California’s abnormal spring weather has resulted in an increase in botrytis presence, particularly in the San Joaquin Valley where severe incidences have been reported in vineyards. There are some cultural practices that can be implemented, as well as various materials available that help to mitigate infection.
“There are a lot of fields affected by botrytis,” said Gabriel Torres, UC Viticulture Farm Advisor for Tulare and Kings counties. “It is something that we expected having that amount of rain that late in the season. That’s like the perfect storm to develop botrytis outbreaks.”
Botrytis is typically associated with bunch rot; however certain environmental factors can create conditions resulting in damage to other areas of the plant. The cool, damp spring created circumstances that increase the chances of leaves, tendrils, canes, and immature clusters to become infected.
As the pathogen requires moisture to develop, Torres suggests implementing practices that help to lower the humidity and free water on tissues. It is important to note however that canopy management actions to increase airflow and light penetration need to be performed carefully so as not to allow sunburn. “It’s effective not only to guarantee a drier condition but also better penetration of any fungicide that is applied,” Torres noted.
Whether it is organic or conventional production, Torres said there are multiple options available that can help with addressing botrytis presence in vineyards. “There is also different fungicides that can be applied. My recommendation is to visit the UCANR IPM webpage, so growers can see different options,” said Torres.
Growers should consider the issue of fungicide resistance as materials are being considered for application. “Botrytis is a very common pathogen in different crops. Most of the crops that we have in the valley are susceptible to botrytis,” said Torres. “If we don’t do a good rotation of fungicides, we can create the condition when the pathogen doesn’t respond to the fungicide that we apply.”
Listen to Torres’ interview below.