Challenges and opportunities for biological control practices in India - A review

Intensive agricultural practices employing increased chemical insecticide and fertilizer applications, tillage and irrigation and heavy mechanisation (all leading to decline in the biodiversity of natural enemies) are being followed to cater to the needs of rapidly increasing human population. However, studies have clearly indicated that food can be produced in a sustainable manner by conserving biodiversity. Though majority of the studies point out that natural enemy richness enhances prey suppression, some of the studies do indicate that natural enemy diversity can even lead to weakened prey suppression due to factors like intraguild predation, behavioral interference and negative selection effects. Research conducted at ICAR-NBAIR has pointed out the benefits of conserving the diversity of natural enemies and also the effects of combinations of natural enemies on pest suppression. A classic example of biological control is that of the suppression of the sugarcane woolly aphid, Ceratovacuna lanigera Zehntner through conservation of the indigenous predators, Dipha aphidovora (Meyrick) and Micromus igorotus Banks and the parasitoid, Encarsia flavoscutellum Zehntner. This was enabled through a recommendation to refrain from applying chemical insecticides. Our studies have also indicated that combinations of biocontrol agents can enhance the overall suppression of multiple crop pests as in the case of Trichogramma chilonis Ishii with Cryptolaemus montrouzieri Mulsant for the management of brinjal shoot and fruit borer and brinjal mealybug. The compatibility of anthocorid and geocorid predators with T. chilonis has also been proved experimentally. Few studies point out the negative impacts of species richness; for eg. the biocontrol of cereal aphids by spiders was disrupted by high densities of large ground beetles. Thus, to ensure conservation and utilization of an array of effective natural enemies, we advocate advanced research on understanding and documenting biodiversity of pests and natural enemies, measuring the role played by specific or combinations of natural enemies on specific target pests and participatory research based on interactions between farmers, researchers and crop advisors.