Mitigation of flubendiamide residue in rice by probiotic lactic acid bacteria

Abstract

Similar to crop pests, residues on crops following application of pesticides need to be managed to mitigate their impact on the environment in a sustainable strategy. Residues of flubendiamide, one of the latest generation pesticides commonly applied on rice foliage to manage yellow stem borer, Scirpophaga incertulas (Walker) and leaffolder, Cnaphalocrocis medinalis (Guenee), need to be managed to reduce its impact on natural enemies, human beings and cattle. Generally regarded as safe and commonly used in fermentation as probiotics, the lactic acid bacteria (LAB) are likely to address the problem of flubendiamide residues in rice. newlineIn this attempt, a semisolid LAB formulation rich in Lactococcus lactis, Lactobacillus pentosus, Enterococcus faecalis and Lactococcus garvieae made from milk powder, cane jaggery, fermented grape juice and egg mixed to flubendiamide 20 WG was evaluated in the laboratory, screenhouse and field experiments at two doses, i.e. 25 g a.i. ha-1 and 50 g a.i. ha-1 during 2017-2019 at Tamil Nadu Agricultural University, Coimbatore. The dissipation of flubendiamide residue on rice leaves was assessed both by a new qualitative instant residue indicator drop (iRID) method wherein a water drop was placed on the leaves before recording its surface tension effects in terms of contact area (mm2), contact angle (º) and capillary rise (mm) and by ultra high performance newlineliquid chromatography (UHPLC). Their persistence in acidic, neutral and sodic soils was determined only by UHPLC. The results indicated that the residues of flubendiamide 20 WG at 25 g a.i. ha-1 and at 50 g a.i. ha-1 dissipated in 8 9 days on rice leaves in the field as detected by the instant residue indicator drops, whereas UHPLC-determined halflife averaged 4.3 days. newlineIn the laboratory experiments with different types of soil, addition of LAB at 1 ml / 200 g of soil accelerated the dissipation to BDL of flubendiamide 20 WG at 11 mg / 200 g of soil by 15 days, with half-lives averaging 24.0 days without LAB and 21.4 days with LAB in