When you want to buy something to control aphids, wasps or powdery mildew in your garden, you're probably looking for the safest, most effective product. At the garden center, you're likely to find all sorts of products labeled "organic" and "natural," which implies that these products are safe.
Don't be fooled. Pesticides -- which are by definition poisons -- aren't transformed into safe, environmentally friendly products just because they are organic or natural. As with synthetic pesticides, many organic pesticides pose significant dangers.
Trust the label, not the hype
A quick way to assess the relative danger of any pesticide is to read the label. There, you'll find what's called a signal word. The safest pesticides tend to be those labeled with the word "Caution." Those that are less safe are labeled "Warning." And those labeled "Danger" are likely to be the least safe.
Some of the most dangerous organic pesticides include Rotenone, a plant-derived insecticide. (Though it's no longer being produced as an insecticide because of its toxicity to humans and the environment, it's still available in garden centers.) Another dangerous organic pesticide is Bordeaux mix, which contains copper sulfate, which is a dangerous poison to fish and other aquatic creatures. Ironically, both of these ingredients are among the most effective, naturally occurring poisons.
Even organic pesticides derived from foods may not be entirely safe. Capsaicin, the chemical that makes hot peppers hot, is sometimes sold as an insecticide. Capsaicin also is used to make pepper sprays that are sold to repel muggers. If misapplied, you can bet that it'll sting a gardener's eyes as much as a carjacker's.
How to grow organic
The real mission of organic gardening has nothing to do with pesticides: It's about growing plants so they don't need to be slathered in poisonous goo in the first place.
So, how can you do that?
• Start by growing the healthiest plants possible.
• Use renewable, natural fertilizers such as compost and fish emulsions, which enrich the soil and give the plants the nutrients they need to grow and prosper.
• Add mulch to suppress weeds.
• Pests love water-stressed plants, so be sure to water properly. Keep the soil around your plants slightly moist, but not wet.
• Finally, select disease- and insect-resistant plants, which are usually well-advertised as such.
Assess the real damage
But what happens when, despite all of your efforts, you get pests in your garden? Before you reach for the chemicals, consider these questions:
• How bad is the problem? Most plants tolerate losing about one-third of their foliage before they really suffer.
• Is the fruit being affected? If you're growing fruits or veggies and something is eating the leaves but leaving the fruit alone, you don't necessarily need to apply chemicals. Your harvest may not be affected.
• Do you know exactly which pest is attacking your plants? If not, don't apply a pesticide. You're as likely to apply something that hurts the plant as something that helps it.
If you want help identifying a pest, go to the University of Minnesota Extension Service (www.extension.umn.edu), click on garden and look for insect and disease listings under flowers, fruit, lawns or trees and shrubs.
• And finally, if you decide to use a chemical, read the label thoroughly and be certain that what you're applying is the safest product you can find. Remember, while the organic label indicates that something is natural, it has nothing to do with how safe or effective it is.
Jeff Gillman is an associate professor of horticulture at the University of Minnesota. He's also the author of two books, "The Truth about Garden Remedies" and "The Truth About Organic Gardening," (Timber Press, $12.95).