Vegetable Gardening (121 page)

Spinosad
is a new biological control agent that has many uses. This soil-dwelling bacteria was discovered in Jamaica as a byproduct in the rum-making industry. It kills a broad range of insects, including caterpillars, thrips, spider mites, and leaf miners, but it isn't harmful to beneficial insects, animals, or pets. However, it is toxic to honey bees so spray it on cloudy days or late in the evening when the bees are less active. Like Bt, the insect must eat the toxin for it to work.

Botanical insecticides:
Botanical insecticides
are derived from plants. The most useful insecticides against vegetable pests are
pyrethrins,
which are derived from the painted daisy,
Chrysanthemum cinerariifolium.
They're broad-spectrum insecticides, which means they kill a wide range of insects. Unfortunately, that means some of the good guys are killed, too. So to avoid killing bees, for example, spray pyrethrins late in the evening. I usually use this pesticide as a last resort. The advantage to using pyrethrins is that it kills pests like aphids and beetles quickly, and has low toxicity to mammals. However, always follow the label and never apply more than is recommended.

The terminology can be confusing.
Pyrethrum
is the ground-up flower of this type of daisy.
Pyrethrins
are the insecticide components of the flower. You also may see insecticides called
pyrethroids,
however. Pyrethroids, such as permethrin and resmethrin, are synthetic compounds that resemble pyrethrins but are more toxic and persistent. They shouldn't be used in organic gardens. Consequently, I avoid pyrethroids.

Home remedies:
Not all pesticides are exotic. Many gardeners have had great success using common household products to control insects in their gardens. One of my favorite home remedies is adding a clove or two of garlic and a few teaspoons of cayenne to a quart of water and then blending it all in a mixer. You then strain the solution to remove the chunks, and using a hand-held sprayer, spray your plants to control insects, such as aphids and whiteflies, and repel animals, such as rabbits and deer. Of course, after it rains, you have to reapply the mix. Commercial insecticide products, such as Hot Pepper Wax and Garlic Barrier, which are based on the common foods, also are available. Either type of product is effective, simple, safe, and fun to try.

Insecticidal soaps:
Derived from the salts of fatty acids,
insecticidal soaps
kill mostly soft-bodied pests like aphids, spider mites, and whiteflies. They also can be effective against Japanese beetles. They work fast, break down quickly, and are nontoxic to humans. Insecticidal soaps are most effective when mixed with soft water because soaps can sometimes burn tender foliage.

Neem oil:
Neem oil
is extracted from the seed of the tropical neem tree. It has been used for centuries in India as an insecticide, to kill parasites in cattle, and even as a toothpaste for humans. Needless to say, it's very safe (except to unlucky pests). Home gardeners can purchase neem oil to repel and kill insects including aphids, whiteflies, leaf miners, caterpillars, and many others.

Summer or horticultural oil:
When sprayed on a plant, this highly refined oil smothers insect pests and their eggs. The words "highly refined" mean that the sulfur and other components of the oil that damage the plant are removed. This oil is relatively nontoxic and short lived. Use it to control aphids, mites, thrips, and certain caterpillars.

Make sure that you don't confuse summer oil with dormant oil. Dormant oil should be applied to leafless trees and shrubs during the winter. It isn't meant to be used on vegetables.

Double-check the oil's product label to make sure that you can use the oil on plants during the growing season. Then follow the mixing instructions carefully. Water your plants before and after applying the oil. But don't apply the oil if temperatures are likely to rise above 85 degrees Fahrenheit. When it's that hot, the oil can damage plant leaves.

Even organic pesticides that have relatively low impact on your garden environment can be dangerous to use as well as toxic to humans; this is true of several commonly used botanical insecticides, such as pyrethrin and rotenone.
Rotenone
is a botanical pesticide that was used heavily in the early days of organic growing, but now has lost favor with many gardeners because of research showing a potential link to cancer and Parkinson's disease. I don't recommend it.

Always follow the instructions on the product label exactly; in fact, not following these instructions is against the law. Also, wear gloves when mixing and spraying pesticides, and spray when the wind is calm. Store the chemicals in properly labeled containers well out of the reach of children (a locked cabinet is best). Dispose of empty containers as described on the label, or contact your local waste disposal company for appropriate disposal sites.

Gardening to Eliminate Diseases