Mysterious fungus killing Valley almond trees


Scientists have identified a fungus called Ganoderma adspersum killing almond trees from Merced to Kern counties.

Kerman almond farmer Anthony Borges says, “This disease eats the tree from the inside out. By the time you notice it, it’s already too late for the tree.”

Infected trees are said to be so weak, they suddenly snap and fall over.

Borges says, “We’re not even sure if by moving it we’re spreading the disease through the rest of the orchard or even how to get rid of it. If we need to burn it? If we need to bury it? We have no idea how to get rid of it.”

UC Davis Plant pathologist Bob Johnson came across the fungus five years ago, while interning for the state. He says, “I noticed wood decay was a problem but there was no information on it. So I decided to pursue a P.H.D. and research it.”

Johnson is in Davis writing his dissertation on the fungus — now identified as ganoderma adspersum. Little is known about how it. He says, “We’re only now at the point where we can ask how can we manage this? Previously, we were working on figuring out what is this.”

He says it likely came from Europe and is not much different from countless other ganoderma fungi in California… except this species apparently produces enzymes that can defeat a healthy tree’s defenses.

Johnson says right now nobody knows how to manage or stop it. Future research aims to learn how it spreads.

A theory he wants to test involves if below-ground wounding from mechanical shaking during harvest allows spores to infect trees. He says, “if dust is moving to your neighbor’s orchard, so are the spores that were in your orchard.”

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