Can harvesters be used to reduce botrytis in WA vineyards?
Andrew Taylor, DPIRD, Bunbury
The 2018/19 vintage in Western Australia saw cool, overcast conditions, which resulted in prolonged flowering and in some vineyards botrytis infections at harvest. These weather conditions and an interest from industry in using harvesters to remove bunch trash were the catalyst for a Wine Australia Incubator Initiative project conducted this season. The research question asked by the Incubator project is “Can post flowering harvester applications reduce bunch rot risk and manipulate bunch architecture in Western Australia?”
The basis of this work stems from experiments conducted in New Zealand where for several seasons they have found that by running harvesters over the vines post flowering, with rods above and below the fruiting zone, they have reduced botrytis incidence without affecting overall yield. Despite the success seen in NZ it was unsure whether the same results would occur in WA, given the differences in climate and varieties. As part of the incubator project, experiments were conducted in Wilyabrup, Karridale and Pemberton on Semillon, Sauvignon Blanc and Chardonnay. This was done to take into account varietal and weather differences. Further variables within the experiments were the different harvester manufacturers, speed of the harvester, beater speed, rod heights and phenology stage.
It's a common joke in research that as soon as a project is started on an issue, the issue will miraculously fail to appear. In this case, we had one of the driest seasons in the south-west of WA resulting in a very short flowering period and minimal botrytis incidence at or near harvest. This will no doubt influence the results of the project, as it will not provide a great deal of distinction between the treatments due to the overall low level of botrytis seen. Not that a low disease year is a bad thing for producers.
Despite seeing low botrytis incidence within the trials at harvest, assessments on the trash removed from bunches did clearly show that botrytis could have been an issue if the weather was conducive for its development (Figure 1). We are in the process of collating all the data from the harvested fruit to determine what impact, if any, the treatments had on bunch architecture and juice quality. Once the data is analysed a report will be finalised and available to industry.
