by David Davies, Specialty Crops Marketing Manager, Arysta LifeScience

What should grape growers keep in mind this summer season?

Grape growers know that their vineyards require a lot of attention, but summer is a time to be extra mindful of disease pressures. The warm temperatures bring a higher chance for grapes to catch and spread disease. Under the right conditions, Botrytis can be particularly troublesome.

Fruit flies can help spread Botrytis spores on their bodies from plant to plant. The fungal infection colonizes on the surface of plant tissue and invades the top layers of epidermis cells. The invasion can cause epidermal cracks, where fungal growth produces mycelium and spores, resulting in the gray, velvety appearance of infected grapes. The end result is the potential for extensive decreases in plant growth, crop yield and fruit quality.

What should grape growers be doing right now?

Now that we are well into the growing season, grape growers should be walking through their vineyards scouting for any sign of disease. Botrytis can first appear anytime between April to June; however, that doesn’t mean the battle is over yet. It is often forgotten that Botrytis is a threat during all seasons, especially if the vineyard has experienced damage from hail or birds. There’s a chance infection may still be actively sporulating.

Secondary diseases, like Powdery mildew, can still be actively sporulating as well. It is advised to continue actively scouting your vineyards throughout the month of July, to be certain you are not overlooking an outbreak.

The University of California Integrated Pest Management Program provides detailed recommendations for scouting and treatment for Botrytis and Powdery mildew. When a treatment is needed, UCal recommends alternating fungicides with different modes of action within the season.

Why is mode of action so important?

Alternating modes of action helps prevent pathogen populations from developing resistance to classes of fungicides. The mode of action (MOA) you are using can also be the difference between a healthy vineyard and a Botrytis outbreak. It is important to think about the classes of fungicide available when building your resistance management plan for the season. These classes have different modes of action and will each treat the fungus differently.

Arysta LifeScience recommends rotating fungicides with different modes of action for the most effective method of resistance management. PH-D® is a FRAC Group 19 fungicide with a unique mode of action, making it an ideal addition to a rotational management program to aid in resistance management. It works by preventing cell wall construction via chitin inhibition by enzyme interference; this MOA makes PH-D especially important in rotation when multiple applications are required to fight Botrytis.

ELEVATE® is a member of the FRAC Group 17 fungicide class, making it an excellent fit in resistance management plans. This product is a protectant fungicide that binds with the waxy layer of the grape plant tissue. In turn, it disrupts the Botrytis life cycle from spore germination to the beginning of mycelial growth and colonization. This results in excellent disease control when applied preventatively.

What is your recommended plan of action for in-season disease management?

There are three fungicides from Arysta LifeScience that work together to eliminate Botrytis and Powdery mildew: VITICURE®, PH-D® and ELEVATE® Fungicides.

VITICURE is an economical and highly effective fungicide that helps break the infection cycle. The fungicide provides both preventative activity and curative action on fruit that is already showing the first signs of Powdery mildew. VITICURE is a unique imidazole, with no known cross-resistance to other triazoles in the demethylation inhibitor (DMI) group of fungicides classified as Group 3, making it an ideal member of your resistance management program. Its 7-day PHI offers flexibility to apply even late in the growing season, and it can be tank-mixed with PH-D or ELEVATE for enhanced activity against Powdery mildew and Botrytis.

PH-D is a broad-spectrum fungicide with a 0-day pre-harvest interval in grapes. It should be applied preventatively in grapes, up to three times per year, when climatic conditions exist for the development of Botrytis and other disease infection, such as Powdery mildew.

Lastly, ELEVATE is a protectant fungicide that binds with the waxy layer of the grape and disrupts the Botrytis life cycle from spore germination to the beginning of mycelial growth and colonization. ELEVATE delivers dependable and economical Bunch rot control when used in a tank-mix or rotation with other fungicides.

You can count on Arysta LifeScience for a complete line of grape protection and a staff dedicated to keeping your vineyard going strong. Contact your retailer or Arysta LifeScience sales representative for additional information, or visit www.arysta-na.com.

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