Elizabeth Fichtner, a UC farm adviser for Tulare County, gave pointers on how to distinguish between thousand cankers disease and shallow bark canker, which poses mostly a cosmetic threat. She noted that thousand cankers disease is a complex requiring both a pathogen and a pest that can carry it, the walnut twig beetle.

That disease, first reported in California in 2008, has spread in recent years, and either the complex or its carrier or pathogen have cropped up in Ohio, Pennsylvania and other Eastern and Midwestern states, which have native populations of black walnuts.

The good news for exporters of walnuts is that the pathogen and insect infest the wood, not the nut itself.

Bob Beede, UC farm adviser for Kings County, talked of nutrient needs for walnuts. He said orchards in the San Joaquin Valley often face zinc deficiencies and that foliar spraying is a good way to counter that.

He said Valley growers are facing tighter regulations on nitrates in groundwater and are being urged to join water quality coalitions and can expect that they will have to come up with nitrogen management plans.