Pollination of Vitis inifera L. cv. Pinot noir as influenced by Botrytis fungicides

The effects of fungicides on grape (Vitis vinifera L. cv. Pinot Noir) pollen germination and tube growth were studied in vitro, and a related field trial examined effects of time of fungicide application during flowering on seed number and fruitset. Fungicides pyrimethanil, cyprodinil + fludioxonil and chlorothalonil incorporated into in vitro germination medium at the recommended mixing rate for field application all prevented pollen germination. When the fungicides were diluted to 10 % of the recommended mixing rate, pollen grain germination was still completely inhibited. Further dilution to 1 %, resulted in some pollen grains germinating but the level was significantly less than the control, and the grains that did germinate had stunted pollen tubes (< 100 mm in length), compared with controls not exposed to fungicide (800 mm in length). In a 0.1 % dilution of the fungicides, germination percent was not significantly different to untreated control, however pollen tube length was still slightly suppressed in media containing pyrimethanil (523 mm) and cyprodinil + fludioxonil (366 mm). In spite of these marked effects on pollen germination and tube growth in vitro, plants sprayed with pyrimethanil at either 5 or 80 % cap fall, resulted in no significant reduction in fruitset. Seed set however was affected, with seed number per berry being significantly reduced on inflorescences that were sprayed at 5 % cap fall.