Protect the chemistries that protect your yield

June 09, 2017

Grape Vineyard in California

This growing season many grape growers are facing heavy disease pressure due to drenching rains received over the winter months and continuing through spring. Excellent disease control is vital and, unfortunately, more applications of products on tighter spray schedules could mean an increased risk for fungicide resistance if products are not properly managed.

“Growers know the importance of product stewardship through rotating fungicides with different FRAC codes,” said Leigh Ann Harrison, Technical Service Representative for BASF. “They rely on these chemistries to protect their yield and want to be able to keep using them for many more seasons.”

There have been no reported instances of Pristine® fungicide breakdown in management of Botrytis bunch rot or powdery mildew in vineyards.

“When you do see ‘resistance’ to a material, especially in a heavy pressure season, you should check your sprayer to see if you are applying it correctly,” said Max Jehle, a Pest Control Advisor at MAX Agricultural Consultants Inc. “Many resistance problems are normally an application error that reduced the coverage of the material.”

It takes around 10 years for a new fungicide to be developed, according to BASF. That is why it is important for growers to continue practicing excellent product stewardship; the longer existing products remain effective against diseases, the longer growers have as many tools as possible to optimize yields.

Common resistance management practices include rotating chemistries in different FRAC groups to keep diseases guessing. It is also important to use fungicides preventively at their full labeled use rate. This will help ensure optimal control or suppression of the disease. Harrison suggests using the UC-Davis powdery mildew risk index to monitor the disease and determine when fungicides should be applied.

“Fungicides are most effective when used preventatively, before disease outbreaks occur,” Harrison said. “Most seasons’ applications begin at bud break with microionized sulfur and continue with sulfur or fungicides on 7- to 14-day intervals, depending on the conditions.”

Just before bunch closure is another important time to apply a powerful and effective chemistry. This helps protect the health of a crop as well as the yield quality for table grapes. Bunch closure is around the time when Botrytis bunch rot starts to appear, so applying a chemistry, such as Pristine fungicide, that controls both powdery mildew and Botrytis bunch rot, gives you control of multiple diseases in one spray.

“When applied at bunch closure, Pristine fungicide offers grape growers protection against two diseases at once, reducing the need to spray multiple fungicides for multiple diseases,” Harrison said. “Growers have been using Pristine fungicide for many years with great success.”

Pristine fungicide is a trusted and proven chemistry for many grape growers.

“You can’t cover every leaf in the canopy 100%,” said Chris Cucuk, a Pest Controls Advisor at Cucuk Consulting in California. “That’s why it is important to go in with dusting sulfur between applications and to use a systemic fungicide such as Pristine.”

The local systemicity of Pristine ensures that parts of the plant that did not receive direct treatment still have protection from diseases.

Product stewardship begins long before the first signs of fungal growth. Creating a plan for the season with your PCA and local BASF representative during dormancy allows you to choose chemistries from different FRAC groups before you are in the thick of disease pressure.

“When you have a strong fungicide program, [spraying] every 7 to 10 days with good rotation, you see a reduction in inoculant and your probability of seeing resistance is reduced,” said Hector Mariscal, an independent Pest Control Advisor at DEVAN, Inc. “The challenge is to mix chemistries and classes so we don’t get resistance and can use the tools that we have at our disposal to make a long season uneventful.”

To learn more about product stewardship and resistance management, visit www.GrowSmartGrapes.com.

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