Protecting Walnut Trees From Bacterial Walnut Blight
Luke Milliron is a UCANR orchard crops farm advisor for Butte, Tehama and Glenn counties in Northern California where most of the walnut blight happens. “For some folks, walnut blight, isn't even an issue depending on what their spring weather is like. Is there rain when the trees are really waking up and leafing out and unfurling,” he noted.
“Whereas for folks up in my neck of the woods, every year is it seems to be a bad walnut blight year and unfortunately it is one of those diseases that's in addition to what variety of tree you plant,” said Milliron.
There is going to be a strong spray component to managing this disease. And Milliron said that growers need to know when to spray. “That window of protection is going to be different, as to the choice of variety. “If you have an early-leafing variety, the tree will be exposed longer to more rain, with potentially more protection sprays, versus Chandler, maybe a little less,” he said.
Milliron said that copper has been the main go-to product, but walnut blight has been showing resistance to copper. “Using Mancozeb paired with copper has allowed us to have very good management of this disease. However, just as we developed resistance with copper, we're really concerned about developing resistance to Mancozeb,” he noted.