Monday, 17 September 2018 12:49

From vintage to viruses

Written by  Tessa Nicholson

Now into its 10th year, the New Zealand Winegrower Grape Days have become a benchmark in information transfer.

And members are obviously appreciative of it, given the record numbers that turned out in June to the three sessions.

From the details of Vintage 18, that showed a slight increase in yields over last year, through to how viruses could become a grape grower’s best friend, the day was packed with information and research findings. 

In this article we take a look at some of the knowledge that was passed on to those attending.

If you would like more detail, visit the nzwine.com members website. All the presentations are on line. 

Reducing herbicide use in vineyards 

Presented by Mark Krasnow

It has long been a practice of growers to spray under vine weeds to prevent competition. It has entailed multiple sprays, leaving the ground bare for the summer months. But is this necessary? Does the growth under the vine really impact on the yields and chemical makeup of the fruit? Mark Krasnow has been exploring those very questions.

With Glyphosate being classed as a category 2A carcinogenic  by the World Health Organisation, there is an urgent need to come up with alternatives to its use. 

“There is a movement in Europe to actually ban Roundup and if that happens they are going to start putting protectionist tariffs on countries and force them to make the same choice,” he says.

Long-term alternatives are needed, ones that do not impact on yields or fruit quality.

The current research programme that is investigating whether reducing sprays to just the one early one followed by non-chemical treatments such as cultivation or mowing, versus multiple sprays throughout the season began in the 2015/16 season.  Six vineyards in Hawke’s Bay and Marlborough were involved, with vineyards split into control (conventional multiple sprays) and the other half reduced herbicide where just the one spray was applied early season. The first spray went on just around bud burst in both scenarios. 

Over the two years canopy gaps as an overall measure of vine vigour were compared between the two scenarios. There were differences but they were pretty small. Sugar accumulation was compared – the result showing; “the ripening of fruit was unimpeded by allowing stuff to grow under the vines later in the season.”

There was a difference in nitrogen though in the reduced herbicide juice samples, understandably Krasnow says, as the growth under the vines is drawing on the same source of nitrogen as the vines are. 

“This resulted in a lowering of YAN in juice. However, this lower YAN can easily be dealt with by fertilisation in the vineyard as berries develop, or in the winery by adding DAP or another nitrogen source prior to fermentation.”

“The take home message is that we can let stuff grow under our vines (after set) without impacting on the yield,” he says. “I think one of the things we need to do is re-train our eyes. A little bit of stuff growing under your vines is not the end of the world.”
He says people tend to be hung up on how the vineyard looks, and that might be doing more harm than good. Think about how much water that under vine growth is taking away from the vine in a wet season. Think Marlborough 2017 and 2018, when heavy rain arrived just before harvest. The end result was split grapes and some severe disease threats.

“In a season that is rainy, having some of that stuff there could allow it to intercept some of the water so your vine doesn’t get it all.”

What the trials did show was that the early spray close to bud burst allowed the vine to grow and develop its canopy unhindered, setting it up for the rest of the season and the following one.

“We are eliminating the competition for a short time during canopy development, so we get our solar panel up and we get flowering for this year and our bunches for next year. After that a little bit of competition doesn’t seem to be a bad thing. And could be a good thing especially if we start getting more and more rain around harvest.”

It also reduces the potential of chemical residues on fruit, which given the movement against Glyphosate, is a positive thing for the future.

Could a virus help control botrytis?

Presented by Robin MacDiarmid, Plant & Food

Research has discovered a pathogen that attacks Botrytis and it could be the answer to future outbreaks of the disease, Robin MacDiarmid says.

It is all based around the development of genome sequencing, which has allowed scientists to see for the first time viruses in their initial form.

“A virus is smaller than the wave length of light,” MacDiarmid says, “so you are never going to see it. What you do see is the disease it causes. But now our genomes can be sequenced and viruses are just a little bit of genome sequence – just a little bit of software looking for compatible hardware.”

By using the power of sequencing there is the ability to look at more than just the disease pathogens cause and focus on the pathogens themselves. MacDiarmid says what they are discovering is that not all viruses are bad. 

For example, after analysing Botrytis samples from a collection at Landcare, scientists have discovered a new virus, that actually attacks the Botrytis fungus.

“We found this virus multiple times, but only the one sequence. So it is possible that there are others.”

Which leaves the scientists with a large number of questions, the number one being how can this new virus be of use?

“It has some traits that are very desirable. It reduces the rate of the growth of Botrytis and we can infect new Botrytis with this virus by spraying. Now we have a slew of questions that we need to address. How stable is it? What stage of Botrytis is it working best on? Can it protect from infection? Can it treat infection? What is its host range?”

But as MacDiamid says, it takes a very short time to ask a question. 

It takes a lot longer to address that question. In the meantime, they will continue to study the new virus and look for appropriate commercial partners to see if it can be produced in an economic way. “And to see if it is economically viable in terms of that it performs how we think it is going to perform.”

MacDiarmid says this virus is not produced through genetic engineering.

“It is found naturally from samples that have been collected across New Zealand.”

The research is ground breaking she says and hopefully will provide in the long-term the basis for chemistry free control of Botrytis.

Which after the issues this recent vintage, can’t come soon enough.

Lighter Wine Programme update

Presented by Dr David Jordan

Research of premium consumers has shown that 41 percent of our target market desire wines of lower alcohol. David Jordan says if you are in denial of that you need to wake up.

“We need to move our head from the bottom of the barrel and understand what our consumers desire.”

Sales domestically of lighter wines have grown steadily. In the total sales of Sauvignon Blanc, six percent are lower in alcohol. It is the same with Pinot Gris. In Rosé, it is slightly higher at eight percent. Sales in the export market are just beginning to grow. 

After vintage a number of large UK distributors were in Marlborough specifically asking to see wines that were lower in alcohol. There are similar stories of interest being expressed by both Australian and Canadian importers. 

“So we are seeing very positive signs in our key export markets. We believe it’s in the order of $200 million annual FOB value for our industry based on the opportunities and our assessment of them.”

The important thing to remember is that this programme is not working towards producing wines of four or five percent. Instead the wines being produced are between 8.5 and 10 percent alcohol, with the majority being at 9.5percent. “We often use the term single digit, which gives us a position in the wine stores that we wouldn’t otherwise have held.”

Producing lower alcohol wines in a natural way is paramount to consumers Jordan says. Which is why the programme has focused on managing the vineyards and the juice, rather than use technology that strips alcohol from the wine.

That is not the only reason why the Lighter Wine programme is important to the New Zealand industry. Many of the findings from the first five years of the seven-year programme are providing answers on how to deal with difficult vintages.

“Sometimes we are picking the grapes earlier than what would be considered ideal,” Jordan says. “Building tools to manage the grapes through to classy wines, with those challenges, the tools coming out of this programme are helping us to adapt.”

Climate change may lead to more rapid ripening in the future and the impact of that on our wine styles could be very real. Again, learnings from the Lighter Wine Programme could help to manage that impact.

If you would like more information on the Lighter Wines Programme, visit the nzwine.com members website.

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