Know Your Friends

Green Lacewings

Green lacewings are predators found in most environments. Several species of Chrysoperla and Chrysopa are important predators. The common green lacewing occurs throughout North America, while other species are more restricted in distribution. The light green adult has long, slender antennae, golden eyes, and large, veined, gauze-like wings that are 1/2 - 1/3 inch long. It is a slow-flying, nocturnal insect that feeds on nectar and pollen, and it emits a foul-smelling fluid from special glands if captured. The female lacewing lays eggs usually in groups on leaves, each egg held away from the leaf surface on the end of a slender stalk. A female lays up to 300 eggs over a period of 3-4 weeks, but often it does not survive that long in the field.

The larva, commonly called an aphidlion, resembles a green-gray alligator with mouthparts like ice tongs. An aphidlion seizes and punctures its prey with long, sickle-shaped jaws, injects a paralyzing venom, and sucks out the body fluids. After feeding and growing to 1/2 inch in length during a 2-3 week period, the larva spins a spherical, white silken cocoon in which it pupates. The adult emerges in about 5 days through a round hole that it cuts in the top of the cocoon. It overwinters as a pupa within its cocoon or as an adult, depending on the species.

An aphidlion is a voracious feeder and can consume up to 200 aphids or other prey per week. In addition to aphids, it will eat mites and a wide variety of soft-bodied insects, including insect eggs, thrips, mealybugs, immature whiteflies, and small caterpillars. Aphidlions will also consume each other if no other prey are available.

Green lacewings are available from many commercial suppliers, generally offered as eggs. The released aphidlions move around a lot and will travel 80-100 feet in search of prey. Once their food source is exhausted they will leave the area. The predatory larvae feed for 2-3 weeks before they become adults. The adults must have a source of nectar, pollen, or honeydew to feed on in the general vicinity of the pest area to stimulate egg laying, or they will leave. Providing an adequate food supply and suitable adult habitat can contribute to lacewings remaining and reproducing in the crop. Additional releases can provide a continuous supply of larvae if adults do not stay and reproduce.

The number of lacewings needed for effective control depends on the pest population and climatic conditions. For control of moderate aphid infestations in home gardens, 5-10 lacewing eggs per plant or 1,000 eggs per 200 square feet are recommended. General release recommendations for most crop situations start at 5,000 per acre for each application, but much higher rates may be necessary. Two or three successive releases made at two week intervals are better than a single release. Suppliers usually make recommendations based on specific situations. These insects are extremely effective under certain conditions, especially in protected or enclosed areas such as a greenhouse, but they may fail to survive and provide control when conditions are not favorable.

- Susan Mahr, University of Wisconsin - Madison

Drawing by Michele Schwengel. Photo by Susan Mahr.
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