Beneficial Insects

Mary Ann Ryan
Adams County Master Gardener

Beneficial insect is a relatively new buzz word for the home gardeners of today. This phrase – beneficial insect – refers to the good bugs, the bugs that eat other bugs that attack our garden plants – trees, shrubs and perennials. Beneficial insects are predators, parasites and pollinators that protect our plants and make them fruit.

The advantage of the beneficial insects are they improve the overall health of your plants, they lower dependence on pesticides, they save money that would be spent on costly pesticides as well as time spent on spraying plants, they will minimize exposure to humans and animals by toxic concentration of pesticides, they will promote natural populations of insects that feed on harmful pests and they help to protect our environment.

Some beneficial insects are insect specific, which means they will only eat certain bugs, like the lady bug. However, some are not specific, and will eat any insect they can reach, like the praying mantis.

Many of these insects you will find in your own garden and should become familiar.

The lady bugs have an enormous appetite for aphids – one of our most common plant pests. Some prefer scale insects and mites and are very effective on reducing infestations. The lady bug larvae are equally relentless predators. Their colorful, but ferocious appearance often causes unknowing gardeners to assume that they must be harmful. Nothing could be further from the truth.

The praying mantis is another widely recognized insect predator. Nymphs and adults alike lie in wait for an unlucky insect which strays too close, then strike out to grab it with their modified front legs.

As ugly as these may be, spiders are a man’s friend. They feed on fleas, lace-bugs, and eggs of Japanese beetles as well as sod webworms.

The Green Lacewing larvae are miniature monsters when viewed at close range. They are deadly enemies of small caterpillars, aphids, and other soft-bodied insects.

The lowly ground beetle, so common under logs and debris, is another friend of man. Both the larvae and adults are predaceous and feed on a wide variety of insects.

Hover flies, or flower flies, are common and important natural enemies of aphids and other small, slow-moving insects. The adults resemble bees or wasps, and are often seen visiting flowers, hovering over the flowers and darting around. Although hover fly larvae feed mainly on aphids, they will eat small caterpillars, thrips and other small insects. They have even been noted as predators of small European corn borer and corn earworm larvae.

Tachinid flies are parasites of other insects. After laying its eggs on the insect’s body, the fly maggots will burrow through their host’s skin and feed on its internal organs. The insect will die just as the larvae emerge and complete their life cycle.

The adults of the parasitic wasp vary considerably in size, form, and coloration, but the majority resembles slender wasps. They do not sting. They differ from the wasps that sting in that they have very long antennae. There are a great variety of hosts for these wasps such as caterpillars, moths, leafminers, wood-boring beetle larvae, flies, aphids, gypsy moth, weevils, and spiders. The larvae are internal parasites of the immature stages of the host. The parasite larva usually completes development in the host, and emerges from the host when an adult. The parasite kills the host.

The best known pollinator and man’s best friend among the insects is the honey bee.

Besides the pollinating services it renders, this insect provides us with honey which we eat and beeswax which we use in making candles, polishes, inks, and cosmetics. It is hard to imagine what life would be like without the natural pest control, flower pollination, and products provided to us by these beneficial insects.

Become familiar with these insects, as they are certainly beneficial to your garden.

Read more articles by Mary Ann Ryan