RATNA KUMARI, B.HEMANTH, TARRA2022-08-102022-08-102022-08-10D6228https://krishikosh.egranth.ac.in/handle/1/5810186169EFFECT OF INSECTICIDES ON SOIL MICRO FAUNA IN RICE GROWING AREAS OF GUNTUR, PRAKASAM AND KRISHNA DISTRICTS, ANDHRA PRADESHThe present investigation entitled “Effect of Insecticides on Soil Micro Fauna in Rice Growing Areas of Guntur, Prakasam and Krishna districts, Andhra Pradesh” was carried out during kharif 2020. The findings of the survey which is intended for pest management advisory has revealed that 25.93% of the farmers’ consulted progressive farmers, followed by Agriculture Extension Officer (AEO) (18.52%) and only 14.81% of the farmers’ approached input dealers, Village Agriculture Assistant (VAA) and Scientists of Krishi Vigyan Kendra (KVK). According to 80-85% of the farmers, yellow stem borer and green leaf folder were the most predominant lepidopteran pests, while 60-65% of farmers reported the incidence of brown plant hopper and green leaf hopper. Maximum incidence of pests was noticed at tillering stage (100%), followed by boot leaf stage (92.59%) and panicle initiation stage (81.48%). Nearly 50 per cent of farmers initiated plant protection measures based on first appearance of pest and few of them (6.67%) followed the concept of economic threshold level (ETL). The frequently used insecticides for the management of the pests in rice were chlorantraniliprole, acephate, dinotefuran, flubendiamide, pymetrozine and thiamethoxam. Less than 11.11 per cent of farmers followed label claim on the container and 59.26 per cent of them were unaware of toxicity levels based on different coloured triangles on insecticide bottles. Only about 14.81 per cent of farmers used protective aids during spraying operation, while 51.85 per cent of them were aware of the effect of insecticides on soil microbes. Dehydrogenase activity (DHA) of collected soil samples from farmers’ fields estimated using spectrophotometer revealed that among three mandals of Guntur district, the highest DHA was noticed in the soil sample collected after harvesting (80.58 μ g triphenyl formazan/g soil) from Ponnur and the lowest DHA was noticed in the soil sample collected at panicle initiation stage (37.69 μ g TPF/g soil) from Karlapalem. In Prakasam district also, the highest DHA was noticed in the soil sample collected after harvesting (149.18 μ g TPF/g soil) from Karamchedu mandal. Whereas, the lowest DHA was noticed in the soil sample collected prior to xiv transplantation (60.22 μ g TPF/g soil) from Vetapalem mandal. In Krishna district, the highest DHA was noticed in the soil sample collected prior to transplantation (108.29 μ g TPF/g soil) from Challapalle mandal and the lowest DHA was noticed in the soil sample collected at panicle initiation stage (68.29 μ g TPF/g soil) from Mopidevi mandal. DHA analysis in the insecticide treated soils in vitro revealed that application of chlorantraniliprole 18.5 SC at both recommended dose (RD) and double the recommended dose (DRD) had no inhibitory effect on soil microbes in both sandy clay loam and black clay soil up to 20 DAA. On the other hand, application of cartap hydrochloride 4 G at DRD had slight inhibitory effect on DHA up to 24 HAA with a value of 49.27 μ g TPF/g of sandy clay loam and 160.90 μ g TPF/g of black clay soil compared to control. However, application of imidacloprid 17.8 SL at both RD and DRD resulted in significant drop in the DHA of both the soils even up to 20 DAA. Dinotefuran 20 SG at both RD (51.16 μ g TPF/g soil) and DRD (43.05 μ g TPF/g soil) had inhibitory effect only up to 24 HAA in sandy clay loam soil. Inspite, in black clay soil, inhibitory effect was noticed only up to 24 HAA at recommended rates (147.54 μ g TPF/g) and even up to 10 DAA at DRD (125.54 μ g TPF/g soil). Pymetrozine 50 WG at RD had significant inhibitory effect on the DHA in both the soils (50.77 μ g TPF/g of sandy clay loam and 150.55 μ g TPF/g of black clay soil) compared to their controls up to 24 HAA. At DRD, significant inhibitory effect was noticed even up to 10 DAA and 20 DAA. Among all the treatments, chlorantraniliprole at RD was found to be the safest molecule and imidacloprid at DRD was found to inhibit DHA to a greater extent with mean value of 115.69, 136.37 and 163.60 μ g TPF/g of chlorantraniliprole treated soil and 61.37, 48.79 and 48.18 μ g TPF/g of imidacloprid treated soil at 24 HAA, 10 and 20 DAA, respectively. Enumeration of bacteria and fungi in the insecticide treated soils in vitro revealed that chlorantraniliprole 18.5 SC at both RD and DRD had no significant inhibitory effect on bacterial population in both the soils with mean value of 245.37 x 10-6 CFUs/g at RD and 242 x 10-6 CFUs/g at DRD. But the fungal population declined slightly in both the soils (28.33 x 10-4 CFUs/g in sandy clay loam and 36.33 x 10-4 CFUs/g in black clay soil) at DRD of chlorantraniliprole compared to control. Application of cartap hydrochloride 4 G at DRD had inhibitory effect on bacterial and fungal population in both the soils compared to control. Imidacloprid 17.8 SL at both recommended and DRD resulted in significant decline in bacterial and fungal populations in both the soils with a mean value of 146.50 x 10-6 bacterial CFUs/g soil and 19.83 x 10-4 fungal CFUs/g soil at DRD. On the other hand, application of dinotefuran 20 SG and pymetrozine 50 WG at both RD and DRD resulted in remarkable declination of both bacterial and fungal populations in both the soils compared to control.EnglishThesis