When an insect pest moves into your garden, there are alternative methods of controlling it rather than reaching for the insecticide. Integrated pest control management calls for deciding what population levels need to be reached before control is necessary, deciding whether control is actually needed and preventing the pest's occurrence by cultural methods. One means of prevention is to maintain a varied environment around your gardening space, encouraging natural predators and parasites to be on hand to act on potential pest insects.
The Enemy Within
Seldom observed in action are the small parasitic wasps that lay eggs inside or on plant-eating caterpillars. Also called parasitoid wasps if they kill the insect they lay eggs in, the wasps attack aphids, caterpillars, white flies, beetles, flies, sawflies, scale insects and true bugs. Female wasps have pointed ovipositors at the ends of their abdomens that they use to inject eggs into the bodies of the hosts. The larvae that hatch from the eggs eat the internal structures of the host insect. Most adult parasitic wasps range from the size of a printed period to about an inch long. There are many different kinds, including chalcids, ichneumonids, braconids, and trichogrammatids. Tachinid flies also oviposit eggs in or on pest insects.
The Ravenous Youngsters
A silent but raging battle occurs amid the leaves when immature stages of predatory insects move in on herbivorous pests. The purplish-black and orange larvae of ladybugs, resembling miniature alligators, stalk and devour aphids, as do their parents. Lacewing larvae with elongated gray abdomens and a long, curved pair of forward-projecting sucking mouthparts also ravage aphids. The larvae of some syrphid flower flies eat aphids, as many as 400 during the lifetime of the sluglike greenish larval fly.
Stealthy Blood Suckers
Lying in wait at the base of a leaf or inside a flower are predators in the true bug family (Hemiptera). Called assassin bugs, both wingless immature nymphs and winged adults feed on pests. Assassin bugs have long, slender antennae and sucking piercing mouthparts normally tucked under their bodies. The first pair of legs is modified to grab the prey. The assassin bug unfolds its mouthparts, stabbing them into the captured bug. It injects a toxic saliva that liquefies the prey's interior organs. The bug sucks up the resulting liquid. Spiders are also stealthy predators, most building webs to capture prey. Some spiders, such as crab spiders and jumping spiders, don't spin webs but jump on their prey to inject digestive saliva. Assassin bugs and spiders can inflict painful bites.
They Swallow Them Whole
Larger, vertebrate animals can destroy a lot of bugs. An American toad (Bufo americanus) can eat up to 1,000 insects a day, using its sticky tongue and front feet to gather them into its mouth. Adult leopard frogs eat adult and larval insects, slugs, snails, earthworms and spiders. Many lizards, such as geckos, fence lizards and whiptailed lizards, are primarily insectivorous, and horned lizards eat only ants. Birds also consume insects, some more than others. Carolina wrens eat a diet consisting of about 94 percent animals, mostly insects. Tree swallows eat flying insects for about 80 percent of their food. A nursing little brown bat female eats more than her body weight in insects a night, or around 4,500 insects.
- U.S. Environmental Protection Agency: Pesticides: Topical & Chemical Fact Sheets: Integrated Pest Management Principles
- Symbiont Biological Pest Management: Parasitic Wasps
- Bees, Wasps, and Ants: The Indispensable Role of Hymenoptera in Gardens; Eric Grissell
- Mother Earth News: Tachinid Flies
- University of Kentucky College of Agriculture, Food and Environment: Ladybugs
- Bugs; Sarah Goodman
- Oregon State University: Integrated Pest Management on Peppermint: Syrphid Fly Predators
- SoftSchools.com: Assassin Bug Facts
- University of Michigan: BioKIDS: Crab Spiders Thomisidae
- BBC Nature Wildlife: Jumping Spiders
- Photo Credit Jupiterimages/Photos.com/Getty Images
- University of Michigan: BioKIDS: American Toad Bufo Americanus
- University of Michigan: BioKIDS: Northern Leopard Frog Rana Pipiens
- University of Michigan: BioKIDS: Carolina Wren Thryothorus Ludovicianus
- University of Michigan: BioKIDS: Tree Swallow Tachycineta Bicolor
- Bat Rescue.org: Amazing Bat Facts