Management Strategies for Zero Fungicides Residue in Grapes

Abstract

Research was attempted for growing grapes by using pesticides whenever obligatory and keeping time of applications and choice of pesticides such that at harvest residue will be minimum possible. Strategically outlook for control of diseases was different before fruit set and thereafter. For the management of downy mildew, dithiocarbamate group, such as mancozeb are used, due to which use of bio-control agents as spray was not possible. Induce systemic resistance (ISR) activities of microbes was exploit, to achieve highest ISR activities use of Trichoderma was given before and instantly after fruit pruning. For years, grapes powdery mildew management is dominated by use of trialzole fungicides. But in recent year resistance to triazole fungicides in powdery mildew accentuated up to 50 ppm. Therefore, strategically it was decided that triazole fungicides will not be used 60 days after fruit pruning. The sulfur was safer substitute, an obvious choice which meant if only sulfur was sprayed bio-control agents also can use. Only sulfur and bio-control agents such as Trichoderma and Ampelomyces were used in all FLD locations 60 days after pruning with alternation, till about 15 days before harvest. Based on bio-efficacy experiments chlorine dioxide, nano silver in complex with hydrogen peroxide were selected as ecologically low profile chemicals for management of powdery mildew. In all four FLD plots on this strategy was implemented and in all FLD plots disease PDI for downy mildew, powdery mildew and anthracnose were kept to be bare minimum. Dissipation of pesticide residue in vineyards may be dependent on many factors; microbial degradation is one of such important factors. ICAR-NRCG has developed and commercially formulated Bacillus subtilis name DR-39 applied at 2.5 g/L as effective dose to increase the rate dissipation of about 10 pesticides. Total fungicide residues detected in grapes from different FLD, during 2017-18 was in the range of 0-3. All fungicides detected were below MRLs (Maximum Residue Limits) and their concentrations were very less in parts per billion (ppb) range. The shelf life of the grapes grown in zero residue plots, per cent physiological weight loss (PLW) and per cent rotten berries were found less as compared to farmers practiced plot. The FLDs have success for growing grapes without any detectable pesticides residue (zero residue grapes) by using updated technology and strategy.