VICTORIAN VEGETABLE GROWERS ESTIMATES OF THE INCIDENCE OF DOWNY MILDEW ON BRASSICA CROPS, CROP LOSSES AND FUNGICIDAL CONTROL

Victorian vegetable growers were surveyed by mail-out questionnaires t o quantify the importance of brassica downy mildew in 1992. Of the 59 respondents, 41 (70%) grew brassicas principally in Bairnsdale, Berwic k, Cranbourne and Werribee shires. The main crops were cauliflowers, c abbage and broccoli. In 1992, downy mildew was reported by 78% of seed ling producers and by 30% of growers. Downy mildew was considered more detrimental (moderate to serious) in the field (84%) than by seedling producers (50%), although all nurserymen ranked it as a serious probl em and considered that more studies of it are required. Downy mildew o ccurred throughout the year and was most prevalent between July and Oc tober. Disease incidence was greatest in the shadehouse, although ther e was also a high incidence in the field. Fungicidal control was used by 66% of growers and most (74%) alternated their fungicides. Dithane was the most commonly used fungicide (85%), but mancozeb, either prote ctants, acylalanines and phosphonates were also used. The survey sugge sted growers required more guidelines on fungicide spraying frequency and application techniques. Problems with inadequate fungicide control were reported as early as 1970 and occurred mostly in the shadehouse with copper-based protectants, dithiocarbamates and acylalanines.