STUDIES ON INSECTICIDE RESIDUES IN PADDY GROWN IN SOUTHERN AGRO-CLIMATIC ZONE OF ANDHRA PRADESH
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Date
2019
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Acharya N G Ranga Agricultural University, Guntur
Abstract
The present investigations on “Studies on insecticide residues in paddy grown in Southern Agro-climatic zone of Andhra Pradesh” were carried out in Department of Entomology, Pesticide Residue Laboratory, Institute of Frontier Technology (IFT), Regional Agricultural Research Station (RARS), Tirupati and college farm, S. V. Agricultural College, Tirupati during rabi seasons of 2016-17 and 2017-18.
The results of the field survey which was conducted at paddy growing farmers fields of Southern Agro-climatic zone (Chittoor, S P S Nellore and Y S R Kadapa districts) of Andhra Pradesh on pesticide usage pattern during rabi, 2016-17 and 2017-18 revealed that, most of the rice growing farmers were males with an age group ranging between 40-50 years leading nuclear family and without any education (illiterates). A higher seed rate of 25-30 kg acre-1 and the adoption of seed treatment with fungicides were followed by majority of farmers. During the crop growing stages, most of the farmers applied higher dosages of fertilisers and to control the weeds preferred manual weed control. Among the insect pests and diseases, the yellow stem borer and blast caused damage in all the farmers (100.00%) fields. During tillering, panicle initiation, milky and grain formation stages of the paddy crop, all the farmers (100.00%) applied insecticides and fungicides. Most of the farmers used insecticides belonging to organophosphates, followed by fungicides and herbicides during the crop growing season. Before application of pesticides most of them preferred to contact pesticide dealers for pesticide recommendations and used approximate quantity of pesticides while preparing spray solutions. Most of the farmers used power sprayer for spraying
during the morning or evening hours by wearing shirts with full sleeves. After the application of pesticides at weekly interval, the majority of the farmers threw the empty bottles in trash.
The detection of insecticide residues in milky and harvested grains of Southern Agro-climatic zone of Andhra Pradesh during rabi, 2016-17 and 2017-18 revealed that, in milky grains, more insecticide residues of organophosphates followed by anthranilic diamides and neonicotinoids were observed. In the harvested grains and straw samples, very less number of samples were detected with residues belonging to antharanilic diamides.
Chlorantraniliprole 18.5 SC proved as the most effective insecticide with the lowest Dead Hearts (DHs) (9.50%) and White Ear Heads (WEHs) (4.22%) where as cartap hydrochloride 50 SP proved as least effective with 14.80 percentage of DHs and 13.84 percentage WEHs against paddy Yellow Stem Borer (YSB), Scirpophaga incertulas (Walker) damage. The efficacy of ten insecticides against Cnaphalocrosis medinalis (Guenee) during rabi, 2016-17 and 2017-18 revealed that, all the tested insecticides had significantly affected the larvae of C. medinalis and reduced the leaf damage over untreated control. Chlorantraniliprole 18.5 SC proved as the most effective insecticide with the 4.95 percentage of paddy leaf damage and the least effective was cartap hydrochloride 4 G (7.39%) against paddy leaf folder damage. The influence of test insecticides against S. incertulas and C. medinalis on paddy grain yield showed that, all the treatments showed significantly higher yields over control (42.56 q ha-1). The highest yield was recorded in the chlorantraniliprole 18.5 SC (58.19 q ha-1) treated plots and the lowest was recorded in cartap hydrochloride 50 SP (47.33 q ha-1) treated plots.
The dissipation pattern of the certain insecticides in paddy leaf, grain and straw samples at different interval of time after second insecticidal application in both the seasons viz., rabi, 2016-17 and 2017-18, revealed that, all the insecticides showed some residues for particular interval of time in leaf samples, while the residues of BDL (Below Detectable Level) were observed in grains 30 days after application and in straw samples of paddy 60 days after application. The carbofuran and cartap hydrochloride 4G insecticide residues increased in paddy leaves from zero to one day after second insecticidal application and later dissipated following pseudo-first order kinetics and reached to BDL after 21 days. The insecticidal residues viz., acephate, cartap hydrochloride, chlorantraniliprole, chlorpyrifos, dichlorvos, flubendiamide, monocrotophos and profenofos followed the first order kinetics in their dissipation behaviour and individually reached to BDL at 14, 7, 14, 14, 10, 10, 45 and 30 days after second insecticidal application.
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D5851
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