Late biological fungicide spray keeping grape bunches clean

David Lewin is Operations Manager at Westralian Nominees Pty Ltd’s vineyard property in the Jindong/Kaloorup region that predominantly sells to Calneggia Family Vineyards and several other Margaret River wineries.

Surrounded by mainly dairy and beef enterprises and comprising sandy loams through to deep red loams that also are ideal for potato growing, the vineyard was established in the late ‘90s and was under the Evans & Tate banner in the early 2000s. It won International Red Wine of the Year with its Shiraz at the turn of the century, when the vines were only a couple of years old.

Shiraz is still the main variety grown, together with Cabernet Sauvignon, Merlot and some Sangiovese and Malbec red varieties, while the chief white varieties include Chardonnay, Sauvignon Blanc and Semillon. 

David has been associated with the property since 1999, punctuated by a stint with vineyard management business South West Labour Solutions at Margaret River from 2008-2015.

He said the Jindong/Kaloorup area generally received average annual rainfall of around 600 millimetres, and while it was about 150 mm down for the current season, rains in late summer before harvest can cause problems with botrytis, particularly in the late-season Cabernet Sauvignon.

“We can also get dewy mornings that can be equivalent to a couple of millimetres of rain,’’ David said.

“2017 was the most recent bad year with botrytis, when we dropped one in four bunches on the ground, and we also received a lot of rain in March this year. With no blossom in the surrounding bush, we also had a big issue with bird peck, which allows botrytis to infect the damaged fruit.

“We put nets on after the last spray, but it’s a very expensive exercise to put them on and off if you have a rainfall event and need to spray. Our blocks are commercially-grown, so we sacrifice the outside row or two and net the remainder.

“It’s really expensive if you have to put people on the ground to drop fruit. It can cost you $2000 per day and the fruit you are losing can be another $1000-2000/ha on top of that – and that’s only allowing a couple of tonne/ha of fruit.’’

He said during the spray season, they normally liked to use Teldor® at 80% cap fall (or E-L 25 growth stage) over everything, followed by Switch® fungicide at pre-bunch closure (E-L 29 or 4 mm berry size).

“If it’s a dry season, we might use chlorothalonil instead of Teldor, or between the applications, or on the less susceptible varieties and Teldor or Switch on the more susceptible varieties.’’

David said they traditionally monitored the long range forecast and there would be a last spray on the white varieties at least 30 days before picking, whereas with the Cabernet crop it could be 60 days plus.

“Generally the last sprays were at the end of January and then we might not pick the reds until April.’’

He said after 4 mm berry size, biological fungicides were now the main option and earlier this year they trialled Serenade® Opti.

Containing the unique properties of the pure QST713 strain of Bacillus amyloliquefaciens (also known as Bacillus subtilis) bacteria, Serenade Opti is a formulated combination of spores and fungicidally active compounds. It acts as a fungicide by preventing spore germination and germ tube elongation and penetration, and as a bactericide by direct contact activity. The product also has the ability to activate the plant’s natural disease resistance mechanisms.

In addition to its use in grapevines, Serenade Opti also controls botrytis in strawberries, suppresses bacterial spot in tomatoes, capsicums and chillies, and has recently been registered for stem end rot and anthracnose in avocado, mango and other tropical fruit crops.

“It has no withholding period, so we can spray it very late,’’ David said.

“In March when we knew the rain was coming, we applied Serenade Opti and Botector™ about five days before the weather event and then followed it up seven days later. Some blocks received two applications of Serenade Opti and some received Serenade Opti and then Botector. We also used Eco-protector.’’

Bayer Territory Business Manager Ian Cook said it was best to apply Serenade Opti prior to weather events.

“We used the Serenade Opti in two different blocks of Cabernet that traditionally can get botrytis. It was applied five to seven days before the rain and then seven days after and we never had a botrytis event,’’ David said.

He said they planned to continue the trials with Serenade Opti this season.

“We will do a couple of Cabernet blocks and a block of Sangiovese that is prone to botrytis. We will apply the Serenade Opti at pre-bunch closure, so it closes up clean with the bunch.’’

“We also might apply it on a Semillon block that has had minimal pruning. It’s a commercial block and a very heavy cropper.’’

“We are generally picking the whites a lot earlier with the current winemaking styles, so there is less botrytis, but Semillon is very prone to it, as well as Sauvignon Blanc and Chardonnay to a lesser degree.

“Serenade Opti gives you a new option late in the season and the fact we have used it and got good results is great. We may progress to using it at 80% cap fall as well.

“It is an alternative approach and it is another mode of action. And anytime you can use less chemicals, it’s a good thing. We are now trying to reduce our herbicide usage within the vineyard.’’

The biological fungicide has been applied using a Croplands 4000-litre Quantum Mist sprayer at 250 g/100 L of water and with 500-1000 L of water, depending upon the canopy size, to target the bunch zone.

Serenade Opti is compatible with many commonly used insecticides, fungicides and other treatments. When used as directed, it is also soft on most beneficial insect species, including predatory ladybird beetles, green lacewings, parasitic wasps and predatory mites.

David said they had good numbers of lacewings and ladybugs at the property, with a protea farm nearby supporting the beneficial insect population.

ENDS