Beneficial insects are a gardener’s best friend. They break down into two basic groups: predators and parasites. Research shows that some plants, when attacked by an insect pest, actually release chemical signals that lure other insects to prey on the pest. We know the benefits of pollinating bees and the poster good-gal, the lady beetle. How about the other unsung heroes?
Beneficial Predators
These insects attack, feed on or kill pests. They include lady beetles, ground beetles, lacewings, flower flies, robber flies, mantids, assassin bugs, stink bugs, the minute pirate bug, predatory mites and all spiders.
of this group. But many gardeners don’t recognize the larval stage of these two insects; these immature critters gobble aphids, mites and small caterpillars. are about a quarter-inch long and look like tiny black alligators with red or orange markings. are similar, but are light brown and have large hooked jaws at the front.
Flower flies or syrphid flies, harmless to people, are often mistaken for stinging insects, but a closer look reveals a brightly colored orange or yellow and black smooth body with a single pair of wings. The tapered maggot of the flower fly feeds on dozens of small-bodied pests such as cabbage worms and mealybugs. They’re also the first to eat aphids when temperatures are still cool early in the season. before maturation. Adults feed on honeydew (aphid excrement), and are wonderful pollinators.
Spiders — technically arachnids (eight legs) not insects (six legs) — capture prey in webs or by hunting or stalking. They eat caterpillars, leafhoppers, aphids and beetles. There are about 600 spider species in Colorado found in all areas, including the highest elevations. Brown recluses are extremely rare here, but
• Ground beetles are dark brown or black and measure to 2½ inches long. Larvae are wormlike and cream-colored with large, curved jaws in the front of the head. They dine at night on Colorado potato beetles, squash vine borers, tobacco bud worms and many other pests. They hide under rocks, logs or leaf mulch during the day.
PARASITES
Beneficial parasites biologically weaken or kill their prey by living on or infesting another organism with their young.
Adults lay eggs on beetles or caterpillars. These hatch almost immediately, then the young maggots tunnel into their host to feed. Adults are important pollinators and can be found resting on leaves.
Braconid and come in a wide variety of sizes and parasitize 200 species of insects. Their ovipositors (structures for laying eggs) are quite large and easy to mistake for stingers. (caterpillars, flies, scale and many more). The larva feed on the host’s blood and tissue, avoiding killing it until it’s no longer needed.
ATTRACT BENEFICIAL PARASITES
The best way: The good bugs need food, shelter and a place to reproduce. So plant herbs including dill, fennel, mint, lavender and oregano. Plant flowering annuals, perennials, shrubs and more herbs near trees and throughout the yard. More: www.colostate.edu/Depts/CoopExt/ 4DMG/PHC/benefici.htm
LEARN MORE
Books:
Whitney Cranshaw (Fulcrum, 1998); • “Insects and Diseases of Woody Plants of the Central Rockies” by Cranshaw and David Leatherman (University Press of Colorado, 2004); • “Guide to Colorado Insects,” Cranshaw and Boris Kondratieff (Westcliffe, 2006); and • “Good Bug Bad Bug” by Jessica Walliser (St. Lynn’s Press, updated 2011).
Online:
• This page indexes all of CSU Extension’s crop of online bug- information documents: www.cmg.colostate.edu/pubs/Insects.html
• Butterfly gardening info: www.ext.colostate.edu/sam/garden-insects.pdf
