The Do-Good Bugs (cont)
By: Whitney Cranshaw
The Home Gardener's Top Beneficials
There are about 50 "good bugs" raised and sold commercially today. Many are very specific to regional or agricultural pests. Some are expensive or only available in limited quantities. Others, such as the praying mantis, are common but of limited usefulness. Those listed here are widely useful and available.
Encarsia formosa This small wasp that parasitizes the greenhouse whitefly has a long history of success in greenhouses. It can work almost as well outdoors when greenhouse whitefly attacks tomatoes or other plants. But Encarsia is not particularly well adapted to control sweetpotato whitefly. It will naturalize only where greenhouse whitefly is found year-round, essentially places that are completely frost-free.
Order this parasite as soon as you notice a whitefly population building. Good control occurs, however, only when minimum average temperatures are at least 72°F (for example, 62°F at night and 82°F or more in the day). At those temperatures, the Encarsia wasp can develop as fast or faster than the whitefly population. Insecticidal soaps and horticultural oils that you might also use on whiteflies don't harm the wasps seriously. Two releases one to two weeks apart will last the whole season.
Lacewing larvae are voracious. They are sometimes called aphid lions, but will eat just about anything they can subdue, including thrips and small caterpillars. Lacewings are most commonly sold as eggs, mixed with a carrier like bran or rice hulls. You can also buy the larvae. They cost about 10 times as much as the eggs but may be a good value, given that ants and other predators often eat a great portion of lacewing eggs.
Purchased eggs or larvae are best used as a biological insecticide--sprinkle them near a serious outbreak of a pest. The larvae will feed in the area as long as there is plenty of prey, and then your lacewing population will disperse.
There is little point in buying adult lacewings. It's more economical to attract one of the dozens of species native to North America. No matter where you live, there should be wild lacewings nearby, though not in as dense a concentration as you get when you release 500 or more eggs from a supplier. The adults of most species feed on nectar and honeydew produced by aphids and other sucking insects like leafhoppers, whiteflies and mealybugs. You can build up the population of wild lacewings (and help keep the adults that hatch from the eggs and larvae you release) in your garden by applying a sugar and protein mixture that simulates this honeydew. Dribble it onto the foliage near your garden, and especially near a pest outbreak. Commercial preparations of these insect foods have names like Pred-Feed and Bug-Chow.