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Ecology Blog It’s A Bug’s Life Myth: Pesticides only kill bad bugs Myth Explored Whether it’s stem borers in the roses, caterpillars in the tomatoes or an inconvenient wasp’s nest located directly over your back door, insects can take a lot of the joy out of your little corner of the Great Outdoors. They can stunt your plants or kill them outright. They can devour your fruits and vegetables. The wasps may sting careless kids and curious dogs. The mosquitoes will bite everybody, curious or not. It’s only natural that home gardeners would turn to pesticides to gain a little relief. Unfortunately, pesticides come with problems of their own. Some are so dangerous that it requires a special license to use them at all. Most are more dangerous than you might suspect. A wise gardener pays close attention to the details, reads the labels and follows the directions to the letter. Playing with pesticides is a dangerous game. Let’s learn a few of the rules…. The Situation Follow I-90 east out of Seattle and you'll be startled by the abrupt transition between the coastal forests and the high desert. The Cascade Mountains trap much of the rain and leave vast swathes of the interior too dry for agriculture. By the time you pull into Yakima, with its irrigated apple orchards, it feels like you've discovered an oasis. But be prepared to roll up your windows when the crop dusters come by. Even here, in this island in the desert, the bugs have found their way to the food supply. No matter where you are, and no matter what you’re trying to grow, it will be only a matter of time before the pests show up. Sometimes the damage they do is tolerable. But sometimes the infestation is so bad that pesticides seem to be your only option. Let’s talk about that. The Problem Humans have been battling bugs for a very long time, and we’ve come up thousands of solutions. But in general, pesticides fit into three broad categories. Some pesticides are designed to be “systemic,” meaning that the plants draw the appropriate chemicals up through their roots and render the entire plant toxic to attacking insects. Others kill through direct contact with the insect’s body. Bacteriological pesticides like BT (Bacillus thuringiensis) work by introducing bacteria that secrete toxins after they’ve been ingested by the insects. Even “organic” farmers deploy pesticides. They won’t use artificial chemicals or systemics, but if an infestation gets bad enough they’ll spray BT or natural contact-killers like the chrysanthemum-based pyrethrum, which breaks down quickly in the environment and won’t be absorbed by the plant through its root system. Note that while pyrethrum is light years better than DDT, it’s still a nerve toxin, and very dangerous to humans and animals when it’s being applied. Bottom line, pesticides are poisons. Even if the current research indicates that a particular pesticide seems to be harmless to humans, who really wants to be the guinea pig? Furthermore, not all of the bugs in your garden are your enemies. Insects like ladybugs, lacewings, and praying mantids are actually your allies. They make their living gobbling up your garden pests. Others, like bees and butterflies, are pollinators. Many of your plants can’t get along without them. And some bugs are just fun to have around, like the lightning bugs that entertain the kids on a summer evening. (Lightning bug larvae are also useful predators.) Pesticides will kill good bugs right along with the bad. The same systemic pesticide that defends your flowers from aphids will also poison the bees and the other pollinators when they eat the pollen and the nectar. A knock-down spray that gets rid of grubs and caterpillars will also kill your ladybugs and lacewings. And by killing good bugs along with the bad, pesticides throw your whole backyard ecosystem out of whack. As the poison degrades and the insects return, it will be the pests who arrive first, looking for their food supply. The predators will follow, but probably not before the pests have already had their fun. So, having used the pesticide once, you may find that you’ll have to do it again and again. The Solution Consider pesticides; any pesticide, to be a weapon of the last resort. It’s natural to have a few bugs nibbling on your plants, and there’s no need to panic as long as their natural predators seem to be keeping things from getting out of hand. The discovery of one caterpillar in a row of healthy tomato plants is probably not a portent of doom. It’s not yet time to reach for the heavy artillery. Design your garden to be attractive to natural predators. Many predators supplement their diets with pollen and nectar, so they like a garden that blooms all summer. Planting a variety of flowers alongside those home-grown tomatoes doesn’t just make your garden prettier; it helps defend it from insect attack. When you do think you have a serious infestation, don’t act until you’ve done your homework. Examine your plant closely, figure out what the pest is, and research the available solutions. You may find that you can control your particular problem with relatively non-toxic measures, like insecticidal soaps or vegetable-based horticultural oils. (Some plants can be damaged by the soaps and oils, but many won’t mind them a bit. Read the label.) Even if you do decide that a pesticide is the only option, be aware that pesticides are not all alike. They all pose different levels of risk to you and to your backyard environment. They will be labeled accordingly. “Caution,” means the product is considered to be reasonably safe, so far as anybody knows. “Warning” means the stuff has known toxicity issues. “Danger” means that you’ll definitely get yourself, your children or your pets into serious trouble if you make a mistake. If a product with low toxicity will solve your problem, why take chances with anything uglier? No matter what pesticide you use, follow the directions to the letter. What You Can Do Read the label every time you handle a pesticide. Read the whole thing. Buy only the amount of pesticide you need for the project at hand. Why keep poisons in storage? Leave pesticides in their original containers until you use them, and keep them locked away where pets and children can’t get at them. Know the signs of pesticide poisoning, and learn the first aid instructions – backwards and forwards -- before using the product. If you’ve got old pesticides stashed away they may not even be legal anymore. Read the label, and if necessary, dispose of them properly. Wear protective clothing when using pesticides. Don’t smoke, don’t eat, don’t drink – don’t get the stuff into your mouth. Don’t use a pesticide on a windy day, when you can’t control where it’s going. Pay strict attention to what the label says about the amount of time needed before a treated area is considered to be safe for humans, pets or wildlife. Resources United States EPA: About Pesticides http://www.epa.gov/pesticides/about/index.htm University of Illinois: Alternative Methods for Insect Management http://web.aces.uiuc.edu/vista/pdf_pubs/altinsec.pdf
Cornell University: Biological Controls for
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