brown or grayish in color. They have six legs, with large sickle-shaped mandibles and are voracious feeders consuming large numbers of aphids (they are also called aphid lions). Green and brown lacewing larvae also feed on other insects, including moth eggs, mealybugs, small scales, mites, whiteflies, lace bugs, other small insects, and when nothing else is available, each other.
Larvae of both species feed for two to three weeks before pupation. When the larvae mature they form a small silken cocoon on an inconspicuous plant part in which to pupate. Adults emerge in about five days, but some species may overwinter in the cocoon. Green lacewing adults are active at night and feed on pollen, nectar and honeydew (the exudate of aphids and other sucking insects). Brown lacewings continue to feed on small insects as adults.
As a skilled gardener, it is your mission to inspect your garden and landscape plants for signs of beneficial insects. Look for lacewing eggs on leaf surfaces. When you see aphids, look for lacewing larvae (and other beneficial insects as you learn to recognize them). If you are very observant, you may find a lacewing cocoon. The presence of adult ladybeetles is always a good sign. Evidence of other beneficial insect activity is empty skins of aphids and other insects. These empty aphids are called mummies and it is likely the pests were parasitized by Trichogramma wasps or another other small predator.
When you see beneficial insects or their signs, you should give serious consideration before using insecticides. Beneficial insects are slower to recolonize after insecticide applications and using them may give a competitive advantage to the pest species. To help you recognize lacewings at each life stage, I have provided links to information and photos below.
The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at email@example.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/.
Green and Brown Lacewing Information and Photos from University of Kentucky Cooperative Extension Service
Brown Lacewing Information and Photos from the University of California IPM On-Line
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Last Updated: May 15, 2008
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