Friday, August 29, 2014

Pests of Pests – Farmers’ Friends

Any crop ecosystem contains a balance of community of organisms living in harmony with the environmental factors. Community of organism is the food web prevailing in the place in order to facilitate decomposition and nutritional cycle. The balance is maintained according to the non-biological factors like temperature and moisture. The process of adaptation and survival of the fittest are in full swing. In agriculture, the natural balance is disturbed and importance is given to the prolific growth of any one or more crop which is of economic importance or human interest. In such situations, a new ecosystem is developed for any particular cultivation – Paddy ecosystem, pulse ecosystem, wheat ecosystem.
Paddy ecosystem consists of Paddy crop, the soil, the microbes dwelling in the soil which decomposes the crop residues and determines the fertility level of the field, group of insects – live on paddy for their survival (Pests) and organisms feed on pests. Pest is any organism causes economic damages and hindrances for the existence of crop or human being. Pests in agriculture causes damage to the crop growth and either kills the plant or create economic loss by drastically reducing the yield.
By encouraging the growth organisms which feed on pests we can effectively keep the pests in control in a natural way. They are called Natural Enemies. They are the real heroes in keeping the agricultural scenario pesticides-free. They facilitate death, weakening, or reduced reproductive potential of harmful pests. The commonly visible natural enemies are insects and spiders, they feed on plant feeding insects and protect crop from economic loss. Natural enemies can be classified into two broad types – Predators and Parasitoids.
Predators consume one or more living prey insects. Predatory behavior is common in insects, spiders and mites. Common predators are spiders, mites, ladybird beetles, dragon fly, and bugs. The diversity of predators in agro-ecosystem is enough to keep pests in control. When predators could not keep pest population below economically damaging levels, they actually slow down the rate of pest population increase. But the pesticide usages have disturbed the balance of such Biological shields of crop. Predatory insects, spiders and mites feed on any or all stages of their prey, by killing, disabling eggs, larvae, nymphs, pupae or adults.
  • Beetles chew their prey.
  • Bugs inject toxins into their prey and immobilize, later suck their juices.
  • Dragon flies catch their prey in flight
  • Praying Mantis wait for their prey, camouflaged and catch their prey by surprise.
  • Spiders trap many pests with their web and consume later.
  • Hover flies hover and dart in flight.

Parasitoids live in or on the body of their host insect during at least part of their life cycle. Parasitoid is the term used to describe an insect that parasitizes and kills its insect host. Endoparasites insert their eggs into a host’s body. Ectoparasites lay their eggs and their larvae develop on the outside of the host’s body.
A typical female parasitoid searches

for a host insect and, depending on the species, deposits one or more egg in or on the host. The eggs hatch and develop inside the host insect. When parasitoid development is complete, the parasitic larvae emerge and pupate outside the host, or, in the case of many parasitoids, pupate inside the host insect and emerge as adults. Most parasitoids are in the wasp (Hymenoptera) and fly (Diptera) orders. There are a few species of beetles (Coleoptera) that parasitize other insects. The small group of twisted-wing parasites (order Strepsiptera), consists entirely of parasitoids. Parasitoids are categorized based on their host stage they attack as egg, larval, and cocoon parasitoids. Many parasitoids are small and difficult to see.

Field release of egg parasitoid Trichogramma japonicum at weekly intervals during egg laying stage of rice borer in very effective as the parasitoid kills the pest in the egg stage itself before the pest could cause any damage to the crop. Trichogramma chilonis at weekly intervals keep leaf folders on control as the parasitoids lay its egg in stem borer larvae hence kill the pest, multiplies themselves and spread rapidly. It is very economical as the Tricho-cards are low cost inputs. Cost involved to control the pest otherwise is detrimental both economically and environmentally. Let us choose a GREENER way of pest control to live longer healthily.