Simulated spray drift will help understand the real thing

Spray drift from nearby broadacre crops is a potential problem common to many of Australia’s wine regions, yet we know surprisingly little about what each individual herbicide actually does to grape vines.

A new study under way at the National Wine and Grape Industry Centre (NWGIC) in Wagga Wagga plans to start correcting that situation and to test whether it is possible to identify different types of herbicide injury based on foliage and fruit symptoms.

Gerhard Rossouw’s 12-month project is funded through Wine Australia’s Incubator Initiative, which gets early career researchers directly engaged with wine regions and involved with issues of interest identified by the sector.

That’s a natural fit for Dr Rossouw, who worked as a viticulturist in his native South Africa and completed vintages in Australia, USA (California) and New Zealand before deciding to focus on the more scientific side of grapes and wine. ‘I like to link my research to the concerns of the sector because I have experience with the day-to-day side of viticulture and winemaking and can see how research can be valuable when it can be applied’, he said.

The NSW/ACT regional cluster proposed the new topic and is a partner in the project, along with another researcher from Charles Sturt University and two from the NSW Department of Primary Industries.

The project will use a potted vine experiment to assess the effect of exposure to four problematic herbicides on grapevine leaf, fruit and root metabolic responses, and the related implications for fruit quantity and composition.

A further focus will be to describe the injury symptoms (especially related to foliar and bunch development) associated with different herbicides, and link the symptoms to primary metabolic responses in the grapevine.

‘Essentially, we will be creating a simulated herbicide drift under controlled conditions, using rates that replicate what happens in the field’, Dr Rossouw said.

‘We want to be able to link what the grower can see as a symptom to what actually happens in the vine and allow them to identify which herbicide is causing the problem so that they can engage with the source of the drift.’

The work fits nicely with Dr Rossouw’s recently completed PhD, which looked at grapevine carbohydrate and nitrogen allocation during berry ripening. ‘I have quite a lot of experience in environmental stress conditions in the grapevine, and although it is a different kind of stress in this situation, there is a lot of overlap from a scientific perspective.’

Dr Rossouw came to Australia in 2013 to undertake his PhD with the NWGIC and is now an Associate Lecturer in Wine and Viticulture – as well as a researcher – at Charles Sturt University. He grew up surrounded by vines on South Africa’s west coast then completed bachelor and master degrees in viticulture at the University of Stellenbosch.

Four years in Australia has taught him to appreciate the greater use of technology in vineyards and wineries here, and the commitment to research. ‘There are many opportunities for young researchers in a lot of different fields, which is exciting’, he said.