Friday, 01 May 2015 14:30

Are You On Target?

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David Manktelow explains the efficacy of correct spray techniques.  Photo Gisborne Herald. David Manktelow explains the efficacy of correct spray techniques. Photo Gisborne Herald.

The performance of a variety of sprayers was put to the test at a workshop in Gisborne earlier this year.

Facilitated by scientist Dr David Manktelow, the “Are you on target?” seminar looked at three canopy sprayers to assess spray coverage and penetration, and compare performance. Dr Manktelow focused on sprayer set-up and tested the accuracy and effectiveness of spray application through the use of water-sensitive papers which measured the way spray penetrated the canopy and covered the leaves.

“Powdery mildew disease has been a problem on vineyards around the country in recent seasons, with some vineyards in particular having trouble controlling the problem,” said Dr Manktelow.

“As with most diseases, the problems that have been experienced cannot be attributed to a single cause. Likewise effective and sustainable disease management requires that vineyard managers get a series of management steps right. Case studies on vineyards that have experienced problems with powdery mildew have usually identified different combinations of possible causal factors.” 

The most common management factors that need to be considered have been (in any combination and not in any particular order):

1. Avoid excessively-long intervals between spring and post-bloom fungicide applications - intervals of over 21 days are often seen in spray diaries.The powdery mildew pathogen infects young green tissue and long intervals between sprays will not guarantee protection.

2. Ensure you are applying an appropriate chemical application rate -intensively-planted vines on narrow-row spacings require more chemical per hectare than equivalent vines on wider-row spacings. 

3. Set up your sprayer to achieve effective coverage, especially of bunches in the fruiting cordon. Fruit are often under-dosed and a greater proportion of the sprayer output should be directed to the fruiting zone.  

4. Manage your canopies to avoid excessive vigour and density and maximise potential spray coverage. 

5. Don’t rely too heavily on DMI fungicides - there is some real concern about resistance development to fungicides within this chemical group on at least some vineyards.      

Improving sprayer set-up and delivery is one of several different important steps that growers can take towards improving disease control outcomes, Dr Manktelow said. But the news was not all bad.

“The good news is that checking sprayer performance is quick to do and tuning your sprayer as your canopies develop during the season almost always delivers an improvement in coverage,” he said.

 “And the really good news is that the integration and improvement of different powdery mildew management techniques on vineyards that were badly affected in 2013-14 has seen a significant turnaround in 2014-15 with some of the worst-affected blocks now looking forward to a great 2015 harvest.”

Being practical and hands-on meant the seminar was highly successful, said Al Knight, Gisborne Wine Growers Association President. 

“David was really surprised at the variability of the spray application on our vineyard, and that comes down to the set-up of our spray equipment,” said Knight who manages the Vigneto Vineyard.

“It demonstrated we are not being as effective with our spray coverage as we assume, and the changes suggested will increase that effectiveness by at least 20 percent. There’s no doubt it helped growers better understand the efficiencies around spray application. The technique is not as widely-used as it could be and I think after our workshop, there will more growers using the papers.”

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