Ecology And Environment

What is Biological Control



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When we think of  our options for using biological controls, there is the sledgehammer, the negotiation, and the treaty with our natural enemies. In the past, the sledgehammer included fire, extremely toxic pesticides, and mass killing of pests and predators that decimated our food crops, caused food to spoil; spread disease processes or which infested and destroyed property.

 Now, biological control is oriented more toward introducing natural enemies that are benign for our purposes, but effective in decimating pests.  With a combination of research, production and publication, the biological control movements are working to introduce and to encourage new methods and biotechnologies to the public.

 What is being controlled? Generally included are “…viral, microbial, nematode, insect, mite, weed, and vertebrate pests in agriculture, aquatic, forest, natural resource, stored product, and urban environments. Also included are arthropod pests of human and domestic animals.” 1

 The approaches that are encouraged are ecological, molecular and biotechnological and the goal is to understand these new forms of control. The approaches include Conservation, Classical Biological Control, Augmentation, and Purchase and Release of Natural Enemies.

 In purchase and release of natural enemies, the natural enemies of insect pests are called biological control agents and include predators, parasites and pathogens.  With natural enemies of weeds, biological control agents that are specific plant diseases are used. These are called “antagonists”.

 In most natural situations, antagonists and natural enemies keep populations in balance, but such predators as ladybugs and praying mantises can be purchased and placed in gardens to control pests with their voracious appetites. Other biological control predators and natural enemies have complex gestations and growth cycles, including some which are parasites of parasites!

 In conservation, there is an understanding that predators and pests have natural behaviors, gestations, reproduction and life cycles. They are specifically adapted to certain environments and prey on specific populations. Observing and knowing their conditions allows for enhancing the environment with benign and helpful predators.

 Other methods involve minimizing the comfort levels for harmful pests and predators with the use of pesticides or insecticides, but only as needed and in the most selective manner possible.  In some cases, not using pesticides or insecticides at all for a while allows the natural facts about pests to be observed and understood so that a specific, target approach can be taken.

 Classical biological control is long term and inexpensive, as it involves introducing specific predators and natural enemies to attack very specific pests, such as the Vedalia beetle which helped to control the cottony cushion scale that was destroying California’s citrus crops.

 Augmentation is a biological control where a supplemental release of natural enemies is conducted. This can be at specific times of the growing year as “inoculate release”, or in massive quantities as “inundate release”.

 Finally, the habitat may be manipulated or modified to give some help to the natural enemies of the pests.  Weedy borders, hedgerows and other refuges, for example, provide flowers and nectar that help the beneficial predators to establish themselves.

 Other biological controls include applying substances such as dormant oil and copper spray to trees to prevent dormant burrowing pests from completing their emergent stage and to prevent fungus growth during very wet seasons.  Gardeners know about “tangle foot” or other ways to prevent ants from climbing plant stems and establishing aphid colonies. Simple methods of using flat containers that are filled with water and a few drops of cooking oil to drown and prevent earwigs which are seeking water from climbing into trees or plants. Planting new garden plants with a “collar” prevents slugs and insects from getting to the seedlings. Gopher screen can be placed under the soil to prevent gophers and moles from eating tender roots. Finally, soap based insecticides can prevent bad insects from decimating gardens, while not harming the beneficial insects, such as ladybugs and praying mantises.

 As a result, biological control by the modern methods or by the classical methods are being used by the back yard gardener as well as the giant farming operation to make sure that pests and our natural enemies are kept in check without introducing massive amounts of toxic material into the environment.


1.  http://www.elsevier.com/wps/find/journaldescription.cws_home/622791/description



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