Band canker

Confirmed band canker infections are on the rise in California Almonds in recent years and can be particularly damaging to 1- to 5-year-old trees. While there is no known chemical cure, growers can take steps to protect young trees from infection through cultural practices.

Canker is a disease caused by eight species of Botryosphaeria that infect young trees under 5 years old through pruning wounds and growth cracks. Infections can also be caused by shaker injury or wind cracks at the base of scaffolds, which can cause them to break.

UC plant pathologist Themis Michailides says growers should check orchards for signs of infection. Blackened gumming on trunks indicates previous infections of canker, while new infections will produce amber-colored balls of gumming in trunks or scaffolds of trees.

 

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Michailides said since there are no chemical controls for canker, focus should be on preventing infections from starting, and when you see signs of infection, removing infected limbs. A simple prevention strategy in young orchards is to make sure sprinklers do not wet trunks of trees.

“If you have sprinklers, installing a splitter that prevents wetting trunks can reduce infection by 50%,” Michailides said. “Infected limbs should be removed, and when you decide to remove an infected tree, you should remove the entire tree; don’t leave stumps or diseased wood in the orchard, as these are a source of spore inocula.”

He also recommends avoiding shaker wounds and pruning when conditions are dry, and avoiding pruning near a rain event. Disease occurs more near riparian areas such as rivers, canals and sloughs. Pruning here first provides an opportunity to spot initial infections.

Generally, Michailides said, when canker infections appear in the trunk of 1- to 5-year-old trees, the tree has a 50-50 chance of survival. If the foliage of an infected tree looks green and healthy, the tree will survive; if the foliage looks chlorotic, it is likely the tree will not survive. Growers will have to decide whether to remove the infected tree or wait and see.