When is it too much of a good thing?

For many homeowners in Western North Carolina, the answer is now. From now through mid-November many will be invaded by Asian hordes.

The Asian lady beetle, Harmonia axyridis, has a penchant for swarming homes and other structures in the fall, looking for good overwintering sites. In its native homeland — from southern Siberia through China to Korea and Japan — the Asian lady beetle swarms cliffs, mountainsides and rock outcroppings, seeking crevices in which to spend the winter. Here, structures appear to offer an acceptable alternative.

Illumination and brightness appear to be strong attractants. Light-colored homes and buildings with south and southwestern exposure are virtual ladybug beacons. Because H. axyridis forages in trees and often flies well above tree top level, ridge top and mountain top homes are particularly susceptible.

While ladybugs in the wild are beneficial, feeding primarily on different species of aphids, thousands swarming around one’s home, often finding their way inside, can create a nuisance. It’s kind of like your extended family coming for the holidays. You’re glad they’re there, you just wish they would stay at someone else’s house.

According to Jim Costa, entomologist at Western Carolina University, lady beetles emit an aggregating pheromone in the fall. While this pheromone is not as intense as breeding pheromones, its effectiveness is multiplied by numbers. As more lady beetles congregate, the stronger the pheromone becomes, creating swarms of insects.

Prevention is the best way to protect your home from these swarms. Caulk or seal crevices and openings around windows, doors, facia boards, soffits, utility openings, dryer vents, etc. Be sure window screens and screening around attic vents are in good repair.

For older homes and/or large multi-story structures, this can be quite a chore. One may have to decide what his/her ladybug tolerance is and work from there.

Exterior application of pesticide by a professional pest control company may offer some relief, but timing is the key. If you spray too early, the insecticide is not effective when the beetles arrive. If you wait until they arrive, many will make it into interior spaces and the spray will be ineffective. And, of course, you are increasing the toxin level around your home.

Spraying inside is even a stickier proposition. The hardy little beetle must be sprayed directly or crawl across treated surfaces for the insecticide to be successful. Once again, this increases toxin levels, and now, it’s inside your home.

One way to deal with ladybugs inside your home is to vacuum them. If you mash or swat them they generally emit an orange colored fluid which can stain. For those with a soft spot for these cute beneficial creatures, a handkerchief can be placed between the vacuum hose and the dust collection bag or area and the ladybugs can be trapped and relocated.

These quarter-inch long, yellow to orange bugs with black spots are harmless to humans. In the spring they will leave your home and once again begin their summer time life cycle. First they will find food, then the females will lay her eggs.

Each adult female may lay up to 300 or more eggs in a lifetime. Eggs are generally laid in clusters of 10 to 50 on the underside of leaves, in aphid colonies. The eggs hatch in three to five days and immediately begin to gorge themselves on the aphids. After two to three weeks the larvae pupate. In seven to 10 days the adult emerges.

Both the larvae and adult feed on aphids. A larvae will eat as many as 400 aphids before it pupates. An adult ladybug may eat as many as 5,000 aphids in its lifetime. There are generally five to six generations of ladybugs during the growing season.

Costa said there are an estimated 46 genera, including 400 species of lady beetles in North America. While many are native, at least 170 species, like the Asian lady beetle, have been introduced.

Importation of ladybugs is believed to have started in the 1880s when beetles from Australia were introduced in California to save orange groves from the “cottony cushion scale.” While this particular importation appears to have been successful, there are concerns about importing, even beneficial exotics.

“They definitely compete with native species,” Costa said. But to date, there are no definitive studies weighing the pros and cons regarding introduced lady beetles, Costa said.

In fact, there are studies going on now in Connecticut with another Asian lady beetle. Pseudoscymnus tsugae is a tiny (poppy seed size) black lady beetle introduced from Japan where it is known to feed on the hemlock woolly adelgid, also native to Japan.

Hemlock woolly adelgids have infested hemlocks throughout the Appalachians from North Carolina to New England. Scientists say early experiments with P. tsugae show promise, but it’s much too early to tell if this “enforcer” will be the answer to the hemlock pest.

On the plus side, however, this ladybug doesn’t demonstrate the same swarming characteristics as its Asian cousin.

(Don Hendershot can be reached at don@smokymountainnews.com).

 

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