Ask A Master Gardener – Insects: The Good, Bad and Ugly

Photo courtesy of C. Shirk

When gardeners think of insects, their first thoughts jump to the pests that plague their gardens. Those Colorado potato beetles that devour the crops, the Japanese beetles that decimate roses, beans, and seemingly anything else in their path, or the stink bugs that stink.  However, only two or three insects out of one hundred are considered pests. The remaining fall in to one of four beneficial categories.

Pollinators are one category of beneficial insects that have received considerable press in recent years with the decline of honey and native bees. Included in this category are wasps, butterflies, moths, some ants, beetles, and a few flies.  As the name indicates, pollinators distribute pollen from one plant to another and are a vital part of the food chain.  In fact, one-third of the world’s food rely on insect pollinators.

Predators are a second category of beneficial insects. These insects have voracious appetites and consume large quantities of harmful insects; about thirty percent of the insect population are considered carnivores (eat other living animals).  Dragonflies consume mosquitoes, lady beetles keep aphids in check, praying mantis eat a variety of beetles, robber flies will tackle grasshoppers, and the list goes on.  Without these predators, populations of insect pest would go unchecked.

Parasitoids is the third category of beneficial insects. These insects are particularly crafty in their method of destroying harmful insects.  They lay their eggs on an unsuspecting prey.  When the eggs hatch, the larva will feed on the host pest, killing it. Most parasitoids are in the Hymenoptera order (bees, wasps, and ants) and are so tiny they are rarely seen. They are host specific attacking only within a certain species.  Two of the most important are braconid wasps which attack tomato horn worms and ichneumonid wasps which favor weevils and loopers.

“Poopers” is the fourth and final category of beneficial insects, comprising twenty percent of the population. Scientifically, they are known as saprophagous. They feed on dead material and are the insects that clean up nature.  Within this category are termites cleaning up dead wood, fly maggots cleaning up road kill, and sow bugs cleaning up dead leaves and organic matter.  A subset of this category are the coprophages, those insects that recycle animal wastes. The most common coprophage is the dung beetle.  Without them we would live in a sorry world.

Why is all of this important? Why should gardeners care?  When pesticides are applied, they are non-specific.  They do not shake hands with the insect, get to know them first, and only kill the bad ones.  Instead, they eliminate all of them; all ninety-seven percent of the good ones along with the three percent of the bad ones.

What can homeowners and gardeners do when that two to three percent get unruly and out of hand? The first step is to identify the pest; make certain that the problem is correctly identified.  Some diseases can imitate insect damage, some insects are only a passing problem until their natural predators get wind of their presence, and some insects cause minimal damage that can be tolerated rather than treated.

If indeed there is a pest problem that needs to be addressed, first, try taking away the insect’s food, water, and/or hiding place. In other words, alter the environment to make it inhospitable for the creature.  Pulling away mulch and drying out an area where slugs are prone will discourage them.  Covering vegetables with floating row covers will deter pests from attacking vegetables that do not require pollination.  Additionally, practicing good garden hygiene by cleaning up debris, thus preventing insects from overwintering there is another way to alter the environment.

When all else fails and the existing population must be addressed, begin with the least toxic method first. Hand picking Colorado potato beetles and Japanese beetles gives a certain satisfaction when observing the bucket full of conquered pests.  Spraying a steady stream of water will dislodge an infestation of some small invaders. Soapy water sprayed on plants is non-toxic and quite effective at many reducing the population of many pests.

When all else fails and chemical applications become a must, follow all label directions carefully, use as little as possible and as seldom as possible. Be sure to wear safety gear to protect the applicator as well.  Insects are not the only creature that can be harmed with these compounds.

Garden on and stop to enjoy the insects!

Carol Shirk

Certified Master Gardener

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