New biological fungicide a boon against botrytis in SA vineyard

Image: Scott Degenhardt, Agronomist with EE Muir & Sons at Penola, and Brian Nitschinsk pictured inspecting the vineyard at Mount Benson Estate, near Robe in SA’s Lower South East.

Brian and his wife, Carolyn, operate the 40 ha Mount Benson Estate property, located alongside the coastline at Mount Benson, near Robe in the State’s Lower South East.They purchased the property in 2015 and moved there the following year after having grown grapes near Romsey in Victoria’s Macedon Ranges.

Mainly Shiraz and Cabernet, plus some Merlot and Sauvignon Blanc grapes, are grown over about 24 ha, with the fruit sold to Taylors Wines (Clare), Cape Jaffa Wines and Gapsted Wines in the Victorian Alps.

The property comprises good, red sandy loam to a depth of about 1 m over limestone and also features a limestone block house, Cellar Door, Gallery, venue for events and a seasonal cafe.

Brian said heavy dews were common from early February onwards, providing ideal conditions for botrytis development, and, with their fruit being some of the last harvested in the region, protective sraying and moniotoring was essential.

“It’s equivalent to getting a couple of millimetres of rain overnight. The vines are wringing wet at 7 am and still damp at 10 am in the morning,” Brian said.

“We also get a sea fog, like an inversion layer, even in February. The heavy, damp fog comes across and unless you have protection in place, you can be in a world of hurt.

“Harvest for us is in the cooler weather around Easter / Anzac Day / first week of May. So keeping the fruit clean in these last four to six weeks is critical.”

To do this, he said they had been applying the foliar fungicides Barrack Betterstick^® at 80% cap fall, followed by Switch^® at bunch closure (less than 4 mm, peppercorn size) and it had been quite effective, however the latter had recently raised some residue concerns, albeit at very low levels. Hydrogen peroxide sprays were used last season, however they tend to soften the grape skins and have no residual activity.

As a result, and the fact they are trending to more organic style production, for the last vintage they decided to apply the new biological foliar fungicide, Serenade^® Opti, from bunch closure.

Serenade Opti, from Bayer, contains the unique properties of the pure QST713 strain of Bacillus amyloliquefaciens (also known as Bacillus subtilis) bacteria and is a formulated combination of spores and fungicidally active compounds produced by the spores. It acts as a fungicide by preventing spore germination and germ tube elongation and penetration, and as a bactericide by direct contact activity and through activation of plant resistance.

In addition to its use in grapevines, Serenade Opti also controls botrytis in strawberries and suppresses bacterial spot in tomatoes, capsicums and chillies.

“Setting ourselves up at pre-bunch closure with an effective spray and then using an alternative effective product without residue concerns in the last couple of weeks – those are the sprays that are really critical to keeping our fruit clean,” Brian said.

“We wanted something on the soft side and the preventative side that we could use right up to harvest, and the Serenade Opti is fresh new chemistry and reasonably priced, so it’s excellent – it was just brilliant.”

“Every couple of years we can still use Switch in the rotation. We can mix it up – and that’s really important (for resistance management).”

He said using Serenade Opti at bunch closure helped to keep the inside of the bunches clean.

Image: “Brian Nitschinsk, Mount Benson Estate, says using the new biological foliar fungicide, Serenade Opti, to prevent botrytis helped to keep the inside of bunches clean prior to the recent harvest. He says the fact there is no withholding period with Serenade Opti makes it really attractive.”

“You need the inside of the bunches clean prior to bunch closure. Several weeks post-harvest, the fruit low on canes not picked by the harvester was still in reasonable condition despite 80 mm of rain, being under the canopy in the shade and with quite a bit of moist grass in the vine row below. It kept it clean.”

Brian said as a biological fungicide, the no withholding period also made it really attractive.

“We did a second spray close to harvest after we received 10 mm of rain and then some damp, dewy mornings and warm days with no winds. It costs a bit over $2000 a time to spray the vineyard with Opti, but it’s cheap insurance against having fruit rejected.”

“Our last Opti spray ended up about 10 days before (harvest) due to the rain and then harvest date coming forward. But having that protection in place gives us an extra couple of weeks if we need it.”

Serenade Opti is compatible with many commonly used insecticides, fungicides and other treatments, which Brian said was a bonus and also saved a pass, as he applied Switch by itself.

“With one of our earlier sprays of Serenade Opti, we used copper and sulphur,” he said.

The Nitschinsks applied the biological fungicide at 250 g/100 L of water and used a water rate of 700-800 L/ha through their Silvan Turbomiser sprayer.

When used as directed, Serenade Opti is soft on most beneficial insect species, including predatory ladybird beetles, green lacewings, parasitic wasps and predatory mites. 

Scott Degenhardt, Agronomist with EE Muir & Sons at Penola and who previously worked as vineyard manager at Zema Estate and earlier with Rymill in the Coonawarra, said with the now limited availability of botryticides in the industry, Serenade Opti was promising as a key product that was well priced and “ticked all the boxes”.

“In what was a challenging year, it showed a lot of potential for use in the future, particularly right up to harvest, when there was a higher risk period,” Scott said.

He said various growers through the region applied Serenade Opti at 80% cap fall or around the pea size bunch closure stage.

“Particularly with the way it was on the coast, I certainly advised people to take on board that it was the product they had to use in the last month.”

“With the very dewy nights, it was a great fit to put some protectant on to provide some peace of mind that you could get through to harvest, with everything being held-off to the 15-16 baume stage.

“In some cases, you needed something to get you through. If we had a reasonable rainfall event, it (botrytis) could have got to a damaging stage. There was enough around – you could find it if you looked for it. But Serenade Opti certainly was the best option for late season cover,” he said.