Alex McKay, wine maker at Collector Wines, has this year begun using a naturally occurring kaolin clay that reflects ultraviolet and infrared light while allowing usable light in.

"Sunburn has been an issue, not every year, but especially in summer these years with extremes during January and February," he said.

It depends on the orientation of the rows: "If you have north-south vine rows you have the western sun coming almost perpendicularly onto the vine and it can be very strong and detrimental.

"Those vineyards and blocks would have the most trouble with sunburn."

Sunburn begins to occur in January although the grapes aren't harvested until mid-March. "In one particular vineyard, we would drop up to about 20 per cent of the group, which is quite a large economic sacrifice.

"This year, after we applied the sunscreen, we only had a sunburn incident of five per cent and we believe this year had more extreme conditions during January than a normal year. We've had a good result."

The sunblock was used on Tempranillo, Sangiovese, Shiraz and a smaller volume of Riesling. "Until now our best defence was irrigation, so keeping an eye on the weather forecast and keeping an eye on any water in the ground before any major heat events," he said.

Charles Sturt University (CSU) postdoctoral researcher Dr Joanna Gambetta said sunburn could "affect up to 15 per cent of wine grape berries in Australia in any given season."

Sun protection on vineyards has been used since the early 2000s, and now CSU is investigating the impact of the timing of leaf removal on sun damage to grapes. The research is examining vineyards in NSW and will develop a set of guidelines for growers to further reduce the impact of sunburn damage to their grapes.

The project is by Dr Gambetta of the National Wine and Grape Industry Centre and funded by Wine Australia.