Biological control is the use of a biological agent, not necessarily a vertebrate species, against the pest organism to create control. The most common biological control procedure is the introduction of a predator into the pest population. The predator must be studied carefully before its introduction to ensure that it will not become a pest, because predators are not obligate and often prey on species other than the target species, especially when placed in new cituation. To introduce pathogenic organism is another way to control populations biologically. When introduction of such organisms into pest populations is contemplated, a thorough study should be conducted to identify the potential hazards of the introduction, since the organisms are usually exotic rather than endemic. Following factors must be considered before disease organisms are introduced.
The biological-control organism must be highly pathogenic to the target species.
The killing power of the organism must be anticipated.
The organism must be host-specific.
The organism must be available under environment must be suitable for its perpetuation and spread.
The control programme should be monitored to establish the actual adverse and beneficial effects of the introduction.
Advantages of Biological control
Biological control agents are self-propagating and self-perpetuating: ideally, once introduced, biological control agents will persist in time, and may spread over large areas from the points of release and reach targets that chemical can’t reach.
Biological control is a cheap method: This method is usually free of charge as far as farmer is concerned and may be the only economic solution for some forestry and pasture problems and for many tropical crops grown which have low inputs and unable to carry the cost of an insecticide.
The technique is selective with no side effect: Biological control agents are prey-specific, and obviously do not carry any kind of environmental dangers associated with insecticides.
The development of resistance of pests to biological control is unlikely.
Disadvantages of biological control
Biological control acts slowly: Biological control agents take some time to spread from there point of release, to build up in numbers and to make there impact on pest population. During this period when the pest may still be present at intolerable levels, any use of pesticide against it or other pests on the crop can endanger the biological control system.
Biological control limits the subsequent use of pesticide: When biological control agents are being used against one pest, it is very difficult to continue using insecticides against other pests on the same crop. This may make the use of biological control impossible unless biological control system can simultaneously be set up against other pest insects.
Biological control is not an exterminant: Biological control system if intended to be self-perpetuating, involves the present of the prey even if only at low levels. Growers therefore cannot expect to have a totally clean crop as they can with insecticides.
Biological control may be unpredictable.
Techniques of biological control
Inoculation
Inundation
Conservation
Inoculation
Inoculation is applicable where the problem is wide spread and the crop needs little insecticide against other pests. Here it is necessary to ship a large variety of potential natural enemies back to the home countries, where they are kept in strict quarantine conditions to eliminate diseases and other sources of mortality. During the quarantine phase, a number of studies will be carried out on the selected agents to assess their potential suitability in the field. In general it is desirable that the species should have a high searching capacity, so that they will not emirate readily when host number declines. It is also important that the species is adapted to the wide range of climatic variation.
Inundation
This is the use of biological control as a biological pesticide. Large number of natural enemy are reared in the laboratory and released on to the corp. The aim is to create and outrageously high ratio of biological control agent to pest so that pest is exterminated, the biological control agent itself dies out, and pesticides can then safely be used.
Conservation
Here maximizing the activity of Indigenous natural enemies by either avoiding the large-scale distraction when insecticides were used or by improving the environmental conditions to enhance their survival and activity.
Ag.
Technologies
(Pest
Mgmt.)
