Nurturing the beneficial bugs in your garden

By Rebecca Jepsen
for the Mercury News
September 4, 2009

If you cringe when you encounter insects in the garden — or spot their eggs or larvae — it's time to reconsider that reaction. There are many bugs we should learn to love for the great work they do for us. More than 90 percent of garden insects are called "beneficials" because they pollinate plants, improve soil and eat the so-called bad bugs (such as destructive aphids).

Here's a guide to recognizing some beneficial bugs in all their life cycles.

LADYBUGS
A favorite predator that most of us recognize in its adult form is the convergent lady beetle (ladybug). Larvae, like the adult form, have insatiable appetites for aphids, so it is important to identify and preserve all of the stages of its life cycle. Lady beetle larvae are blackish with orange spots; they have long legs and elongated bodies that resemble tiny alligators. Eggs are oblong and yellow and are laid in groups on leaves and stems near concentrated populations of aphids.

LACEWINGS
Green lacewings prey on a wide variety of insects. Adults have four translucent wings, golden eyes and green bodies, and they feed on honeydew, nectar and pollen. The larvae, which look like tiny alligators, are pale with dark markings. They can consume as many as 1,000 aphids per day. They also attack mealybugs, mites, whiteflies and small caterpillars. Eggs are green when laid and darken before hatching.

SYRPHID FLIES
Adult syrphid flies feed on nectar and pollen and are often called hover flies because of their pastime of continually hovering above the flowers. With black-and-yellow bands across their abdomen, they are frequently confused with honeybees; however, syrphid flies do not sting. The whitish-to-gray oblong eggs are laid near or within aphid colonies. The maggot-shaped larvae are the most important aphid predators in all types of gardens.

NOW FOR THE GORY DETAILS
Most beneficial insects are either predators or parasitoids. Predators attack, kill and feed on many other bugs over the course of their lifetime. Parasitoids live in or on a host bug for part of its life cycle and generally kill the unfortunate victim.

MORE FRIENDS OF THE GARDEN
There are several families of parasitoid wasps. The non-stinging wasps lay their eggs on or in the eggs, larvae, pupae or adults of other insects. The emerging larvae become predators of their host. Parasitic wasps have been used to help control aphids, fruit flies, mealybugs, thrips, codling moths and psyllids in both backyard and commercial orchards.

And don't forget about spiders. Because they are extremely capable hunters, some experts consider them to be the most beneficial of all our "creepy-crawlies."

DO'S AND DON'TS
Do introduce to your garden the "insectary" plants that will help attract and retain these and many other beneficial warriors to your garden. Good options that provide nectar and pollen are alyssum, buckwheat, California aster, ceanothus, coreopsis, cosmos, dill, Queen Anne's lace, rudbeckia, sunflowers and yarrow.

Don't use pesticides if you can avoid it. Unfortunately, they kill the good bugs along with the bad. If you must use a pesticide, use one formulated for the specific pest you are going after. Many infestations can be controlled by simply using strong blasts of water from your garden hose to knock down the population.

BUYING BUGS, LEARNING MORE
Many beneficial insects are available for purchase. For tips on necessary preparation and successful release, go to www.rinconvitova.com.

For more information on beneficial insects and photographs to help you identify them, go to www.ipm.ucdavis.edu/PMG/NE/index.html