Keeping Vineyards Free of Botrytis Problems

Winegrowers are regularly confronted with botrytis problems in their vineyards every year. Although the disease is more prevalent in cooler growing regions, it can be a problem for any grower given the right environmental conditions. Katie Driver, technical services manager for Northern California for UPL, said growers keep several factors in mind when considering the potential for botrytis infection.

“This can become a problem in high humidity conditions associated with high nitrogen levels or tight bunches. All of this can favor an outbreak of botrytis. Infections are going to be more severe when the relative humidity in the canopy exceeds 92 percent, free moisture is present on the surface of the fruit, and temperatures are between 58 and 82 degrees Fahrenheit,” Driver explained. “Berries that have been damaged by insects, birds, machinery or other things can become infected any time after the fruit begins to ripen, as the juice from the berry can provide the water and nutrients necessary for fungal growth.”

Condensed bunches contribute to botrytis problems in vineyards in multiple ways. Grapes can crack under pressure, allowing the fungus to grow at the point of injury, which provides a moist habitat for spore germination. Cracked grapes can also attract fruit flies. The insects can then spread the disease by moving from cluster to cluster. Driver explained that they have several different options that can help growers with botrytis issues.

“PH-D is the first. It is a trusted fungicide that provides effective control with a unique mode of action that has become an important resistance management tool for stubborn diseases of grapes in addition to other key California crops,” said Driver. . “We also offer ELEVATE, which is a unique mode of action. It has a narrower spectrum of control, but is botrytis specific and there is no cross-resistance between other botrytis fungicides or SBI classes.

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