EFFECTS OF PROHEXADIONECALCIUM ON GRAPE CLUSTER STRUCTURE AND SUSCEPTIBILITY TO BUNCH ROT BOTRYTIS CINEREA IN cv GRÜNER VELTLINER
B. Schildberger, C. Faltis, M. Arnold, R. Eder
In Austria plant growth regulators have long been used on grapevines for induction of loose clusters and avoidance of Botrytis cinerea attacks. The purpose of this work was to examine the effect of a plant growth regulator containing prohexadione-calcium as active ingredient based on various parameters. The experiment was conducted on cv. Grüner Veltliner. Results were analysed on the basis of the following parameters, cluster weight and lenght, berry and seed weight, number of berries and seeds, evaluation of infestation severity by B. cinerea, and FTIR analysis. In addition, the bending index of the berries was recorded. which describes the suppleness of the clusters. The four main test variants were: (i) control, (ii) prohexadione-calcium alone, (iii) prohexadione-calcium with a botryticide and (iv) botryticide alone. Regarding the effect of prohexadione-calcium, results showed that there was a significant difference in cluster compactness. The increased number of small clusters additionally resulted in a significant increase in suppleness and reduced compactness. In 2009, B. cinerea infestation in the control was less than in the other treatments; in 2010, no significant difference was found. In 2010, the application of prohexadione-calcium led to increased must densities, compared with the control plots.