Pk. Smith et Tv. Price, VICTORIAN VEGETABLE GROWERS ESTIMATES OF THE INCIDENCE OF DOWNY MILDEW ON BRASSICA CROPS, CROP LOSSES AND FUNGICIDAL CONTROL, Australasian plant pathology, 25(2), 1996, pp. 99-105
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.