Pest is any organism that competes with man for his food and shelter and causes discomfort, inconvenience as well as economic loss. In ancient ages, when man realized the status of pest, he utilized all possible techniques based on every day observations and general experiences. In addition to natural control, some “botanicals” were extracted from various parts of plants like roots, leaves, shoots and oils. Although these were crude in nature, but their efficacy was much satisfactory and authentic that they ruled the world before the introduction of inorganic and organic pesticides.
Biopesticides: Dare Demand of the Hour
Mazhar H. Ranjha, Shoukat Ali & Muhammad Ahmad
Pest is any organism that competes with man for his food and shelter and causes discomfort, inconvenience as well as economic loss. In ancient ages, when man realized the status of pest, he utilized all possible techniques based on every day observations and general experiences. In addition to natural control, some “botanicals” were extracted from various parts of plants like roots, leaves, shoots and oils. Although these were crude in nature, but their efficacy was much satisfactory and authentic that they ruled the world before the introduction of inorganic and organic pesticides. The discovery of organic pesticides brought a revolution in the world of crop protection and the pioneers of these chemicals were highly acknowledged for their prophetic work to make sure the food supply to the increasing human population.
Many investigations were made to know the side effects of the synthetic pesticides and in 1962 many environmental problems caused by them were brought on the arena of public. Some major limitations in pesticides changed our mood and compelled us to seek alternatives measures. Among the major constraints with pesticides are briefly discussed here. Firstly, insects have adopted resistance towards them. Secondly, they result into all categories of pollutions; air pollution by exo-drift, water pollution after their dissolve into water and soil pollution when they mix up with soil due to endo-drift which inhibits the positive activities of soil fauna including beneficial microbes which help in the improvement of texture and structure of soil. Thirdly, they have carcinogenic properties and are always an alarming danger to all human beings. Fourthly, they don’t recognize the friend and the foes and cause the brutal massacre of predators, parasites, parasitoids and many other beneficial insects. Finally, insecticides may cause an outburst of insect populations belonging to some those insect classes which resist to the contact poisons.
Generally it seems that biopesticides are merely some compounds extracted from living organisms or their decomposed bodies. Actually biopesticides are comprised of all natural enemies of pests e.g., predators, parasites, parasitoids and microbes etc., transgenic crops, botanical pesticides, growth regulators and many pheromones and these are exercised in a wise, sensible and intelligent manner to maximize the insect pest control. Each component of biopesticides is valuable and have its own worth and potential but as a whole they are one but not the same. Take a way the predators and parasites, the former is stronger then the insect pest and after classical prey they kill the host. Generally they are capable to prey at an adult age. But the later are weaker then the host, and by attacking on the pest either inside or on side the body which name them as endo-parasite and exo-parasite, depending on their morphology (mouth parts, praying organs etc.), behavior, mode of action and instinctive nature to survive, and are concerned with making the pest weaker and more vulnerable to death. Although the predators are much efficient in some cases but due to their “wandering habit” they don’t concentrate on one species (polyphagous parasites) and when there is an outbreak they fail to control it. On the other hand, parasites at their immature stage attack upon the pest and make them defenseless against different diseases and other natural hazards. They themselves irritate the pest by sucking its blood or biting it time by time and so on. The very interesting role played in nature is that there is a competition among various predators and the same case is with the parasites. So, it is very important to keep an ecological balance in the ecosystem after realizing the existing categories when there are plans to introduce imported biological agents in the same agro-ecosystem. The strict quarantine laws are obeyed to expel the not needed biological agents and after doing a number of experiments the imported predator or parasite is analyzed for its efficiency and potential and after scientific valuation it is reared and released in a good quantity. To maintain the required population of predators and parasites, the conservation of the environment and the perpetual supply of the predators are very necessary.
Insect pathology deals with the microorganisms which are harmful to insects only and which help in the control of the insect pests without damaging the other flora and fauna including human being. Among these pathogens, various strains of bacteria, viruses, fungi, nematodes etc., are visualized for the efficient insect pest control. Bt Cotton is known well to farmers in which the bacteria attacks the digestive system of the feeder or sucker and paralyses him to death. In addition to bacteria, viruses are also more effective because of their rapid growth, target killing and non hazardous effects to non-target organisms. It has been also found that the majority of viruses are effective against larval stages of insects while some others are effective against both larval as well as adult stages. The viral pesticides are more inexpensive as compared to chemical pesticides and according to some scientists they are included in “cottage industries”. A wide range of the crops and trees can be well protected against a long list of insect pests by applying microbial pesticides. The new horizons of reach are focusing on the speed of action of the viral agents and to stabilize them in light at field conditions as many of them are much sensitive to ultraviolet radiations.
The fungi are also a member of the allied forces of biopesticides against the insect pests of crops. It has been proved that when fungi are in association with bacteria, they accelerate the control of insect pests.
Botanicals, plant extracted chemicals, are to be used to replace the synthetic pesticides as their mode of action and effectiveness is synergistic in many cases. Similarly, the use of growth related hormones to unstable the regular growth of insects to make them vulnerable to all controlling agents. The promotion of botanical usage culture would also enhance the rise in forestry in countries like Pakistan where forest area is still less then five percent in spite of many efforts for a period of sixty years.
In spite of all utilities of the biopesticides, there are some limitations like resistance, less effectiveness and degradations etc. But these limitations are also there in the profile of synthetic pesticides. So there is a dire need to change the mindset of the farming community to adopt the biopesticides in place of synthetic to ensure their crop production, protection and ultimately to make sure the existing trade demands. For this purpose the governments of developing countries must promote the biopesticides by means of their media, extension work and the agro based industries which focus on environmental friendly measures like biopesticides for the control of insect pests. The most important duties is of the research workers to investigate the existing fauna related with biological control and to devise economic methodologies to exploit the biopesticides which would no doubt help the resource poor farmer to devote their best to bring forth the existing local resources to save crops with an independent task and responsibility. As a result the monopoly of the multinational pesticide companies would be on check which otherwise may sink the Titanic of agro-based developing countries like Pakistan.
