Teague: Use good bugs at the right time

FresnoJuly 19, 2013 

Beneficial insects are often cited as one of the most effective controls for pest insect populations. Home gardeners are encouraged to plant host plants that attract and harbor beneficials and to refrain from applying broad spectrum insecticides with long-term residual effects that kill off all insects, pest and beneficial as well as pollinators (butterflies and bees). In the last few years, beneficial insects have become increasingly available commercially. Several companies (website addresses are listed below) also ship beneficial insects, eggs, egg sacs and larvae. Before you buy beneficial insects to control for pest insects, you'll need to know the right time for release or application. Weather, season, hatch times, and availability of food (pest insects) are critical for successfully establishing colonies of beneficial insects.

The most commonly purchased beneficial insects are:

Lady beetles: Both the larvae and the adult lady beetle eat 50 to 60 aphids a day as well as whiteflies. But, on average, only 5% of the lady beetles released remain in the release area. The other lady beetles fly off to find homes elsewhere. In our hot summer climate, most lady beetles fly into the foothills to escape the heat.

Buy and release lady beetles in spring when aphid populations are high and when temperatures will remain warm, not hot, for six weeks.

Green lacewings: Lacewings are voracious predators of many soft-bodied insects including mealybugs, spider mites, caterpillar eggs, thrips, whiteflies and leaf hopper nymphs. The eggs are shipped, packed in rice hulls and then sprinkled onto plants. It may take several successive applications for lacewing populations to become established.

Lacewing adults can tolerate high summer temperatures, but the eggs and larvae survive best in warm spring weather.

Beneficial nematodes: These tiny worms burrow into the soft bodies of grubs and larvae (cutworms, hoplia beetles) that overwinter in lawns or just under the soil surface. They are shipped in fall and can be kept for a short time in the refrigerator until applied mixed with water.

My little box of nematodes arrived in early October when temperatures were over 100 degrees and they all fried when left in the mailbox for several hours. Have nematodes shipped to an office or address where they can be brought inside immediately.

Praying mantis: Mantis are fascinating insects that aggressively attack most anything that moves into their territory. Mantis lay their egg sacs or cases in fall to overwinter and the nymphs hatch in spring. One egg case produces 50 to 200 nymphs. Buy egg cases in fall to place into a sheltered spot in the garden or in spring when temperatures warm.

When ordering, specify delivery weeks and follow directions for release or application carefully.

Companies that ship beneficial insects include gardeners.com, planetnatural.com, gardensalive.com and gardeningzone.com.


Elinor Teague is a Fresno County master gardener. Send her plant questions at etgrow@comcast.net or features@fresnobee.com ("plants" in the subject line).

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