The vegetable garden is planted and growing well, and you are starting to scout for insect pests. While you’re scouting for pests, scout for beneficial insects too.
Many people think all insects are bad, but the truth is, less than 1 percent of insects are pests. Most insects don’t harm the vegetable garden, and some are actually beneficial. These beneficial insects, also called natural enemies, are the free workforce in your vegetable garden. They are those insects that prey on insect pest species.
A common beneficial insect most people recognize is the ladybird beetle, more commonly known as the ladybug. Unfortunately, many people don’t recognize the larval stage of the ladybird beetle: ½-inch long, alligator-like in shape, colored black with spines and brightly colored spots. Both the adult and larval stages prey on aphids, scale, mealybugs and mites. One larva may eat 200 to 500 aphids before becoming an adult, and adult ladybird beetles may consume up to 5,000 aphids in their lifetime.
Another common beneficial insect is the green lacewing. This delicate, ¾-inch long, green insect with four see-through, lacy wings produces tiny, pale brown with darker brown markings, ½-inch long, alligator-shaped larvae. The larvae have distinctive, curved mandibles (jaws) for attacking prey. The larvae are voracious, consuming mealybugs, thrips, mites, whiteflies, aphids, small caterpillars, leaf hoppers and insect eggs. These insects can have five to six generations a year. Most of the adults feed on nectar and pollen, but a few species feed on insects. The adults are attracted to goldenrod, dandelions, yarrow and wild carrot. They are also attracted to bright lights at night. Providing water and the flowers they prefer can help keep the adults in your landscape, providing additional larvae for your pest-control workforce.
A relative of the green lacewing, the snakefly is another common beneficial insect in our area. The adult insect has four see-through wings, like the green lacewing, but the body is colored dark brown to almost black. Additionally, the middle body section in the adult is elongated so that the head can be raised above the rest of the body. This gives the adult the appearance of a snake ready to strike, hence the name snakefly. The larva is ½- to 1-inch long and flattened, with a black shiny head and three pairs of legs. Both adults and larvae are predators, consuming aphids, caterpillars, insect eggs and some wood-boring insect pests.
As you inspect your garden for insect pests, you should also note the beneficial insects present. It’s important to remember that there is a lag time between when the insect pests arrive and when their predators show up. Sometimes you need to wait a week or two for the beneficial insects to show up. These beneficial insects will be killed along with insect pests if you elect to spray an insecticide, a pesticide that kills insects. Use insecticides thoughtfully. Remember: if you kill the beneficial insects, you inherit their job.
Want to learn more about beneficial insects? Go to http://www.unce.unr.edu/programs/sites/ipm/gallery/insects/beneficial/ for photos and more information on beneficial insects in our area.
Melody Hefner is the Urban IPM and Pesticide Safety Program coordinator for University of Nevada Cooperative Extension. Have a gardening question? Contact a master gardener at firstname.lastname@example.org.