Don’t Tread on These : Beneficial Bugs Terminate Their Pesky Counterparts While Weeding Out Pesticides

See that nasty-looking creature above? If you come across it, back off.

This ruthless killer--the larva form of the convergent lady beetle--is the Arnold Schwarzenegger of the garden. It exterminates up to 400 aphids, whitefly, mealybugs or other undesirables before its transformation into an adult ladybug.

“And to think I’ve been squishing them for years,” sighs Anaheim gardener Dennis Glowniack, who just learned the larvae’s true identity. “Ladybug larvae are something you definitely want in your garden. They eat twice as many pests as the adults.”

If Glowniack, a member of the California Organic Gardening Club and a practitioner of organic gardening methods for nearly 30 years, can make that kind of mistake, imagine what those of us without his experience are doing.

Nick Nisson, an entomologist with the County Agricultural Commission, cites another common example of overkill.

“One beneficial (insect) that people bring in all the time thinking it’s a pest is Cryptolaemus montrouzieri, the mealybug destroyer,” he says.

He describes a typical scenario:

“Norfolk star pine is prone to golden mealybug (a sap-sucking pest), but people don’t usually notice the mealybugs until they start producing enough honeydew to be messy. Then they notice insects crawling on the leaves. At that point what they’re probably seeing is the mealybug destroyer, which (in its larva stage) looks almost like a mealybug, except that it’s larger. That’s when they haul out the chemicals.

“It’s like killing the rescue team.”

The answer to what you should do about most bugs, says Nisson, is nothing.

“If a pest is there in large numbers, be patient and some beneficial will come along and take care of the problem for you,” he says. “Poisons are rarely necessary.”

Attract beneficial insects to your garden ahead of pests by planting lots of pollen and nectar plants, which adults insects use as a supplement to or as their sole diet, suggests John Kabashima, environmental horticultural adviser at the Cooperative Extension. (Many beneficial insects are only predacious during their larvae stage.) And avoid using toxic sprays and dusts.

If you or a garden predecessor have been using a broad spectrum poison which kills good and bad bugs indiscriminately, you may want to import some beneficial insects into your garden to speed up the process of bringing it back into balance.

One of the best predators for the home garden, Kabashima and Nisson agree, is the green lacewing (Chrysopa carnea). Though lacewings have earned the nickname “aphid lions,” they’ll devour any pest without a hard shell including aphids, mealybugs, whitefly, small caterpillars, mites, thrips and immature scale.

Another advantage of lacewings is that, unlike ladybugs, they’re not the roaming kind. One purchase is often all that’s needed to establish a local population.

That has been Glowniack’s experience.

“I bought some lacewings about eight years ago to combat whitefly and mealybugs on my citrus trees and spider mites in my boysenberries, and they’ve been around ever since,” he says.

“They’re very small (less than an inch long), green like plants and have transparent wings. So they’re well camouflaged. But they’re there if you look for them.”

Another good buy in beneficial insects is Encarsia formosa, a minute parasitic wasp that preys on greenhouse whitefly, a sap-sucking pest that causes wilting, yellowing, loss of leaves and a black, sooty fungus in greenhouse plants and, in subtropical climates like Southern California’s, in outdoor plants as well.

E. formosa wasps feed on whitefly larvae and lay their eggs in them. The Encarsia eggs hatch into tiny worms that feed off whitefly larvae and kill it before emerging as adult wasps.

Jean Graham of Irvine testifies to E. formosa’s efficiency in combatting whitefly.

“I had a very bad infestation on my apple tree,” she says. “The honeydew from the whitefly produced a lot of black mold, and the tree looked awful.”

Graham put strips of whitefly parasitic wasp eggs on the branches, as recommended by her local nursery, and, she says, “it cleaned up the tree in two weeks.”

E. formosa does not parasitize all forms of whitefly, however, warns Nick Nisson. Identify your problem before spending your money, he advises.

Ladybugs are undoubtedly the most widely purchased beneficial insects in the country, but in the opinion of many experts they are not the best use of gardening dollars.

“My theory is they tell you to release ladybugs at night, so you can’t watch them fly away,” says Kabashima. “The convergent lady beetle is migratory by nature. No matter what you do, they won’t hang around.”

