Abstract: The potent inducer of resistance β-aminobutyric acid (BABA) was tested to control bunch rot and virus infection in grapevine. The aim of our research was to determine the effective but non-toxic doses and the appropriate application time of BABA for influencing bunch rot in the field. We performed our studies on the grapevine cultivar Királyleányka, which has thin peeled berries with enhanced susceptibility to Botrytis cinerea. The treatments have been carried out with four different BABA concentrations (0.2, 0.4, 1.0, 2.0 g/l). The Botrytis infection rate in case of 2.0 g/l BABA-treatment was significantly lower than in the untreated control. The highest dose applied at BBCH 65 phenological state also proved to be effective on reduction of the compactness of the bunches. In another experiment developing leaves of BABA-treated vines originated from virus (GLRaV-1) infected plants became virus free. Therefore BABA could be an effective tool for regulation of grape bunch structure of cultivars with compact bunches and for moderation of grey mould (Botrytis cinerea) and virus infections.