Writer: Marlene Fritz (208/364-4010 in Boise)
Source: Ding Johnson (208/885-7543 in Moscow)

BOISE, Idaho--It doesn’t take an entomologist to identify your typical ladybug. The average four-year-old can finger the amiable red-orange beetle with its big black spots.

But it DOES take an entomologist to recognize that 40-50 different variations are all one and the same new Asian multicolored ladybug. Tan, yellow, orange, red or black--with no spots or up to 19--this voracious newcomer is now feasting on late-season aphids in ornamental and fruit trees from Weiser to Twin Falls.

Originally imported from the eastern Middle East a decade ago to control tree aphids in California and southeastern states, Harmonia axyridis has advanced inland to Midwestern and Intermountain states, arriving in Idaho by 1994.

"It has done some interesting things," says University of Idaho entomologist Ding Johnson, who is tracking its progress through the state. "It surprised everyone by being so exuberant in its ability to expand its range."

Indeed, entomologists at first feared that Harmonia axyridis would threaten Idaho’s native two-spotted ladybug, which similarly feeds on the aphids that leave ashes, lindens, maples and birches dripping with honeydew. But, instead, populations of the familiar "two-spots" appear to be holding steady.

According to Johnson, it looks like the Asian multicoloreds and the "two-spots" are peaceably job-sharing: the "two-spots" tend to do their good work in the spring and early summer, while the Asian multicoloreds come on late.

Consequently, while the Asian multicolored ladybug may wear scores of confusing uniforms, it could actually prove to be a heckuva team-player. "Instead of the problem I thought would develop, I really hope they will be a beneficial and tranquil addition to our state," Johnson says. "Their great potential is in giving us late-season biocontrol of tree-dwelling aphids. It’s quite possible that you wouldn’t have to spray."

So far in Idaho, no Asian multicolored ladybugs have been found north of Weiser or east of Twin Falls, where it may be too cold for them. Johnson says their pattern is consistent with tree-to-tree movement along river bottoms.

In Utah, however, some Harmonia axyridis have moved into the lower, or herbaceous layer, of plants–specifically alfalfa. "I think that’s likely to happen in areas where populations build up to huge numbers," he says. "We haven’t seen that yet in southern Idaho, but if it can happen in Utah, it’s not absolutely out of the question here."

Wherever they go in Idaho, Johnson is likely to be close behind. Every month during the past three growing seasons, he has teamed with Bill Clark, volunteer insect curator for Albertson College’s Orma J. Smith Museum of Natural History. Together, they sweep trees on the campus of Albertson College and Boise State University, then Johnson takes his net to the College of Southern Idaho campus in Twin Falls.

The last two springs, on oaks at Albertson College, they have found "thousands of ladybugs marching down the trees looking for food," Johnson says. The beetles–three native species and some Asian multicoloreds--were so thick that the "the trunks were covered, the ground was covered, we couldn’t help stepping on them."

This past July, four lindens at the Caldwell college were so buggy with Harmonia axyridis alone that the beetles were crawling out of Johnson’s and Clark’s nets before they could count them.

In the nation’s coastal regions, Asian multicolored ladybugs have "become unpopular" because of their tendencies to build up to huge numbers indoors as well as out, Johnson says. "They aggregate for the winter, sometimes in somebody’s house, and then you get a warm day in March and suddenly you have thousands of ladybugs running around your house. One USDA scientist actually developed an indoor light trap so people could collect them at night in their house and then throw them out the next morning."

Johnson suspects Idaho’s relatively cold winters are chilling out their potential for population flareups here. Not only are wintertime lows probably keeping them from becoming household pests, but they’re likely protecting the native "two-spot" from being eaten out of house and home by its imported competition.

That wasn’t the case for Idaho’s transverse and nine-spotted ladybugs, whose populations were severely curtailed by another introduced species, Coccinella septempunctata or seven-spotted ladybug. Released across the U.S. to feed on Russian wheat aphids, the seven-spotted ladybug wasted no time becoming a thug. It is now second in abundance only to the convergent lady beetle among Idaho’s roughly 80 lady beetle species.

Because even good bugs have the potential to go bad, scientists nationwide are currently reworking the criteria for releasing biocontrol agents in the U.S. Rules and regulations have long been in force, but entomologists say it’s clearly time to mend the holes in the nets.

In Idaho, while the populations of two-spotted ladybugs don’t appear to be in immediate danger, Johnson says our native tree-aphid-eater isn’t entirely out of the woods. "If my projection proves not to be right and if ultimately the Asian multicolored beetles get to be very abundant, we would lose or radically reduce our populations of two-spotted ladybugs," he says.