An ominous set of findings point towards a food frenzy by insects – triggered by global warming. A new leaf fossils study presented in the 11th issue of a journal titled, ‘Proceedings of the National Academy of Sciences’, shows eating boom during warming 50 million years ago. The same thing could happen during our current period of warming. Researchers think more voracious insect appetites are result of a concurrent rise in carbon dioxide levels that would have made plant leaves less nutritious. If this trend was in reality to take shape it is perhaps time to rethink about chemical usage in agricultural systems and propagate a healthier predator-prey system whereby we are prepared with a knowledge matrix between the planner and the farmer.
Almost every food that we consume offer traces of pesticides on examination. Pests and weeds, no doubt, are unwanted subjects in a farming cycle, yet their method of extermination needs an urgent change as nearly all agrochemicals – that include fertilisers, severely damage our environment. We are today constantly devising ways to increase awareness and improve technology yet translating the improvement to the grassroot levels is an arduous task. Pesticide and fertiliser use have taken a strong hold of our nation post green revolution, with farmers refusing to tryout newer non-intrusive methods of cultivation. Rising indebtness strengthens fear of crop failure and in turn increases dependence on chemical usage.
Altering the genetic structure
Scientists have world over devised changes within the structure of plants so that it can ward off pests on its own – without further human assistance and chemical usage. Popularly known as genetically modified (GM) crops, such plants are enabled to make their own insecticide, most commonly a poison produced by the bacterium Bacillus thuringiensis (Bt). Although still shrouded in controversy in India, Bt cotton, is a case in point that has greatly reduced the use of insecticides against cotton bollworm. In future developments, plants are also being made resistant to viral diseases. Besides genes that enable plants to fix their own nitrogen may be fixed within cereal plants, reducing the need for artificial fertiliser. Crops are also likely to be modified to improve their nutritional quality. However, there are some drawbacks to this seemingly easy solution. Although reports claim that GM crops have caused no harm to consumers or to environment during their first ten years of widespread use, there are still questions that need answers. We still do not know for certain whether genes from a GM crop can spread into wild plants and, if so, how far would these genes travel. Then, if these genes do enter wild plants, are they likely to produce ‘superweeds’, more resistant to natural predators and herbicides. And how difficult would such weeds be to control as the existing superweeds that have escaped, for example the yellow star thistle and purple loosestrife in the United States, or Japanese knotweed and wild rhododendron in Britain, and Parthenon and Prosopis juliflora or vilayati babul in India.
The Predator Prey Policy
In a well managed organic farming system, pests and weeds are considered to be part of the system itself as they do not usually get out of control. As in nature, even in agricultural ecosystems, predators appear to do a good job if they are not disturbed with chemical usage, especially pesticides. In California in the 1940s, $750,000 was spent to introduce a European beetle to control a particular weed that was killing cattle. It has reportedly saved ranchers over $100 million. Another example is the white fly, a common insect pest found on greenhouse plants. It can be controlled by introducing a small parasitic wasp called Encarsia. Chemical interventions however, in effect, end up killing the predator and developing resistant target species resulting in a huge influx in pest population.
Trap species and other methods
Many farmers use prophylactics such as diluted cow urine and vermiwash (the fluid from a vermicompost tank) both of which can also be used in greater strengths as pesticides. Where prophylactics do not work, a number of non-chemical methods of pest control may be used. Some of these include, use of pheromone and light traps (for moths and other insects), use of predator species, growing trap crops (which involves planting more than one crop, where the naturally occurring insecticides in trap plants thwart the spread of pests in the other), use of microbial pesticides and biological agents like Heliothis, Spodoptera, Trichogramma, Trichoderma, etc., and use of natural pesticides. Such bio pesticides may be easily prepared from neem, ginger, chilli, vitex negundo (Indian pivet tree), custard apple (the seeds), pongamia pinnata (pongam/karanj), asafoetida, turmeric, garlic, tobacco, sweet flag, nux vomica, tulsi, Persian lilac, Adathoda, Ipomoea, and more. Pesticides from plants rarely persist in the environment and can be manufactured economically.
Using biological controls has been receiving considerable public interest in recent times. The control agents include parasites, predators, diseases, protozoa and nematodes that attack the insect pests besides exploring possibilities of genetically modifying plants and creating effective bio pesticides. Biological methods of pest control are often more economical although in a post green revolution era, dependence on chemicals have risen to such a degree that replacement may take a considerable period. The Indian Government is yet to workout policies that would direct masses towards organic farming and are at present deriving lessons from pilot ventures mainly in organic composting methods. In an era where the fallout of global warming is beginning to make its presence felt, changes in the pest pattern will surely affect cropping systems. Urgent plans should be afoot to train farmers in cultivating holistic cycles of providing plant nutrition and at the same time keep pests at bay. However, biological pest control needs caution, especially when a predator is imported from another ecological regime. Non endemic species have the capacity to take over systems on an invasion mode which can have unexpected negative results.