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Lignite fly ash as eco-friendly insecticide

By Our Agriculture Correspondent

Fly ash when dusted on vegetables and rice offers adequate protection against chewing and sucking pests.

THE LIGNITE and coal fly ash, which is considered as a nuisance in the thermal power plants and its environs, is a potential and eco-friendly insecticide. "We have found that it can be used to keep both the chewing and sucking pests of rice and vegetables at bay," says Dr. P. Narayanasamy, Professor of Entomology, Faculty of Agriculture, Annamalai University, Tamil Nadu. Researching on the insecticidal properties of fly ash, Prof. Narayanasamy has found that more than 50 species of insect pests of various major crops were susceptible to fly ash treatment.

He has standardised the dosages and time of application for rice. He has established that fly ash can be effectively used to manage the serious rice pests such as leaf folder, yellow caterpillar, spiny beetle, ear head bug, brown bug, black bug and grasshoppers. Even sucking pests such as brown plant hopper (BPH) and green leafhopper (GLH) are also eliminated when fly ash liquid diet is fed, according to Narayanasamy.

Scientists from other research centres have also proved that the fly ash could be effectively used to ward off pests of vegetables such as brinjal, bhendi, tomato and cauliflower.

Serious polyphagus pests such as Helicoverpa armigera and Spodoptera litura, which are major enemies of cotton, have also been found to be controlled by the application of fly ash. It has been found that the fruit yields of brinjal, bhendi and tomato increased significantly when dusted with fly ash. "Based on our experiments with the lignite fly ash (LFA) and coal lignite fly ash (CLFA), we have worked out schedules for dust application to control the major pests of rice and vegetables.

For rice, the dust formulation has to be applied on 30th, 40th, 50th and 60th days after transplanting. A dose of 40 kg per hectare is recommended for effective control of the pests. The same dose is recommended for the vegetables such as brinjal, bhendi and tomato, but the time of application varies with the crop," he explained.

For instance, it has to be applied on 20th, 35th, 50th and 65th days after sowing in the case of bhendi. For brinjal, the fly ash should be dusted on 35th 50th, 65th and 80th days after transplanting.

In the case of tomato, the dust formulation should applied on the 30th, 45th, 50th and 75th days after transplanting.

Fly ash can be used as an additive in the preparation of fungal bio-pesticides to control BPH and GLH. It has been found to induce resistance in rice against BPH and GLH. It protects stored paddy from the red flour beetle infestation, and guards the field population of friendly insects, which are natural enemies of rice pests.

Fly ash has also been found to interfere with the mouthparts and digestive system of the larvae of crop pests and help in eliminating them. In addition to being an insecticide, fly ash can be used as a soil amendment in light porous soils, and as a micronutrient provider for deficient soils. Fly ash can be used as conditioner to arrest soil erosion, and to induce plant resistance against diseases such as the blast fungus of rice, according to Narayanasamy.

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