NGA Articles: The Do-Good Bugs

The Do-Good Bugs (cont)

By: Whitney Cranshaw

Lady Beetles (Ladybugs)

The most widely available biological control is the convergent lady beetle, Hippodamia convergens, which feeds on small soft-bodied insects, especially aphids. These lady beetles are field collected rather than reared in insectaries, largely because they aggregate in large masses in the foothills of California and are easily gathered when dormant. Typically, collected lady beetles have not matured eggs and are ready to migrate immediately, dozens of miles away. Releasing them in your garden is fun but does almost no good against a pest outbreak.

Recently one supplier has begun offering convergent lady beetles that it has "preconditioned" by feeding them long enough for eggs to mature. Another advantage to this practice is that parasitized lady beetles can be culled out, slowing the spread of the tiny wasp that kills them. Preconditioned lady beetles will stay in your garden as long as the food supply lasts, eating aphids and laying eggs to produce larvae that also eat aphids.

Coast to coast, convergent lady beetles are a very common native. There are more than a hundred other lady beetle species (some introduced) that feed on aphids, scale and other pests. You can concentrate local populations in your garden by attracting adults. Use the artificial honeydews, such as Pred-Feed, and plant nectar and aphid-host sources, especially alyssum, legumes or flowers in the family Umbelliferae (wild carrot, dill and the like).

Pedio wasp

This small wasp, Pediobius foveolatus, parasitizes Mexican bean beetle larvae. It's native to India, where it attacks a related insect. It cannot survive American winters in the bean beetle's range. Order the pedio wasp early in the season, when you first notice adult bean beetles. By the time it arrives for release, the bean beetle larvae will be starting to hatch. The wasps control bean beetles very succcessfully if introduced early in the season this way. They're more effective than the spined soldier bug, the only other biocontrol for bean beetles.

The Pedio wasp is not widely available and a little expensive. But it is very effective and fascinating to watch, and one release will protect gardens within half a mile.

Predatory Mites

Various species of mites are sold to control spider mites and thrips, especially on greenhouse crops and indoor plantings. Some of them also work on mite or thrips outbreaks on roses, strawberries, fruit trees, cucurbits, eggplant and other garden plants.

Each species has different requirements for temperature and humidity, so discuss your needs with the supplier at the time of ordering. All predatory mites require fairly high humidity (70 percent or more)--their effectiveness may be lower in dry regions. They also prefer to forage on plants without hairy leaves.

Release predatory mites early in the season. Watch carefully for incipient spider mite or thrips populations, then order predatory mites immediately by phone. The mites are perishable and require special shipping, one of the reasons for their high cost, around $20 per 1,000. Your concentrated population of mites will disperse when the food source becomes scarce, so you will need to order more mites if outbreaks occur later in the season. Predatory mites are very susceptible to soap sprays and other insecticides, so use soaps only before the mites arrive.


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