Natural enemy attractant
An extract of catnip attracts lacewing adults.
Chemist Kamal Chauhan observes lacewings in a trap containing the pheromone he identified as iridodial.
A natural attractant that can lure lacewings into farms and orchards is being commercialized.
Dr. Kamal Chauhan at the U.S. Department of Agriculture's Chemicals Affecting Insect Behavior Laboratory in Beltsville, Maryland, believes the attractant could enhance biological control of aphids and other small pests.
He and ARS entomologist Dr. Jeffrey Aldrich, found that a catnip extract called Z,E-nepetalactone, which is a component of the sex pheromone for many aphids, attracts both lacewings and aphids. But, a relatively minor impurity from the extract, called iridodial, attracts only lacewings.
A male lacewing has 10,000 glands on its abdomen, which release a pheromone. The researchers tested the contents of the abdomen of a male Chrysopa oculata lacewing and found that the chemical structure of the pheromone matched that of iridodial. Though the pheromone is produced only by males, it appears to be an aggregation pheromone that attracts both males and females. For example, a male lacewing might go off in search of food and use the pheromone to call other males and females to a food source.
Chauhan said there are perhaps 1,000 species of lacewings, that fall into two genuses: Chrysopa and Chrysoperla. His research shows that iridodial attracts many Chrysopa species, including Chrysopa nigricornis, which is found in Pacific Northwest orchards, but not Chrysoperla.
Chauhan envisions that orchardists would place lures containing iridodial in or near the orchard to establish local populations of lacewings that would control aphids and other pests. Lacewings need moisture and some shade, and so might thrive better on vegetation outside the orchard. The attractant will only be effective if there are already natural lacewing populations in the vicinity that will be drawn to it. The product has been tested in peach orchards in Georgia.
Currently, growers who release lacewings in their orchards buy them as larvae or eggs. Chauhan said if the larvae don't find a good source, they might not survive.
The attractant has the advantage of drawing in adults to establish and build natural populations. Lacewing larvae have a voracious appetite for aphids, while lacewing adults feed primarily on aphid honeydew, pollen and nectar. However, Chrysopa adults will also eat insects, Chauhan said.
Iridodial is not a new product. It can be extracted from various species of ants and is sold on the Internet as an expensive health supplement for treating cancer. It was not previously known to be a pheromone.
Chauhan said his method for extracting iridodial from catnip oil is a complex but economical way to make relatively large amounts for commercial agriculture. Iridodial is potent. Just 25 milligrams (one ten-thousandth of an ounce) are sufficient to treat an acre of land. The method is being patented, and the attractant is being commercialized by Sterling International, Inc., of Spokane, Washington, for both domestic and international markets. Chauhan expects it to progress rapidly through the U.S. Environmental Protection Agency's registration process, since it's a natural product that's been used as a pharmaceutical ingredient, and believes it could be registered by next year.