Gardeners know aphids as tiny, squishy pests that can suck the life right out of plants and, as if that weren't enough, leave behind a sticky, nasty mess.

That's why it's surprising to hear a nursery owner embrace the soft-bodied insects. Roberta Churchin, co-owner of Shades of Green Nursery on Sunset Road, appreciates their role in the good-bug, bad-bug drama that plays out among the stems and leaves.

"Aphids are a primary food source for beneficial insects," Churchin says, and those good bugs are important to controlling other insects that damage plants.

Ladybugs and their alien-looking larvae eat aphids. So do assassin bugs, which sound vicious but also chomp mosquitoes, large beetles and their grubs, according to Malcolm Beck and Howard Garrett's Texas Bug Book ($29.95 University of Texas Press). In their larval stage, lacewings - one of the prettiest insects in the garden - eat hundreds of aphids a day. The larvae, sometimes called aphid lions, also have a taste for damaging whiteflies, cabbage loopers, mealybugs and some beetles and their larvae.

Aphids get partial credit for Churchin's switch to a chemical-free nursery environment about 20 years ago. She had noticed lacewing larvae on a mandevilla stem covered with aphids and left them so they could be photographed for a TV segment. The next morning, the aphids were gone.

"We realized we didn't have to spray anymore," Churchin says. Insects, like bacteria, adapt, mutate and become resistant to sprays, she explains. "But they can't get resistant to beneficial insects."

Aphids, which feed on tender new growth, are tenacious, but they can be controlled with a strong blast from the water hose or by releasing ladybugs.

Spray the affected plant with water before releasing ladybugs; these little beetles need water. The adults will eat some aphids, but even more will be eaten by their larva.

A bag of about 2,000 ladybugs costs $12 at nurseries. Churchin says the insects might seek out food sources in a neighbor's yard when they've eaten the aphids in your garden. "They may fly away, but they don't go away," she said.

Churchin plants aphid-attracting butterfly weed and gaura to lure beneficial insects to her garden. Watching the food chain in action, she says, is fascinating.

"Ladybugs are cute, efficient and nontoxic. And they go a long way toward a balanced environment."

Beck also explains how good triumphs over bad in Texas Bug Book. Balance is the goal, he writes. Sustaining nature's great system, he adds, "requires an overall organic program of providing what is needed when it is needed."

That balance might begin with a few aphids.