University of California Cooperative Extension (UCCE) tree nut farm advisor David Doll’s PowerPoint photos of almond trees with severe cases of wood canker-caused trunk diseases are enough to make plant pathologists gleam and growers snarl.

The canker photos are very colorful but signal financial losses, in some cases large amounts, for California almond growers.

“For the growers who lose 30 percent of their trees and income to wood canker diseases it is a severe problem. They are trying to find a way to manage it,” Doll said.

Based in Merced County, Doll has developed data which links an increase in canker-based almond trunk disease to today’s modern cultural practices in almond orchards.

Doll discussed trunk diseases of almond in Tucson, Ariz. in late June during the Caribbean and Pacific Divisions meeting of the American Phytopathological Society, attended by about 130 plant pathologists and industry representatives.

Doll, and a handful of other UCCE tree nut farm advisors, author of The Almond Doctor website on a wide range of almond, walnut, and pistachio-related issues.

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During the APS meeting, Doll discussed canker disease, its negative impact on trees and grower bottom lines, and cultural changes which can reduce losses.

For years, three primary pathogens have taken dead aim at almond tree scaffolds - ceratocystis canker, band canker, and aerial phytophthora.

These pathogens cause infection of the trunk or the primary scaffolds which can lead to scaffold decline, tree death, and crop loss. Growers have enacted management techniques based on weather conditions and reducing damage to infected trees during harvest.