Not your sweet ladybug any more
As with most actions that result in a cascade of unintended consequences, the USDA’s deliberate introduction of Harmonia axyridis, theMulticolored Asian Lady Beetle (or MALB) into the U.S. some thirty years ago, seemed like a good idea at the time. An aggressive and voracious predator of aphids, scale, mealybugs, and other insect pests in its native Japan, the MALB was released mainly in the southern states as a beneficial biological control in pecan and fruit orchards, ornamentals, wetlands and pine forests, and in agricultural crops such as soybeans and alfalfa. The MALB thrived and quickly spread throughout North America. On one hand it has indeed proven beneficial (especially against pests of trees and shrubs), but it has also created some not inconsiderable (and, one might think by now, not altogether unpredictable) ecological and economic havoc in its predatory wake.
Often mistaken for its well-known, less aggressive native cousin, MALBs come in many color forms, from dark red to bright orange or yellow (thus it is sometimes called the Halloween lady beetle), with as many as nineteen or more black spots –or no spots at all. Spots may be a MALB sex-linked trait; the more spots, the more likely the beetle is female. Color variations are a key to what the MALB has been eating, and what the ambient temperature was during life cycle development. Bright red equals lots of aphids; yellow equals fewer aphids but more pollen consumed.
Mated females lay their eggs in spring on the underside of leaves near aphid colonies. One female can lay as many as 3,000 or more eggs per generation, and the development of egg through larval and pupal stage to adult takes about one month. This allows for five or six generations a year, and adults can live up to three years. In other words, a mushrooming MALB population, helped along by the USDA’s initial successive releases, climate-change support of food source insects, and the possibility that garden supply houses may have shipped large quantities of MALBs to customers over the years as “ladybug” biological pest controls.
And this beneficial aspect cannot be dismissed; MALBs will prey on the eggs of moths, beetles, mites, thrips, and many other soft-bodied insect pests, thus obviating at least some of the need for chemical sprays. Unfortunately, MALB larvae (which look a lot like miniature alligators) also prey on monarch butterfly caterpillars, as they are one of the few predators that can tolerate the monarch’s powerful defensive toxins. The indigenous nine-spotted lady bug, a beneficial predator of aphids and other plant pests in its own right (and the official New York State insect), may have already been out-competed by the MALB. Entomologists at Cornell University claim the ladybug of song and poem has not been seen in the eastern United States since 1984.
Moreover, MALBs have become a serious pest of some fruit, most notably grapes, which they will feed upon in a plague-like mass. Worse than the feeding damage itself, if crushed up with grapes in the wine-making process, MALBs impart a revolting flavor to wines and juices. In 2001, vinters in Ontario, Canada, were forced to dump nearly a million liters of wine tainted by the alkaloids of MALB bodies. As a result, vineyardists in Canada and the U.S. have been advised to apply yet another chemical — a specific “pesticide of choice for MALBs” — to their grape crops just before harvesting.For most people, the main (and increasing) problem with the MALB is its habit of entering homes in large numbers with the onset of cool weather. While they don’t harm structures or chew wood, on warm winter days the MALBs become active and swarm on windows and light bulbs, furniture, kitchen surfaces, and on food, which they will infest and spoil. If disturbed or crushed, MALBs will secrete a noxious orange fluid that stains fabric and wallpaper (and even skin). The off-putting smell of this fluid can contaminate closed spaces such as closets, cupboards, and vacuum cleaners (the advice on this last is, literally, put a sock in it –that is, insert a knee-high stocking in the hose to catch the vacced-up MALBs and dispose of them, in the tied-off stocking, outside).
This is the same alkaloid fluid that ruins wine. It is the MALB defense against its own predators, and it is so effective that ants and spiders will not go near sugar baits that have been treated with MALB secretions. This fluid, as well as MALB fecal matter, may account for the reports of human MALB-allergic reactions, which include cough, runny nose, conjunctivitis, and asthma-like symptoms similar to cockroach sensitivity. Moreover, MALBs bite! Which takes many homeowner by surprise, to say the least. And if that isn’t enough, an article on the Ohio State University Pest Management web site cautions, somewhat unnecessarily, that “if these beetles break the skin and are allowed to continue, they will feed on the wound for as long as thirty minutes.”
Most assuredly not your sweet outdoors leaf-litter overwintering ladybird –“Little Cows of the Virgin” in France and used, mashed up, as late as the 1800s, to treat measles and toothache– any more.
Eventually, natural controls will catch up with the MALB –in fact there is a type of parasitic wasp that already seems to be targeting its numbers. Meanwhile, a flightless MALB strain has been developed in European labs; whether releases of this variety will help slow the MALB’s spread has yet to be seen. Home-made traps and deterrents such as black light attractants and house-siding applications of diatomaceous earth seem helpful to some extent; one website suggests spraying closets with menthol since MALBs can’t stand the odor (as who can?) Preventing their entry into the home is probably the first and only real line of defense: Before cool autumn weather sets in, seal cracks and openings around windows, doors, siding, and utility pipes with a quality silicone caulk; repair window screens and screen vent openings; remove dead MALBS as soon as they appear, since their presence may be themselves an attractant to other MALBs.
And don’t mailorder “ladybugs” or other insects to release in your garden. They that have wings shall find it on their own, soon enough.
(Add other pest management remarks, etc.)
Fact Sheet: The Multicolored Asian Last Beetle, The United States Department of Agriculture, www.ars.usda.gov/is/be/beetle
“Multicolored Asian Lady Beetle” by R.L. Koch and W.D. Hutchinson, Department of Entomology, University of Minnesota www.vegedge.umn.edu/VEGPEST/Harmonia/Harmonia
“Multicoloured Asian Lady Beetle (MALB)” by Kevin W. Ker, M.Sc.P.Ag and Neil Carter, M.Sc., 2004, 2004
“What’s Happening?”The University of Tennessee/Agricultural Extension Service, Entomology & Plant Pathology EPP#60.
Biological Control: A Guide to Natural Enemies in North America, by Catherine R. Wreeden, Anthony M. Shelton, and Michael P. Hoffmann, www.nysaes.cornell.edu/ent/biocontrol/predators/harmonia
“The Lady Beetle News,” Ohio State University Integrated Pest Management (IPM) Program, Sept. 2003 www.ipm.osu.edu/lady/Sept03.pdf
“The Unlucky Lady Bug” by Jane Firstenfeld, Wines&Vines, www.winesandvines.com
Blog: Maine Farmhouse Journal, www.crabcoll.com/whatsnew
“Ladybug, Ladybug, Fly Away Home (cue the ominous music)” April 10, 2006; from the Blog “Walking the Berkshires/ Invasive Species” http://greensleeves.typepad.com/berkshires/invasive_species
Secret Weapons: Defenses of Insects, Spiders, Scorpions, and Other Many-Legged Creatures by Thomas Eisner, Maria Eisner, Melody Siegler, 2005 Belknap Press of Harvard University, Cambridge.
Peterson First Guides: Insects, the concise field guide to 200 common insects of North America, Christopher Leahy, 1987, Houghton Mifflin Co., New York.