Wildlife Center of Silicon Valley

Out of about a million species of insects, less than 3% are considered pests by humans. Yet insects remain greatly undervalued! Some people lump all insects together and consider them just plain creepy. The mere sight of some insects sends people running off to get spray cans of pesticides and insecticides. Learn to recognize and value the good garden bugs for the necessary roles they play in keeping our gardens healthy. Keep the bad bugs in check by working with the beneficial insects in creating a well-balanced vibrant garden.

Know Your Allies & Your Enemies

Ladybug: Everyone recognizes the familiar ladybug, also called ladybird beetle. Many species have enormous appetites for aphids—one of the most common plant pests. Others prefer scale insects and mites and are quite effective in reducing infestations. While adult ladybird beetles do eat aphids, the immature beetle is even more beneficial. The immature beetles look like tiny alligators and are often marked with orange or yellow spots. They don’t look anything like the adults that they will become! The immature beetles feed on aphids, scale insects, mites, mealy bugs, whiteflies, thrips, and the eggs of other insects.

Honey Bee: Perhaps the best known and recognized pollinator, and our best insect friend. Besides pollinating services, these insects provide honey for eating and beeswax, which is used in candles, polishes, inks and numerous cosmetics. We can imagine a very different life without the natural pest control, flower pollination, and products provided by honey bees.

Syrphid (or Hover) Fly: Hover flies are often mistaken for bees or wasps because they have similar yellow and black markings. Hover flies cannot sting. Adults are pollinators, but the immature maggots are predators. They are pale, greenish brown and eat aphids, leafhoppers, scale insects, mealybugs, thrips, corn borers or corn earworms. One hover fly maggot will eat 400 aphids!

Ground Beetle: There are hundreds of kinds of ground beetles, and most eat other insects. Both adults and immature ground beetles are predators – they will feed on caterpillars, cutworms, root maggots, spiders, snails, slugs, mites and other beetles. Very common under logs and debris, this is another friend of humanity.

Dragonfly: They are relatively large and colorful, associated with water during every stage of their life, and are especially valuable because they eat mosquito larvae and adults. Dragonflies will not bite or sting humans, but they are voracious predators of small insects, including midges, mosquitoes, small moths, bees, butterflies or other dragonflies.

Parasitic Wasp: Most are tiny and don’t sting. They live inside small insects or even inside insect eggs, and eat their host as they are living inside them. When the adult emerges, it kills its host. Some of these wasps are so small that you probably wouldn’t recognize them as wasps. They destroy the eggs of cabbage loopers, cutworms, tomato hornworm, aphids, scale, mealybugs, armyworm, gypsy moth, alfalfa caterpillars, and spruce budworm.

Rallying the Troops

Tips to attract predatory insects to your garden to help out with pest control:

• Don’t use pesticides. Pesticides rid your garden of many beneficial insects which are necessary for a healthy garden. Instead, attract predatory insects and other animals, such as birds, into your garden and make them welcome with a favorable habitat. Then let them control any pesky bugs. Even organic pesticides can Plant a variety of flowering plants, especially ones with small flowers rich in nectar. Although many insect larvae are predators, a diversity of flowering plants will supply the nectar and pollen necessary to many of the adult forms, as well as provide safe places for resting and laying eggs.
• Intercrop. Mix up your plants so those that attract beneficial insects are nearby those that need protection.
• Place your plants in the ground, or in tubs and pots, close together to provide a moist, shaded environment for beneficial insects who dehydrate easily.
• Provide a source of water for beneficial insects by putting out a shallow dish of water with stones to allow them dry places to land.
• Plant ground covers to provide shadowy, sheltered spots for spiders (they are also our friends in the garden).
• Keep your soil healthy by adding compost to allow soil organisms to thrive.
• Attract beneficial insects to your yard rather than buying and releasing them. Releasing insects may rid your yard of naturally occurring beneficials through competition and predation (some beneficial insects, such as praying mantises, feed on both pests and other beneficial insects). In addition, some insects, such as certain ladybugs, are migratory and, once released, they quickly move on to other locations.

Resources: Lana R. Adams’ publications, PennState College of Agricultural Sciences Cooperative Extension, Frankly County Office.