Integrated pest management, or IPM, uses a variety of common-sense, low-toxic methods to control unwanted insects on plants in the garden. One method uses beneficial insects to thwart harmful ones. For example, spider mites are harmful to many plants, but certain predatory mites prey on the undesirable ones. By identifying the destructive pests you have in your garden, you can use their natural enemies to protect your plants.
Examples of Beneficial Insects
Mealybugs are white cotton-like, sucking insects whose natural enemy is Cryptolaemus montrouzieri. Sometimes called crypts, these mealybug destroyers pierce a mealybug's body and suck out its juices.
Scale insects are sucking insects too, and the sugary substance called honeydew that they excrete may give leaves a shiny look. Scale insects look like tiny beige bumps or turtles without legs and appear on the undersides of leaves and along the stems. Use parasitic wasps to effectively control scale insects.
The praying mantis will eat any insect, including another praying mantis. Assassin bugs are handy for consuming caterpillars, including aggravating types of bud worms. Predatory wasps will take out white grubs.
Lady beetles, or ladybugs, are the aphid's natural enemy. If lady beetles don't find enough aphids on a plant, they won't lay eggs there. Ladybug larvae are even more voracious consumers of aphids than the adult beetles.
Identify the Bad Pests
Because more insects are helpful than harmful, it's wise to make sure you can identify an insect as a pest before you destroy it. If you're not able to identify the destructive insects you have in your garden, collect a sample of them, place them in a small glass jar or similar container and take it to your local extension office. They can help you identify the pests and offer information on natural predators and possible chemical treatments you can use to get rid of them if necessary.
Attracting Beneficial Insects to Your Garden
Getting beneficial bugs to call your garden home is fairly easy. Provide them with a source of water, such as a shallow container filled with stones, which gives the bugs a place to land and drink without drowning. A hedge or windbreak of some kind is a good idea too because most bugs don't like extremely windy or dusty conditions. A few pollen-producing plants, especially herbs, scattered throughout the garden will also attract beneficials. Yet the easiest way to introduce good bugs to a garden is to buy them, and they're available at garden centers or online.
Make sure to delay the release of good bugs until plenty of bad bugs are present. Without an adequate food supply, beneficials will quickly leave in search of a more promising habitat. Try releasing bugs inside some sort of temporary enclosure, such as a row cover or other covering over a grouping of infested plants, to give them time to adjust to their new surroundings. Keep the area moist, and let them go within a couple of days.
Avoid using electric bug zappers around the garden. They kill bad bugs, but they also slay the bugs that can help your garden. If you don't want to stop using a bug zapper, try turning it on only while you're out in the garden.