What are the factors that develop in the bunch rot? The two main causes are the residues that remain trapped in the flower clusters and rosure caused by moths of the screw. What interventions can be vital to defend the botrytis bunch? Also called botrytis gray mold rot is the most serious of the vine and can be combated with actions ranging from chemical control to agronomic management of the vineyard. Excellent results were obtained using chemical thinning with gibberellic acid that killing the flower reduces the compactness of the cluster making it less susceptible to pathogenic infections. The improvement of the microclimate can also be obtained through stripping the area of the bunch.