Table of Contents
1: Soil Care Basics | 2: Increasing Humus | 3: Maximizing Cover Crops | 4: Bare Ground and Tillage | 5: Plant Care | 6: Beneficial Insects | 7: Habitat Plantings | 8: Other Strategies for Insects | 9: Yet More Strategies | 10: Gardening All Four Seasons | 11: Eating Fresh
6. Dealing with the Competition: Beneficial Insects
What To Do When the Bad Guys Show Up?
Every gardener experiences at some point the anguish of learning that somebody out there likes his garden produce as much as he does. One day all is well—the garden beds are getting more and more lush and green, and he dreams of meals when almost everything on the plate comes from his own backyard. The next day, there is an invasion by uninvited insect hoards that have gotten to the table first. What to do? He has chosen to be an organic gardener partly because of worries about using toxins in his environment. He wants most of all to avoid introducing poisons into the production of his dinner. But now there is competition for that dinner, and he desperately needs some organically approved way to fight back. He needs an organic way to kill those guys!
We’ve all seen the Mafia movies, right? In the typical movie, the Mafia guys pay the legitimate business owner a visit—someone who owns a restaurant, runs a dry cleaner—and say to him, “Hey, look, you need protection. You really oughta buy some protection.” It’s never quite clear what the business owner is buying protection from. But it becomes increasingly clear that, if the owner submits and buys protection now, he’ll have to pay for it again next month, and the month after that, and the year after that. In other words, it seems that, in buying “protection,” what he is really paying for is the privilege of continuing—to buy protection.
Now what could this odd detour have to do with fighting problem insects in the garden? Let me tell you a little story. I’ve always been an organic gardener. But many years ago, early in our time in Hume, I found Colorado potato beetle to be one of my most difficult insect competitors. And rotenone was my weapon of choice for fighting back. I dusted several times throughout the potato-growing season, managing to keep the exploding population just barely in check.
As my thoughts on the matter evolved, however, I became uneasy about the fact that an insecticide like rotenone—and other plant-derived ones like sabadilla, pyrethrin, and neem—are broad-spectrum in their effects. They are “organically approved” because “they won’t hurt me;” but they are potentially devestating to non-target species like honeybees, lady beetles, preying mantises, and green lacewings. The latter species, I was reading, are potential allies in the fight against problem insects. I had the guilty feeling that I was like a guy in a combat zone—when the enemy attacks, he starts shooting his buddies in his own trench! So one spring, as I was planting the potatoes, I took a Great Vow: I will not use any broad-spectrum insecticides in the garden this year—even if it means losing the crop!
So I was overwhelmed with potato beetles that year, I was overrun, right? Actually, no. I found five—count them, five!—potato beetles on my vines the entire season. Of course, at first I assumed that was just a quirk of the season—any season can be worse or better for a particular insect in a particular crop—I assumed I was just getting the luck of the draw. Until I talked to my neighbor whose garden was right across the road, her potato patch not fifty yards from mine. “My, my,” she wailed, “ain’t these potato bugs just awful! I dust and I dust and I dust—and I’m still out here every day, pickin’ them off by hand!” That was a Zen-like moment of “enlightenment,” a moment of “seeing” the complex, interwoven patterns of life in the insect communities around me. I “saw” as well the arrogance of my assumption that I could blunder into that intricate web and start disrupting one part of it—without tearing apart the fabric of the whole. I “saw” that, as with the business owner buying “protection” from the Mafia, the money I was paying for broad-spectrum insecticides was really buying me the privilege of coming back next year, dollar in hand, for more of the same “solution.”
Dear reader, please know that I am not spinning fairy tales here. I am reporting on my actual experience: In a single season, I received almost total relief from what I had considered one of my worst problem insects—by ceasing to do anything at all. Please allow the significance of that fact to sink in. And note that my “good luck” with Colorado potato beetle was not the phenomenon of a single season only: In every potato season in the seventeen or so years since, I have found potato beetle one of the easiest of all insect competitors to deal with. I simply walk up and down the potato beds once a day for a visual inspection—in other words, I do what every good gardener should be doing anyway: the daily walk-through, seeing how everybody is coming along. If I see the occasional potato beetle, a simple squish! ensures it will not reproduce. But last year, I didn’t find even one, while neighbors were reporting moderate “invasions.”
No, I am not spinning fairy tales—but I’m also not selling pie-in-the-sky. There are competitor insects that have remained more of a problem in my garden—Mexican bean beetle, cabbage worm, and squash bug. With all of them, however, the trend is down: I have less problem with them each year. The following are some of the things I do to help keep them in check.
Probably there was a bit of luck in the amazing results I got with potato beetle that first year I didn’t use broad-spectrum insecticides. I stopped doing anything to kill the potato beetles, but probably in the rush of the season I also allowed some edges of the garden here and there to come up in flowering weeds, which provided needed habitat for beneficial insect species to meet, mate, and reproduce. In every year since then, I have tried to provide better planned and more effective habitat for “the good guys.” I have set aside permanent plots around and in the garden, in which the plantings of habitat plants grow more diverse each year. Not only am I gaining allies against the competitor insects, but my garden becomes more beautiful each year.
My advice to anyone wanting fewer problem insects in her garden without using toxic sprays and dusts? Make it beautiful. Even without knowing more about which plants benefit which insect species, just having a lot of flowering plants around will be a big addition to habitat options for beneficials. But with some thought and research on the subject, you can design plots that do the job even better.
The subject of encouraging beneficial insects is far too broad to examine in detail here. I can only hint at the possibilities.
From the time we were children most of us have loved seeing the colorful lady beetles, like bits of cloisonné jewelry pinned onto a summer day. Who knew that they eat large numbers of aphids, as well as the eggs of other species such as bean beetle? Learn to recognize the larval stage of the lady beetle—not nearly as pretty, but it has an even more voracious appetite for aphids! Another fascinating predator—a true “monster” of the insect world—is preying mantis. Learn to recognize its distinctive tan, foam-like egg case in your shrubs and on dried plant stems in the fall garden; and be careful not to throw them on the compost heap. You can even bring some into the greenhouse for an early start on their season in the spring. Spiders are great allies—both the orb weavers like orange garden spider, ground-dwelling hunters like wolf spiders, and those who lurk on flower heads in wait for prey like crab spiders—all should be respected and encouraged. There are numerous parasitic flies such as those of the syrphid and tachinid groups. Parasitic wasps of the chalcid, trichogramma, and braconid groups (some of them so tiny you might never see one!) help with the control of numerous competitor insects such as cabbageworm, coddling moth, beetle larvae, aphids, caterpillars, tomato hornworm, corn earworm, etc. Ground beetles, big-eyed bugs, and assassin bugs are the gardener’s friends, as are lacewings and dragonflies. The list goes on to include aphid midge, damsel bug, mealybug destroyer, minute pirate bug, parasitic nematodes, predatory mites, predatory thrips, rove beetles, spider mite destroyer, spined soldier bug, tiger beetle, whitefly parasitic wasp, and more. You have friends you haven’t met, never even heard of! Give them all a chance to help out.