As long as ladybugs decimate the worst of a crop of pesky pests before they split, who cares?, counter other gardeners.

“I use ladybugs on my roses every year,” says Mary Lou Heard at Heard’s Country Gardens in Westminster. “If they clean out the aphids and then move on, that doesn’t both me. They’ve done their job.”

Fritz Steinbach in Huntington Beach shares that sentiment.

“Someone suggested I put out ladybugs once a month to control whitefly in my fruit trees (apple, apricot, peach, plum, and pear), and that’s what I do,” he says. “I don’t like to spray because I’ve got five cats and two dogs. The ladybugs seem to work. I’ve never had to use chemicals.”

Kabashima recommends releasing ladybugs at night when they’re least active. Also hose the garden down first to make it temptingly moist, he suggests, and place the beetles where you want them to dine. Even better, he says, is putting a mesh bag over the plant and releasing the ladybugs underneath it.

Praying mantis, though popular nursery sellers, are generally considered a poor choice for pest management in the home garden. Sitting and waiting for prey instead of stalking it, they’re dainty eaters. Also they reproduce only one generation a year, and therefore can’t increase in response to growing pest populations like other predators can.

Yet some gardeners swear by them.

“I maintained a population for four years until our association sprayed for wasps, which killed everything,” says Graham. “And I know they helped.”

Besides, praying mantis are fun to watch. These slimy, prehistoric-looking insects grow several inches long--almost big enough to be considered pets--and suppliers claim you can hand feed them insects or pieces of raw meat.

Decollate snails, a corkscrew-shaped mollusk that feeds off common garden snails, are are also recent strong sellers at local nurseries among customers looking to get away from toxic snail powder and pellets. Yet, minus garden snails to feed on, decollate snails munch on greenery, too, authorities warn, and can be pests in their own right.

Are they a good idea? Well, that depends, says Kabashima.

“For shrubs and well-established landscaping, I think they’re fine,” he says. “I use them in my own yard.

“But you might not want to use decollate snails in an area with a lot of seedlings, because a little damage does a lot of harm with small plants.”

Burying a copper screen under your vegetable bed or nailing a strip around a raised border is a better way to control snails, he suggests. Copper is toxic to snails and slugs, and they will not cross a copper barrier, says Kabashima.

If your vegetable patch is plagued by cabbage loopers and tomato hornworms, you might want to consider investing in Trichogramma eggs. Trichogramma are tiny parasitic wasps that lay their eggs on the eggs of more than 200 species of butterflies and moths. The emerging larvae feed on the host eggs, thereby destroying them. They are a highly effective control for leaf-eating caterpillars.

Trichogramma is not very discriminating though. “They deposit their eggs on any caterpillar,” Glowniack says. If most of the butterflies in your garden are welcome visitors, use the microbial insecticide, Bacillus thuringiensis, instead, he suggests. Apply BT sparingly and only on those plants that host pest caterpillars, he advises.

Parasitic nematodes, which feed on cutworms, grubs, weevils and other soil-dwelling insects food crops are susceptible to, are another beneficial vegetable gardeners might consider. Glowniack, tired of seeing his squash seedlings disappear, is experimenting with the microscopic worms for the first time this year.

Using them was a real leap of faith, he says.

“Mine came embedded in a sponge which looked like it had been dipped in blue paint,” Glowniack says.

“You rinse and rinse it in a pail of water, and then you spray the blue water around the plants, and you take it on trust that the 50,000 nematodes they say are in the sponge are really there, because you can’t see a thing.”

But using chemicals is also an act of faith, Heard points out. And, in her experience, chemicals have not always justified her trust:

“The first few years after I opened the nursery I found myself running to chemical suppliers all the time,” she says. “I’d kill one thing, and then a secondary pest would come along and do even more damage, and I’d have to go back and buy something else. I was pulling my hair out, wondering what I was doing wrong. But, the truth is, chemicals are just not the panacea we were lead to believe.”

Heard’s first experiment with beneficial insects was using E. formosa to tackle whitefly. When that worked (“we have had virtually no whitefly here for two years”), she tried lacewings and ladybugs.

Though she hasn’t abandoned chemicals completely, Heard finds herself using them less all the time. “The more I wean myself from chemicals, the stronger the nursery becomes. And, now that things are back in balance, it’s a lot less work.”