Assessing disease management in Western Australian vineyards
Abstract
Assessing disease management in Western Australian vineyards
Summary
Western Australian grape growers had previously reported problems with powdery mildew, Botrytis and downy mildew despite using comprehensive spray programs.
The study was therefore based around three questions:
- Are the current disease management methods effective?
- If not why not?
- Is further research/work needed?
Twelve, 11 and 12 growers volunteered from Margaret River, Pemberton and Great Southern respectively to participate in the study.
A block of Chardonnay was chosen on each property and the growers used a standard recording booklet. They recorded disease incidence and severity at critical phenological stages, factors that may have predisposed vines to disease during the season, and methods used to manage disease- cultural, biological and chemical (detailed spray diaries).
Only a third of the growers completed the study booklet, however this provided useful information for the final workshops which were held in June in the Great Southern and at Pemberton.
Very little disease was apparent in the study blocks early in the season. However there was a good deal of summer rain that gave a significant risk of all three diseases in all regions. There were also tight bunches and, in some cases, berries damaged by hail or birds. Early symptoms of powdery mildew were fairly common as was Botrytis bunch rot. Downy mildew symptoms were also seen in two instances. However, most growers were able to control all of these diseases with negligible harvest loss. The use of cultural methods was quite variable, however most growers were satisfied that their canopies were not too dense. The use of biological control was also variable. Chemical methods used showed some similarities but also varied widely in the numbers and timing of sprays. Most people felt they used the right chemicals at the right rates.
Overall, the growers at the two workshops felt that current methods of disease control were mostly effective. However the effectiveness was sometimes reduced due to weather problems, gaps in spraying schedules and spray coverage issues.
The growers concluded that further work should include a costing study of disease control practices (a benchmarking study) and a series of half day training workshops practical sessions on disease control and spray technology.