Gardens February 2001

It’s a Bug-Eat-Bug World

Biocontrols are the newest old thing in gardening

For $31.87 plus shipping Mike Cherim, the proprietor of The Green Spot, in Nottingham, New Hampshire, will sell you a plastic bottle, about the size of a single-serving juice container, into which are tucked 500 minuscule parasitic wasps. These are Aphidius matricariae, which have, in essence, evolved over millennia to rid your garden or greenhouse of aphids. In my garden aphids suck the vital fluids from roses, mock oranges, astilbes, and foxgloves, among other plants, often introducing one or another disease in the bargain. I could control these bugs by spraying them with a stiff chemical cocktail, but I choose not to, because my garden is also populated by birds and bees and butterflies, not to mention two children and a dog, all of which I'm fond of.

Although I do not strictly observe the commandments of organic gardening (I think nothing of sprinkling 5-10-5 on my borders), I prefer natural solutions to pest and disease problems. The tiny parasitic wasps (they're about a tenth of an inch long) are a perfect example. They work like many other parasitoids in the world of biological control, by laying eggs in the abdomens of their hosts, in this case the aphids. The developing larvae devour the aphids' insides as they grow. Once the predator population has wiped out the pest population—and thus its own source of sustenance—it, too, often dies off, in a neat bit of natural symmetry.

I first encountered Mike Cherim and the parasitic wasps in The Green Methods Manual, Cherim's privately published book on biological controls. Biocontrols, as they're known, work on the simple principle of fighting fire with fire—pitting a pest's natural enemies against it. Virtually every insect pest has at least one natural predator or parasite or disease whose existence depends on killing insects of that specific kind.

Biocontrols are part of a larger approach to plant care that is called integrated pest management. IPM promotes the use of biocontrols in combination with a range of other low-impact measures such as mulching (to discourage weeds and avoid herbicides), trapping (of, say, apple maggots or slugs), hand-picking (sometimes disgusting, but very effective), and exclusion (with netting and banding). And although there is sharp debate on the topic, many IPM practitioners accept a limited range of chemical sprays in cases of extreme hardship—such as when you return from vacation to discover that the Japanese beetles are holding their annual get-together at your place.

The increasing interest in biocontrols is by no means revolutionary—indeed, little in the world of gardening is brand-new. It more closely represents a return to tactics that have been in use since at least 324 B.C. That's when the first known account appeared of Chinese farmers' deploying ants in their citrus orchards to control caterpillars and beetles. In this country biological controls originally made their mark in 1889, when the introduction of 500 ladybugs saved that year's California citrus crop—and with it the state's citrus industry—from the cottony-cushion scale.

Biocontrol methods gained international attention and credibility in the 1970s and 1980s, when a parasitic wasp brought to a halt a mealybug that was destroying the African cassava crop and was spreading across the continent at a rate of a hundred miles a year. Recently in this country authorities began testing two possible biocontrols to combat the woolly adelgid, an insect that has been killing hemlocks throughout the East: a ladybug from Japan, which does its work the old-fashioned way (by eating large quantities of the adelgid), and a fungus that uses enzymes to penetrate the skin of the adelgid and eventually eats the thing from the inside out. Demand for beneficial insects of various kinds seems certain to increase, because some pests are growing resistant to chemicals: roughly 450 of them, called superbugs, have developed high levels of resistance to a wide range of pesticides. Increasing resistance requires a constant escalation in the toxicity of the chemicals—a worrisome trend.

None of this is to say that beneficial bugs and other biocontrols are always successful or trouble-free. Every "product" description in The Green Methods Manual includes a "drawbacks" section. The drawbacks range from the flightiness of ladybugs, which are apt to wander off en masse if not properly acclimated, to the aggressiveness of green-lacewing larvae, nocturnal predators that, Cherim reports, "can deliver a painful little bite (to people and each other)."

The Green Spot also publishes a catalogue (available free by calling 603-942-8925; The Green Methods Manual sells for $9.95) that's an A to Z—aphid to whitefly, to be more precise—of good bugs and other environmentally agreeable remedies for everything from Mexican bean beetles and Japanese beetles to leaf miners and various soil pests. There is even a product—a mixture of three species of mini-wasps—for controlling flies around farms, kennels, dairies, and the like. As Cherim matter-of-factly puts it, "Fly management is something we deal in." Then again, it turns out that certain flies are very effective as pollinators, and Green Spot offerings include houseflies (in pupal form) for this purpose, along with orchard mason bees and two species of bumblebees. All in all, it's an unlikely cornucopia of natural goodness.

Cherim's writings in the manual and the catalogue provide a great deal of clear and detailed scientific discussion of the life cycles and interactions of pests and controls. But what particularly captured my attention was the zany streak that runs through his commentaries. The first time I looked at the catalogue, I happened to stumble on his discussion of Neoseiulus fallacis, the all-purpose predatory mite. It begins with glowing praise for this voracious, pinprick-size predator, and goes on to say that unfortunately, the "producer of this product decided the high-pressure demand was too much to bear ... he quit." Cherim continues, "He is now hanging from his fingernails in our storeroom in hopes that he'll soon change his mind." Elsewhere I was taken by the candid sales pitch for a mini-scope (for scouting for bugs), which ends with the comment "Please note: no longer included is the cheesy vinyl carrying case that used to come with it."

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