Excess use of chemical causes development of resistance: - It happens because of repeated application of chemicals.
Pest resurgence: - In pest resurgence same pest comes in more severe form in the subsequent season. It happens because of killing of natural enemies also reproductive potential is enhanced.
Outbreak of secondary pest: - As in case of cotton outbreak of secondary pest i.e., white fly is seen while primary pest, which is present, is bollworm. Same is case of mites which is also a secondary pest.
Undesirable side effect on non-target organism: - Honeybee is one of the non-target organisms, which gets affected due to the excess use of chemicals. Others like some predators, which are important in maintaining balance of nature, and thus ecological balance also gets disturbed.
Pesticide residue presence in harvested crop and creation of environmental pollution: -Pesticide residue is major problem in chlorinated and organophosphorus compounds they are not easily degraded. In Chlorinated hydrocarbon bio-magnification occurs i.e., pesticide residue goes to the soil then passes to H2O and through water it enters in the body of organisms or in food chain these molecules get accumulated in fats and therefore their concentration increases. Biomagnification has long term effect such as teratogenic (birth defect), carcinogenic effect particularly seen in birds whereby thickness of shell gets reduced. Sometimes lethal mutation also occurs.
Doses used are very high :-In case of chemicals doses used are very high i.e., almost 1-2 kg a.i/ha but now they have been reduced for e.g. case of synthetic pyrethroid 400 gm/ha, in case of imidachloprid 50-100 gm/ha are used.
Direct hazard in application of pesticide: -As farm workers are not trained and they get exposed to pesticide due to which they may get affected. In methomyl (carbamate) it is very much hazardous and has may create problem while application because of ethanol content. Mostly in case of carbamate insecticide it happens except carbaryl. Methomyl facilitates its penetration into egg cuticle and thus have ovicidal action but at the same time penetration into human body is also more and therefore soluble liquid formulation of Methomyl is banned and likely to be introduced in the form of granules or W.P. also Phosphomidon is banned because of residual problem and even after washing they cannot be removed and therefore are banned.
Ever-increasing cost of pesticide: - Pesticides are based on petroleum product and once the cost of petroleum increases then cost of pesticide also increases. Also due to increase in awareness among public about environmental safety the registration procedure for pesticides have became severe and it takes 5-6 years for registration.
Newer molecules, which are introduced, are complex and are difficult to synthesize.
Ag.
Technologies
(Pest Mgmt.)
