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The concepts of “beneficial” and “pest” are strictly human defined. All organisms serve a useful purpose in the ecosystem, and are therefore, by default, beneficial. As the term is applied here, however, it means any living thing that benefits the environment around us (humans), including insects, spiders, mites, nematodes, birds, reptiles, mammals, plants, bacteria, fungi, and viruses. The benefits they provide include pest management, pollination, and maintenance of soil health.
The opposite of beneficial organisms are pests. Any organism can be considered a pest, by humans, if it negatively affects those humans (see Is It Really a Pest? for more). These living things can be detrimental to human needs and may damage plants, sting, bite or spread diseases.
Below are pictures of some beneficial bugs that you might see in Maine. Adults are usually pictured, because that is what is most often seen by homeowners; keep in mind, however, that other stages of the insects may be providing the benefit.
For example, honey bees are usually thought of as beneficial because they pollinate crops and produce honey; however, if a swarm takes up residence in your home and you get stung, you are more likely to define them as pests. Even plant-feeding organisms may be considered beneficial if they are feeding on unwanted plants like purple loosestrife but if those same bugs start devouring your favorite petunias you may not think of them as beneficial.
Organisms are said to be beneficial when they help reduce pest damage. The action of one living organism controlling the populations of another organism is called biological control and the organisms that feed on pests are called natural enemies. Virtually all insect and mite pests and a few plant pests have some natural enemies. Learning to recognize and encourage these natural enemies can help reduce pest populations and consequently reduce pest damage and the need for costly pesticides or other control measures.
Natural enemies are classified into three general groups: predators, parasites or parasitoids, and pathogenic organisms. Predators are selected for their ability to feed directly on nuisance insect or plant species. An example of a predator is the green lacewing which feeds upon aphids or Galerucella beetles that eat purple loosestrife.
Parasites, or parasitoids, have complicated life cycles which involve laying their eggs within a living insect host or invading their bodies directly. An example of a parasitoid is the winsome fly which lays its eggs on the backs of Japanese beetles. Hb nematodes are parasites which find their way inside grubs and other insects through their many breathing holes (spiracles) or through their digestive system. Pathogens are essentially bacterial, fungal, or viral organisms which disrupt the lifecycle of nuisance insects or plants. A widely used bacterium is Bacillus thuringiensis (Bt), which has the potential to control caterpillars like gypsy moth, Colorado potato beetle larvae and mosquito larvae (wigglers). Beauveria bassiana is a fungus that can be used to control ticks.
You can help these important organisms by growing the right types of plants which provide food and cover.
Want to Know More? Links to More Information about Beneficial Organisms
[Photos, left to right: (assassin bugs) Louis Tedders, USDA Agricultural Research Service, Bugwood.org; (big-eyed bugs) Russ Ottens, University of Georgia, Bugwood.org; (brown lacewings) Joseph Berger, Bugwood.org; (damsel bugs) Alton N. Sparks, Jr., University of Georgia, Bugwood.org; (dragonflies and damselflies) David Cappaert, Michigan State University, Bugwood.org; (green lacewings) Frank Peairs, Colorado State University, Bugwood.org; (ground beetles) Joseph Berger, Bugwood.org; (lady beetles) Russ Ottens, University of Georgia, Bugwood.org; (long-legged flies) Joseph Berger, Bugwood.org; (mantids) Tom Coleman, University of Kentucky, Bugwood.org; (minute pirate bugs) Bradley Higbee, Paramount Farming, Bugwood.org; (predaceous stink bugs) Russ Ottens, University of Georgia, Bugwood.org; (predatory wasps) David Cappaert, Michigan State University, Bugwood.org; (robber flies) David Cappaert, Michigan State University, Bugwood.org; (soldier beetles) Jim Occi, BugPics, Bugwood.org; (spiders) ; (syrphid flies) Steven Katovich, USDA Forest Service, Bugwood.org; (tiger beetle) David Cappaert, Michigan State University, Bugwood.org; (parasitic wasps) David Cappaert, Michigan State University, Bugwood.org ; (tachinid flies) John A. Weidhass, Virginia Polytechnic Institute and State University, Bugwood.org; (bees) Johnny N. Dell, Bugwood.org; (butterflies and moths) Ronald F. Billings, Texas Forest Service, Bugwood.org; (yellowjacket wasps) Gary Alpert, Harvard University, Bugwood.org]
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