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DALY: Contrary to popular beliefs, most insects are harmless

Timothy Daly

Timothy Daly

Next to the microbes, insects are the most diverse organisms on earth. Estimates put the number of individual species at more than 100,000 in North America alone. In your backyard, there are hundreds or even thousands of insect species present at any given time. However, the sight of them can be disturbing to many. True, some species damage our lawns and garden plants, inflict painful stings, carry diseases and cause damage to structures. However, these represent less than three percent of all insect species. The other 97 percent are harmless or even beneficial. They play an important role in the ecosystem. Life on earth as we know it could not exist without them.

Insects pollinate a large number of plants species, particularly many of the fruit trees and vegetables we use for food. Honeybees are perhaps the most familiar. Their decline due to a variety of factors has affected fruit production in many areas of the country. Honeybee hives are sometimes shipped to orchards in order to provide pollination where natural populations are lacking. Other pollinators include bumble bees, butterflies, moths, and certain species of flies and beetles.

As scavengers and decomposers, insects play a vital role breaking down dead organic plant and animal material whereby the nutrients are returned to the soil. Flies and dung beetles decompose manure from large animals and increase the rate of decomposition by fungi and bacteria. Termites are destructive insects in that they damage wood in building structures. However, in the wild, they consume dead trees and other plants where they break the material down for nutrient recycling. Roaches, ants and other insects which can infest our homes also play a role as decomposers in natural areas.

Several species of insects feed on pestiferous ones. Lady beetles and lace wings are predators of soft bodied insects such as aphids, whiteflies and mealybugs. Recently the Mall of America in Bloomington, Minn., released over 70,000 lady beetles to control an outbreak of aphids on its thousands of indoor plants as an alternative to using pesticides. Several species of wasps and flies also parasitize harmful insects. An example is in vegetable gardens where tomato hornworms sometimes can be observed with small white balls attached to them. These are the cocoons of a species of parasitic wasps that lays eggs on the host and the larvae feed inside it. Even hornets, wasps and yellow jackets prey on some pestiferous caterpillars. Spiders, which are not insects but in a class of organisms called arachnids, control insect pests. Praying mantids, which are insect predators, are territorial. There may be only one mantid in a given area, which limits the amount of prey it can catch and consume.

Frequently, nurseries and other sources of horticultural materials offer living beneficial insects for sale. Their drawback is that once they are released into the environment, they will disperse and will seldom remain just in your garden. To have conditions conducive to supporting these insects, reduce the use of insecticides and only apply if absolutely needed. Also, certain plants are attractive to some species. Examples include Queen Anne’s lace, yarrow, dill, fennel, and parsley. They provide food and shelter to many species of parasitic wasps, flies and others. Consider planting some of them in your garden.

Insects are very diverse, and most species are not detrimental. They provide us with food, control harmful insects and help break down dead organic matter. So next time you encounter insects, even the bad ones, realize they are in the minority and that many others are beneficial.

Timothy Daly is an Agricultural and Natural Resource Extension Agent with Gwinnett County. He can be contacted at 678-377-4010 or tdaly@uga.edu.