| Abstract |
Fly ash, one of the numerous substances that causes air, water and soil pollution, has been discovered as a pesticide against various pest forms that hamper agriculture and an active carrier in chemical pesticides (dust, wettable powder, granules and capsules) and herbal insecticides (dust) formulations. Insecticidal action of the fly ash dust was detected for the first time in the country on various kinds of insect pests inflicting crops like rice, vegetables, oilseeds, pulses, greens, fruit trees, besides pests of grains in storage yards too. Mode of action of fly ash dust on insect forms was characterised based on its physical and internal damage both on the insect bodies and crop plants. Interestingly, fly ash on application to rice soils had promoted resistance to the plant to thwart pests attack. Nano-fly ash of two fractions of size ranging down 50 mu m was detected to be highly potential in killing the pests. Four chemical insecticides, viz. BHC 10% Dust, BHC 50% WDP, Malathion 25% WDP and Carbofuran 3% WDG, were synthesized with the two selected lignite fly ash fractions. All of them faired best in killing various pest's species in rice compared to the respective chemical insecticides. It is felt that use of fly ash as a carrier in the synthesis of chemical and herbal pesticides may replace with long run the conventional carriers like Calcite, Magnesite for eventual decline in the cost, and hence, will be a breakthrough in the pesticide industry. As an attempt to exploit particle, morphology and mineralogical contents of fly ash of two sizes ranging from among 10 to 50 mu m were selected for their increased pesticidal action. SEM studies carried to have a close-up view of the individual particle of the lignite fly ash and coal fly ashes revealed that they were mostly of nanoparticle types. Secondly, morphometric features of the lignite fly ash nanoparticles were of spherical shape containing mostly of silica as silicon di oxide (SiO2) and showed two forms, namely amorphous which is rounded and smooth and crystalline which is sharp and pointed. These differently sized particles of fly ash are best suited to adhere to the body skin of the insects having dense cover of structures like fine hairs, scales, spine-like processes, nodules, pustules, ventricles. Further, such fly ash particleswhen delivered in the field through dusters cling firmly to the plants and the bodies of insects and per cent deposition was high. Mineral contents of the fly ash revealed the presence of Silica, Alumina, Calcium, Ferric Oxide and traces of Zn, Pb, Zr, Sr, S, Th, Cu, Mn, etc. Among these, silica has been observed to strengthen the pesticide property of fly ash followed by Al, Ca, Fe and sulphur. From the above, it is inferred that such nano-fly ash particle technology has great scope in pest control in agriculture and allied arenas of farm folks through promoting organic agriculture tactics. |
