Importance of biological control in Indian agriculture
- Part 1 -

SM Haldhar, EVD Sastry, M Premjit Singh *

Pest control is an important aspect of agriculture which determines the production and productivity of crops. There are several ways by which the pests and diseases are controlled, of which the use of synthetic pesticides is common as it is cost-effective and results are immediate with the realization of dividends instant, however on the other side, these chemicals are hazardous to human health and dangerous to the environment.

Although, biological control per se has been in use in agriculture for centuries, as an industry biological control is still in its infancy. Biological control is now being advocated for an increasing number of crops and managed ecosystems as the primary method of pest control. One reason for its growing popularity is its record of safety during the past 100 years considered as the era of modern biological control (Waage and Greathead, 1988).

DebBach (1964) defined biological control as the action of parasites, predators, or pathogens in maintaining another organism’s population density at a longer average than would occur in their absence. Biological control depends on knowledge of biological interactions starting at the molecular level to the ecosystem level and is often more complicated to manage compared with physical and chemical methods.

Biological control is also likely to be less spectacular than most physical or chemical controls but is usually also more stable and long-lasting (Baker and Cook, 1974). No microorganism or beneficial insect deliberately introduced or manipulated for biological control purposes has become a pest on its own so far and there is no evidence so far of measurable or even negligible negative effects of biocontrol agents on the environment.

Singh (2004) concluded that in India, the maximum degree of success with biological control agents was achieved in the control of aquatic weeds (55%); hemipteran pests in crop situations (46.7%) followed by terrestrial weeds (23.8%).

McFadyen (2000) listed 44 weeds, which were successfully controlled somewhere in the world using introduced insects and pathogens. Biological control programs have saved millions of dollars and despite the high initial costs, are very cost-effective. The era of modern biological control, involving the deliberate transfer and introduction of natural enemies of insect pests was launched 100 years ago.

NEED FOR BIOLOGICAL CONTROL IN INDIA

The production of food grain should increase regularly to meet the needs of the growing population. Beyond good agronomic and horticultural practices, growers often rely heavily on chemical fertilizers and pesticides.

However, the environmental pollution caused by excessive use and misuse of agrochemicals, as well as fear-mongering by some opponents of pesticides, has led to considerable changes in people’s attitudes towards the use of pesticides, has led to considerable changes in people’s attitudes towards the use of pesticides in agriculture. A concomitant increase in the proportion of pests and diseases resulted in the increased use of toxic chemicals for their management.

Excessive use of synthetic pesticides has made pests resistant to these chemicals. The number of species resistant to pesticides and fungicides has increased. In recent years after the signing of the general agreement of trade and tariff of the world trade organization, more emphasis is being given to the use of eco-friendly pesticides for crop production because of their lower toxicity, higher levels of disease resistance and low residue problems.

However, biological controls should be integrated with other control measures because different methods are effective at different times and locations under varying conditions.

BIOLOGICAL CONTROL IN NORTH-EAST INDIA

In North-East India, there is huge scope of biological control because of congenial environmental condition that favours the biological control agents i.e., RH (>80%), temperature (12-350C), low pH, Rainfall (300-3000 mm) favourable for BCA, wide diversity in terms of species and strains of biocontrol resources i.e. plants, fungi, bacteria, virus, parasitoids, predators and good potential market for biopesticides for large scale cultivation of crops.

The congress grass (Parthenium hysterophorus L.) has been considered as one of the worst weeds responsible for causing health hazards in human beings and animals besides the loss to crop productivity and plant biodiversity. It was first reported in India in 1995 and now occurs throughout the country including North-East India. Parthenium was found to be grown luxuriantly in all the selected National and State Highways of North East India.

The Mexican beetle (Zygogramma Bicolorata) is a host-specific leaf-feeding beetle and proved successful for the control of P. hysterophorus. The beetle was imported by the Indian Institute of Horticultural Research (IIHR), Bangalore from the Mexican substation of Commonwealth Institute of Biological Control (CIBC).

Under the Department of Biotechnology, Govt. of India’s Twinning R & D Programme on Parthenium management in NER released 35,000 beetles in the N.E. region during 2015. From our field observations, it was observed that Mexican beetles acclimatized in the climatic condition of NE India. Field observation reveals complete invasion of road median flora by Parthenium resulting in complete changeover of the plant biodiversity in the National and State Highways of NE India.

Similarly, successful control of water hyacinth, Eichorniacrassipes has been achieved by the exotic weevil Neochetinaeichhorniae, N. bruchi @ 50,000 ha-1 and found the dispersal of the weevil in 8 districts of Assam through aerial migration and Brahmaputra river and its tributaries. In Sibsagar district of Assam > 700 ha of water body has been cleared off by the action of this exotic weevil and control achieved is about 90%.

Hazarika et at. (1994) reviewed work done on biocontrol especially in North-East India by pointing out lacunae, prospects, and the role of biocontrol in reducing the pesticidal load on tea. Somchoudhury et at. (1995) identified 38 species of predatory mites on the red spider mite in North-East India.

Studies related to spiders as predators of tea pests are scarce; however, Hazarika and Cakraborti(1998) identified 28 species of predatory spiders on mites, jassids, and aphids. They collected these species not only from tea but also from shade trees and ancillary crops. Earlier, Zhang (1993) identified and described species of spiders that prey on tea leafhoppers in China.

SUCCESSFUL STORIES OF BIOLOGICAL CONTROL IN INDIA

Biological control has been defined simply as the utilization of natural enemies to reduce the damage caused by noxious organisms to tolerable levels (DeBach and Rosen, 1991). Biological control i.e., conservation, augmentation, and introduction of exotic natural enemies has been accepted as an effective, environmentally non-degrading, technically appropriate, economically viable and socially acceptable method of pest management.

One approach to biological control has been termed “Classical biological control”, it involves the discovery, importation, and establishment of exotic natural enemies with the hope that they will suppress a particular organism’s population.

This approach has been most successful in situations in which an organism moves or has been transported to a new environment, usually without the natural enemies that have regulated its population and prevented major outbreaks. Alien species are recognized as the second-largest threat to biological diversity, the first being habitat destruction. The exotic pests in the absence of their natural antagonists, which they leave in their original home, cause unprecedented damage.

The economic impact of invasive pests is tremendous. Some successful examples of biological control have been described as following under:

BIOLOGICAL CONTROL OF PRICKLY PEAR, OPUNTIA SPP.

Prickly pear cacti, Opuntia spp. (origin: New World) were deliberately introduced into India in conjunction with the cochineal trade. These plants are also known for their edible fruits, drought resistance and emergency forage value of certain spineless forms, as botanical curiosities as well as garden ornamentals.

The first successful classical biological control was achieved in India when cochineal insect, Dactylopiusceylonicus was introduced from Brazil in 1975 in the mistaken belief that it was the true carmine dye producing insect, D. coccus. D. ceylonicus multiplied on cultivated spineless pear cactus, Opuntia ficus (= O. indica). D. ceylonicus later readily established on drooping prickly pear, Opuntia vulgaris (its natural host) in the north and central India bringing about spectacular suppression of O. vulgaris.

Currently D. ceylonicus continues to successfully control O. vulgaris, reducing it from a state of widespread abundance to that of virtual extinction in southern India and northern Sri Lanka and a relatively uncommon weed in the northern parts of India.


To be continued.....