Is biological control an effective way of controlling pests?

Over 40% of the world's food production is destroyed by pests, diseases, and weeds each year. Another 20% is lost to pests after harvest. (Paoletti, Maurizio G. and Pimentel D.) Farmers usually use chemicals to control pests. However, pesticides and herbicides are an extremely harmful factor for our environment. They cause pollution in our water, air, and food. They can also kill off many beneficial insects and make infestation worse. Worst of all, it can take years for some of these chemicals to breakdown and decompose. Therefore, the use of biological control is now important. We have our environment to think about. Practicing biological pest control gives us a promising way of reducing the use of chemicals and developing alternatives that are compatible nature. So agricultural scientist tried to control unwanted plants, insects and fungi by biological methods in order to increase crop yield considerable. Biological control does not use chemical. It uses other organisms that are predators or parasites of the pest. (Indge B., Rowland M. and Baker M.) It is very important in struggle against pests that damage our agriculture and environment. Sometimes the concept of biological includes the use of genetically engineered plants to suppress pest organisms. They are all do not involved the use of chemicals.

Four types of natural enemies used by biological control against pests.

Parasitoids. This wasp is laying its egg inside an aphid where its young will develop. Parasitoid immatures develop on or inside a host, killing it as they mature. They emerge as adults and continue the cycle.

Predators. Lady beetles are well-known examples of predatory insects. A predator consumes many prey during its lifetime. The predators listed in this guide feed on insects and mites.

Pathogens. This nematode is just one example of a pathogen which may kill its host. Other pathogens include bacteria, viruses, fungi and protozoa. This section also includes antagonists which control plant diseases.

Weed Feeders. Weeds can be attacked by arthropods, vertebrates, and pathogens (fungi, viruses, bacteria, and nematodes). This weevil feeds only on one particular type of weed called purple loosestrife.

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As the method is based on using other organisms to control pests, we need to find out the beneficial organism. Biologists search the area from which the pest originally came for suitable predators and parasites to use in biological control programme. Trials are carried out to make sure that the control organism will only attack the pest, does not carry disease that it might spread to native animals or plants and can establish itself and maintain its numbers in its new environment. Then, the control organisms are bred or cultures in large numbers. They are distributed and released. Agricultural scientists collect the necessary information to find out if the programme has been successful. This set of procedure, which carries out in setting up a biological control programme, can make sure the beneficial organism is safe to use and can controlling the pests effectively.

A successful programme of biological control has a number of advantages in controlling pests:

(i) It should not intensify or create new pest problems, because the organisms used are selective. The procedure of setting up a biological control should be cagey to carry out and the products should be tested repetitiously to make sure that it is the desirable organisms.

(ii) There should be no manufacturing of new chemical. The organisms are already available and so ‘organic’. Therefore crops and soil should not be contaminated by the chemicals. Beneficial organisms are also less likely to cause damage to an ecosystem. "By using natural enemies of crop pests in a wise manner, we can replicate the balance of nature, which will allow us to produce crops sustainable over a long period of time" (Knob H.)

(iii) Predators attack many different prey species and the population densities of predators are usually quite lower compared with pest population densities. So the generalist behavior of predators is frequently very useful for regulating a variety of pests.

(iv) Parasitoid requires only one host to complete development. Usually parasitoids attack very specific pest organisms, thus they can be used in a very selective manner against particular pests. They are easily to rear, because each individual parasitoid develops within a single host. They destroy the host within which they develop.

(v) Control organisms will increase in number and spread spontaneously.

(vi) For large scale farmers these costs will be high to start but in the end you will have all you need and the costs will decrease. Biological control, in the long scheme of things, it costs less because it is self-sustaining and non-destructive.

(vii) Biological control is a long term pest control tactic. It can be a permanent solution to a pest problem and it is highly unlikely that a pest would evolve resistance to a natural enemy, as the two interacting species both would change.

There are some examples of biological control in reality

An example of this long term and permanent tactic is the Vedalia beetle. In this example of biological control, the Vedalia beetle was introduced into California for control of the cottony cushion scale in 1887. This ladybeetle saved the developing citrus industry in California and the modern era of biological control started. ()
The control of White Fly by the parasitic wasp Encarsia Formosa in greenhouses. This is now widely used as an alternative to pesticide control.
The control of water hyacinth, which was introduced to the USA from South America, by a weevil.
The use of grass carp in the UK to control weed growth in ponds and waterways. It is claimed that water temperatures in the UK are too cold for them to breed. However, the use of an exotic species such as this is still extremely controversial. ()
The most effective and environmentally safe methods of control of an invasive organism are the use of another organism – a biological control agent. This is true for Kariba weed. The salvinia weevil, Cytobagous salviniae, is a 3 mm long insect native to Brazil, Bolivia and Paraguay. It feeds almost exclusively on Kariba weed. Females lay eggs inside the leaf buds and the larvae tunnel through and feed on the horizontal stems of the plant, causing the plant to disintegrate. The adults feed on the leaves and leaf buds. Larvae take only 17-28 days to mature, so new generations of the destructive young arise frequently. The impact can be dramatic – in Lake Moondarra, Australia. 1980, the weevil destroyed more than 8000 tonnes of the fern weed in less than a year. (Miller J., Dr Sheffield L.)

To compare the advantages of biological control with that of controlling pests with chemicals, biological control have more benefits than using the chemicals.

In the United States, the Federal Insecticide, Fungicide, and Rodenticide Art, originally enacted in 1947, limits pesticides use on food. It requires users of the most dangerous pesticide – called restricted use pesticides –to have a special license to use them. The federal government may order people who use pesticide improperly to pay large fines.(Anderson M., Dede C. etc) Therefore more pest managers use biological control methods, such as encouraging a pest’s natural enemies, to instead of the use of chemicals.

To conclude, biological control can offsets the disadvantages of the use of chemicals. Therefore, biological control should be implemented whenever possible because it does not pollute the environment. It uses natural enemies of the pests for their control. Biological control should be the preferred method as chemical method causes many disadvantages when using it. Some of the reasons for using of biological control are the aspects of environmentally sound, economically feasible, time tested technique, not fully exploited, potential for use because natural enemies exist for all organisms, role in sustainable agriculture and federal mandate. (www.ento.vt.edu) Although these points are showing that using biology control is such an effective to control pests. However, there are still some people do not want practicing biology control to control pests, the reasons may be the following, need for fix, lack of patience, potent pesticides, industry advocates or easy application of pesticides. These factors lead farmers to use chemicals or other methods to control pests.