Dissipation Kinetics and Environmental Risk Assessment of Thiamethoxam in the Sandy Clay Loam Soil of Tropical Sugarcane
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Dissipation Kinetics and Environmental Risk Assessment of Thiamethoxam in the Sandy Clay Loam Soil of Tropical Sugarcane Crop Ecosystem T. Ramasubramanian1 · M. Paramasivam2 Received: 9 April 2020 / Accepted: 24 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Thiamethoxam 75 SG has recently got registered for use against shoot borer and termites of sugarcane. It is the only neonicotinoid having label claim against both the major pests of sugarcane. The dissipation kinetics and environmental risk assessment of thiamethoxam 75 SG were studied in a typical tropical sugarcane crop ecosystem as detailed reports are lacking. Rapid and sensitive method adopted to determine the residues of thiamethoxam in the soil employing HPLC could provide more than 95.5% recoveries. The insecticide was observed to persist in the sandy clay loam soil for 60 days and reached below the detectable level of less than 0.01 mg/kg (LOQ = 0.01 mg/kg) on 75th day when applied @ 120 g a.i./ha. The half-life was worked out to be 16.50 days. At double the recommended dose (240 g a.i./ha), the insecticide persisted up to 75 days with the half-life of 16.91 days. The risk quotient values indicated medium to low level of risk to earthworms during the course of degradation of thiamethoxam in the soil. Keywords Thiamethoxam · Persistence · Dissipation · Sugarcane · Risk assessment Worldwide sugarcane is cultivated in more than 110 countries. India ranks second in terms of area under sugarcane and its production, next only to Brazil. In 2018, India’s share was 19.76% of world’s sugarcane production from 18.01% of world’s acreage under this cash crop (FAO 2020). Though the Indian sub-continent occupies the prestigious position in cane cultivation, the yield per ha remains static (70.3 ± 3.5 tonnes/ha) for more than a decade since 2007 (FAO 2020). Among the several biotic and abiotic stresses responsible for the lower productivity of the crop, insect pests are the major ones accounting for about 20% of the loss of cane yield in the country (Dhaliwal et al. 2015). Although 125 insects were recorded as pests of sugarcane (Box 1953), only 18 of them are still considered as major pests (Gupta 1957). Shoot borer and termites are among the 18 major pests, causing * T. Ramasubramanian [email protected]; [email protected] 1
Division of Crop Protection, ICAR-Sugarcane Breeding Institute (Indian Council of Agricultural Research), Tamil Nadu, Coimbatore 641 007, India
Pesticide Toxicology Laboratory, Department of Agricultural Entomology, Tamil Nadu Agricultural University, Coimbatore 641 003, India
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extensive damage to sugarcane crop year after year across the Indian sub-continent. The sugarcane varieties, which are under cultivation, are equally susceptible to both the pest species. Also, the biocontrol agents are yet to be exploited to the level of expectation in managing both the species of pest insects. Therefore, the shoot borer and termites are generally brought under check with chemical mea
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