Testing new postharvest disease management options for table grapes

Managing Botrytis rot in table grapes is critical to maintaining fruit quality, especially for export markets. Sulphur dioxide (SO₂) release sheets have long been the industry’s frontline defence, but until recently, the options available to Australian growers have been relatively limited.

Applied Horticultural Research (AHR) has just completed a trial comparing two new SO₂ release sheets, developed by a South African company aiming to enter the competitive Australian market, against the widely used sheets and an untreated control.

The trial used popular table grape varieties, Jack’s Salute and Sugar Crisp, harvested from vineyards in Mildura. AHR’s Dr Jenny Ekman selected 40 boxes of grapes, which were stored under controlled conditions at the Fresh Produce Group’s cool store for eight weeks.

Throughout storage, the grapes were assessed for critical quality indicators:

• Botrytis rot presence

• Sulfur bleaching (a common side effect of SO₂ exposure)

• Berry shatter

The results were highly encouraging. The new sheets performed just as well as the industry-standard sheets, effectively controlling rot without increasing sulphur bleaching. Visual assessments, including comparison images of a control box of Sugar Crisp versus the biodegradable sheet, demonstrated the product’s efficacy.

This new product could offer Australian growers a valuable alternative, potentially with benefits in terms of cost efficiency and sustainability, as the new sheets are biodegradable.

The data from this trial will now be prepared for submission to the Australian Pesticides and Veterinary Medicines Authority (APVMA) to support registration, which would open the door for commercial use in Australia.

From top left: Dr Jenny Ekman under the vines in Mildura, control box with no sheets, box with sheets, AHR’s Deme and Ruben assessing grapes