Lady beetles and other insects feed on these rapidly reproducing threats to foliage

When large numbers of aphids suddenly appear on succulent spring growth, you may wonder how they got there. Aphid survival depends on rapid reproduction, and they accomplish this with cloning. When a winged female lands on new foliage, she soon gives birth to lots of wingless females that are born live and pregnant. Her offspring quickly mature and produce more females without mating. This may continue until the population is too dense or the environment is unfavorable. Then winged aphids are produced that disperse to other sites.

Dense aphid populations are often controlled by natural enemies, including green lacewing and syrphid fly larvae, lady beetles and their alligator-shaped larvae, soldier beetles and mini-wasps. Visit the “Natural Enemies Gallery” at for photos and more information. Protect beneficial insects by not spraying plants with broad-spectrum insecticides that leave persistent toxic residue on foliage. Aphids can be washed off plants with a forceful spray of water. If a pesticide is necessary, use less-toxic products like insecticidal soaps or horticultural oils. Also, control ants that protect aphids on plants to help natural enemies do their job.

Q: There are lots of aphids on my roses. If I buy ladybugs to release, will they get rid of the aphids?

A: Lady beetles, also called ladybugs, feed on aphids, but releasing a small container of these beneficial insects in your garden may not get rid of all the aphids on your roses. University of California research shows that large numbers of purchased lady beetles are required to control aphids on garden plants. Most packages sold in stores only contain enough lady beetles to treat one aphid-infested shrub or a few small plants.

The effectiveness of releasing lady beetles depends on the number released and how well the insects are handled before and after you purchase them. Here are a few tips:

• Buy fresh lady beetles. Check how many insects are alive before you buy the container.

• Lady beetles should be refrigerated at a retail store and at home until you release them. Beetles left out at room temperature rapidly deteriorate.

• Keep refrigerated lady beetles hydrated by misting them with a little water about once a week. Use a squirt bottle and do not allow water to puddle in the container.

• Release lady beetles soon after buying them, at dusk or early evening. They fly away almost immediately if released during the heat of the day or when the sun is shining.

• Spray plants with a fine mist of water before lady beetles are released to keep them around longer.

• Place beetles at the base of plants or in crotches of low branches. They will crawl up the plant in search of aphids.

Lady beetles offered for sale naturally want to disperse. Even when released with care, most fly away in a few days.



