Biological control involves discovering, importing and using the most effective natural enemies of pest insects or weeds that can be found. More than 10 million natural enemies of many kinds are released each year by the University of California through its Biological Control Divisions, according to Robert M. Boardman, a UC communications specialist. UC scientists estimate in California alone it has saved more than $300 million in the last half century.

Scientists think about one-tenth of the billions of insects may be beneficial to mankind. Bees, for instance, carry pollen to many of our most important crops. Ladybird beetles feed on aphids (plant lice), which attack many kinds of plants.

In 1975, USDA ARS Beneficial Insects Research Laboratory, in Newark, Del., began introducing into several states the seven-spotted ladybird beetle, the most important aphid predator in Europe, Asia and North Africa. It is now established in several parts of the United States. If sufficient numbers of the beetle can be established widely throughout the country, it should prove a successful biological control for many kinds of aphids, they believe.

Beetles were released in the area of Byron, Ga., in 1976 and in the spring of 1977 were found to be the most abundant aphid predator on the ARS experimental farm's legumes and fruit trees.

In the 1920s, citrophilus mealybug was a spreading scourge in California citrus orchards. It was highly destructive, spread rapidly and affected other fruit trees and ornamentals. The mealybug's origin was a mystery, but UC scientists deduced it must have come from a climate similar to that of southern California.

Finally they decided it came from Sydney, Australia, and a biological control scientist was sent there in 1927.* He collected two different parasites and took them to California. Both were colonized and released in 1928.

A year later mealybugs were already being decimated wherever the parasites had been liberated. Since that time no significant infestations have occurred.

By 1944, Klamath weed, an accidental import from Europe, had taken over 2,000,000 acres of rangeland in 30 California counties, crowding out range grasses. Livestock men suffered financial losses, because cattle and sheep feeding on the toxic weed lost weight.

Prof. Harry Scott Smith, head of biological control work in California, was authorized to import four kinds of beetles and a gall-forming fly from Australia and Europe. These were released and in 1950 more than 3 million beetles were collected for redistribution in California. Beetles also were sent to Washington, Oregon, Idaho, Utah, Nevada and Montana, where they became established.

By 1955, Klamath weed had virtually disappeared as a pest. Land values went up again. As range grasses reappeared, animals stopped losing weight.* UC scientists estimate that savings to the livestock industry plus savings in control costs have been $3,500,000 per year, totaling about $80,500,000 through 1976.

When you prune your shrubs in late winter, watch for praying mantis eggs, and don't harm them. This insect is your friend in the garden, feeding on aphids and other creatures that attack your plants. The mantis lays her eggs in a compact mass covered with a frothy substance.

This soon hardens into a honey-colored object tightly fastened to a twig or something similar. Each mass contains between 75 and 250 eggs that hatch in the spring. If they are on a twig you have removed, tie the twig in a protected spot on the shrub. If you take the egg case indoors, keep it refrigerated until warm weather and then take it back to the garden.