In this essay we will discuss about the cultural, behavioural and biological methods adopted for Integrated Pest Management (IPM).
Cultural Methods for Integrated Pest Management (IPM):
Agronomic adjustments, necessary for higher yield, are at the same time are directed at preventing mass multiplication and spread of pests by modifying the crop microclimate.
It includes removal or destruction of breeding refuges and over wintering of pests. Seed material, farm yard manure etc. carrying insect eggs or its stages of development should be carefully screened before their use. Destruction of alternate hosts minimises pest population buildup.
b. Tillage and Inter-Cultivation:
Ploughing and inter-cultivation brings about unfavourable conditions for multiplication of pests as well as diseases and weeds. Quiescent stages (pupae) of harmful organisms will be exposed to dehydration or to predation by birds and other stages may be mechanically damaged or buried deep in the soil.
c. Cultivar Selection:
Cultivars with high yield potential and quality without resistance to pests and diseases are the main causes of frequent epidemics and mass multiplication of pests and diseases. A large number of cultivars resistant/tolerant to pests and diseases have been developed to suit different agro-ecosystems. Selection of such cultivars can bring down the losses considerably.
d. Time of Sowing:
As weather influences developmental rhythm of plants as well as growth and survival of pests and diseases, serious set-back occurs when the weather conditions are such as to bring about coincidence of susceptible growth stages with highest incidence of pests and diseases. Therefore, adjustments in sowing dates are often resorted to as an agronomic strategy to minimise the crop losses.
Maize sown late suffers little borer damage, as by then the egg parasite Trichogramma is able to keep down the population of the pest. Rice may suffer less from borer attack if planted early (early June). Early maturing cotton cultivars have become popular in Punjab and Haryana as they escape pink bollworm.
e. Plant Population:
Plant population per unit area influence crop microclimate. Dense plant canopy leads to high humidity build up congenial for pest and disease multiplication. Keeping the total plant population constant, inter and intra row spacing can be adjusted to minimise the humidity build up within the plant canopy.
f. Manures and Fertilisers:
Excessive nitrogen increases susceptibility of crop to sucking and leaf eating pests. Higher rates of nitrogen application than the recommended rate to hybrids without corresponding increase in phosphorus and potassium is the main factor for heavy pest and disease incidence. Balanced applications of NPK help the crop to tolerate pests and diseases considerably.
g. Water Management:
Irrigation can reduce the soil inhabiting pests by suffocation or exposing them to soil surface to be preyed upon by birds. Irrigating potato crop at tuber formation can minimise potato scab. Anthracnose of beans, early blight and charcoal rot of potato can be checked by furrow irrigation than sprinkler irrigation.
h. Habitat Diversification:
Many pests prefer feeding on a particular plant to others. This preference may be exploited to reduce the pest load on crop. Crop rotation, intercropping, trap cropping and strip-cropping can bring down the pest load considerably.
Behavioural Methods for Integrated Pest Management (IPM):
Pheromones are ectohormons secreted by an organism, which elicit behavioral responses from other members/sex of its own species. These are extremely selective, non-toxic, highly biodegradable and effective at low application rates.
Synthetic sex pheromones are commercially available and are used for surveillance, monitoring and control of many lepidopterous pests such as spotted bollworm, tobacco caterpillar, potato tuber moth, diamond back moth, leaf folder etc.
These are volatile compounds that evoke behavioural response adaptively favourable to the receiver. Fairomones are released either by the host plant or by the host insects. While the former issued by the pest and natural enemies to locate their habitats, the later is used for prey finding and parasitisation/preying.
Fairomones from host plant can be effectively used to mass trap pest species as well as for monitoring. Use of fairomonal compounds to increase the efficiency of the predator C. carnea and the egg parasitoid T. chilonis has been successfully demonstrated.
Biological Methods for Integrated Pest Management (IPM):
Biological control of insect pests is gaining recognition as an essential component of successful IPM. Classical biological control involves deliberate introduction and natural establishment of natural enemies in areas where they did not previously occur.
In addition to deliberate introduction of bio-control agents, proper attention needs to be given for conservation and augmentation of natural enemies that already exist in an area. This should be treated as important as many insect predators are much more susceptible to insecticides than the pests they attack. Biological control agents for insect pests are available in nature abundantly.
Pathogens causing diseases in insects and destroying them:
Nuclear polyhedroses viruses (NPV)
Grunulosis viruses (GV)
Insect Parasitoids (Parasites Thriving on Insects):
Insect parasitoids include:
Commonly used predators are:
These predators feed on mealy bugs, coccids, scales and mites on citrus, grapevine and guava. Mirid predator Cyrtorhinus attack brown plant hopper of rice. Insect predator Chrysopa is effective on aphids, mealy bugs and young caterpillars.
Natural occurrence of diseases caused by microorganisms is common in both insects and weed populations and is a major natural mortality factor in most situations. Use of microorganisms for pest control involves their culture in artificial media and later introduction of larger amounts of inoculum into the field at appropriate time.
Many fungi and bacteria can be handled in this way but insect viruses have the limitation that they have to be raised in living insects. As the bio-control agents (microbial pathogens) are applied on the targeted pests in much the same way as chemical pesticides, they are often termed as bio-pesticides or natural pesticides.
Bacillus thuriungensis, a bacterial pathogen infesting a wide range of insect pests, is the most common microbial insecticide in use today. It is used against caterpillars that attack a wide range of crops. Unlike most other chemical insecticides, it can be used on edible products upto the time of harvest. It is selective in action and does not harm parasites, predators or pests.
Another bacterium B. Popilaleis also commonly available against white grub Papillae japonica and Hototriclia sp. amongst insect pathogenic fungi, commercial preparations of Verticillium lecauii are available for the control of aphids, thrips and whitefly under glass house conditions.
Some weeds like lantana, notchi, tulsi, adathoda etc. act as natural repellant to many pests. Trees like pungam, wood apple, anona and their byproducts have excellent insecticidal value in controlling diamond back moth, heliothis, white flies, leafhoppers and aphid infestation.
Most commonly used botanicals are neem (Azadirachta indica), pungamia (Pungamia glabra) and mahua (Madhuca indica). Neem seed kernel extract (2 to 5 per cent) has been found effective against several pests including rice cutworm, diamond back moth, rice BPH, rice GLH. tobacco caterpillar, aphids and mites.
The pesticidal ingredients of neem formulations belonging to general class of natural products called triterpenes, more specifically, limonoids. They act as repellents and also disrupts growth and reproduction in insects. Commonly known limonoids are Azadirachtin, Meliantriol, Salannin, Nimbin and Nimbidin.
The efficiency of vegetable oils in preventing infestation of stored product pests such as bruchids, rice and maize weevils has been well documented. Root extracts of asparagus work as a nematicide for plant parasitic nematodes. Similarly, leaf extracts of many plants can inhibit a number of fungal pathogens.
Use of Insecticides:
The current pest control technology relies heavily on pesticides. In India, its consumption in 1956 was only around 200 t as against 200,000 t during 2000. Outbreak of Heliothis armigera on cotton crop in Andhra Pradesh due to liberal use of synthetic pyrethroids is indicative of things to come in future.
Pesticide residues in agricultural commodities are the issues of major concern besides their harmful effects on desirable flora and fauna. Equally worrying issue is about resistance in pests to pesticides. Under these dangerous circumstances, the viable option to plant protection is IPM in which pesticides use is one of the components in the system.
Pesticides should be used only when cultural and biological methods of controls are not in a position to manage the pest problem. Under unavoidable circumstances, recommended pesticides alone should be used in rotation at recommended rates.