Grape Growers Facing Odd Year for Disease Pressures

Brian German Grapes, Industry, Nuts & Grapes

Disease pressures in vineyards are likely to be higher this year due to environmental conditions. BASF Technical Service Representative for the Southern San Joaquin Valley, Kevin Caffrey explained there is also a lot of general inoculum out there. With new leaves emerging on vines, the plants can be especially susceptible to botrytis.

Disease Pressures

“Honestly, no one’s thinking to spray a botryticide this early or any time until bloom. So, there’s a high propensity to get leaf botrytis, which is just botrytis infecting the leaf. Which in turn, when the blooms come out, becomes botrytis infecting the clusters,” Caffrey noted. “So, we are actually building for a very odd year of high botrytis incidents that we generally wouldn’t consider. Especially planning for it as early as may occur this year.”

Caffrey said some growers have been forced to make aerial applications for Phomopsis because of an inability to get a ground rig into vineyards. There has been a strong grower sentiment of feeling behind this season, with abnormal weather impacting average timing for disease management approaches. “Trying to time things to get things done has been very compressed and causing a lot of decisions that while not completely out of the norm, are definitely a little unique this year,” Caffrey explained.


Adding to the disease concerns is the high likelihood of powdery mildew being particularly problematic this year. High levels of moisture and warming temperatures in the weeks ahead will create conditions conducive to increased disease pressures. Growers are encouraged to plan ahead as it relates to the materials necessary for management.

“In a year like this, when we have to probably tank mix and probably have to spray in slightly higher intensity, we don’t want to break chemistry. So trying to do probably a three mode of action rotation is by far the best,” said Caffrey. “Outside of that, just make sure you don’t have back-to-back modes of action. You want to keep those FRAC groups separated as best you can. Keep your sulfur in rotation. Keep some copper out there because we’re going to see bacterial diseases coming up as well.”

Listen to the interview below.

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Brian German

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Ag News Director, AgNet West