Strategic management of flowering sprays

Abstract

This project was undertaken to determine if fungicides applied during flowering are detrimental to fruit set. Laboratory and field experiments were carried out over 4 years to determine the effect of fungicides on fruit set, compare fungicide toxicity when applied during the flowering period, and whether there are differences between grape cultivars or climatic regions.

Saprophytic fungi and Botrytis were detected on anthers at flowering, with variations observed between the cultivars, area and season. Cabrio® and Filan® reduced the levels of fungi detected on anthers at flowering, and more fungi were detected on anthers from the cooler Lenswood region compared to Nuriootpa. When pollen viability was tested in vitro on agar amended with one of 9 fungicides, Rovral® and Filan® were the least inhibitory to pollen viability, and copper the most inhibitory, with no germination observed. However when fungicides were applied to inflorescences, the inhibitory effect on pollen viability was reduced compared to direct contact with amended agar.

The effect on fruit set of fungicides applied at flowering varied between treatments, grape cultivars and year of application, but there was no stand out treatment that consistently inhibited fruit set. There was no consistent correlation between high levels of stuck caps and inhibition of fruit set. Fungicides containing copper did not consistently increase the levels of stuck caps on flowers, however in some trials (but not all) there was a reduction in fruit set.

Overall these studies have shown that the application of commonly used fungicides during the flowering period is unlikely to significantly inhibit fruit set.

Summary

Effect of fungicide application during flowering on fruitset in different cultivars and regions.