Biological Controls
Researchers have figured out ingenious ways to manipulate natural controls to reduce pests. Some traps use pheromones, the natural perfume that pests use to find each other and mate. Codling moths and peach tree borers can be controlled with pheromone traps. But be cautious about using Japanese beetle pheromone traps. They draw the beetles to the general area but not necessarily into the trap. The result is an increase in Japanese beetles rather than control. The traps can be useful, however, in large yards when they are placed far away from prized plants. Numerous beneficial insects are available commercially at nurseries, by mail and on the Web. But you'll need to persuade these insects to stay in your garden so they don't all fly away shortly after release. Ladybugs, for example, are more apt to stay when you release them in the evening, dispense only a couple per square yard and spray plants with a sugar-water solution to mimic the honeydew secreted by aphids, their favorite taste treat. Another example of beneficial insects are parasites that kill pests by laying eggs inside the pests' body. After the eggs hatch, the larvae eat the pests from the inside out. Not a pretty picture, but it works in the garden. Millions of parasites occur naturally, and you'll find a few available commercially. Most common are tiny wasps called trichogramma. They lay their eggs in moth and butterfly eggs that become plant-chewing caterpillars. These wasps are perfectly harmless to people and animals. Also available commercially are parasitic nematodes that target insects which spend part of their life below ground. Lawn grubs, Japanese beetle larvae and weevil larvae are examples of pests nematodes control. Nematodes work best in loamy soil in mild climates. They are least effective in extremely sandy or clay soils, in dry areas and at extreme temperatures. You'll find them sold in either in a paste form or on a sponge, under such names as Grub-Away and Grub Guard. Mix with water and spray on moistened soil or lawn. Insects, like humans and other animals, get diseases. Some disease-causing organisms are sold to gardeners to target specific pests. Bacillus thuringiensis (B.t., Dipel, MVP), a bacterium that paralyzes the gut only of plant-chewing caterpillars, is one of the most widely available. Another is milky spore, which attacks Japanese beetle larvae but not the adults.
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