The video that a pair of plant-disease researchers played for the audience at a state almond conference last month would have worried almost anyone in the business of growing Kern County's second highest-grossing crop.
It showed a man pushing against a full-grown almond tree. With seemingly little effort, the whole tree toppled.
"That kind of, like, gives people pause," said Gabriele Ludwig, who as director of sustainability and environmental affairs for the Almond Board of California was in the audience that day and watched the video. "You're not used to just touching a tree and seeing it fall over.”
The tree in the video had been infected with a fungus, originally from Europe, called Ganoderma adspersum. It rots wood from the inside out, usually resulting in weakening of the trunk at the ground level.
Maybe more frightening than the video footage was the fact that there is currently no treatment for trees infected with the fungus, though possible preventive measures are beginning to emerge.
The airborne fungus increasingly looms as a threat to Kern's $1.2 billion almond industry.
Researchers say ganoderma adspersum has been killing trees young and old across the southern Central Valley since it was first discovered in the area about five years ago.
It's unclear how many cases of infection have been confirmed locally. But of three kinds of ganoderma fungus infections identified recently in California almond orchards, University of California researchers say 94 percent of the cases were of the adspersum variety.
Several UC researchers actively studying the fungus could not be reached for comment Wednesday. But their public materials indicate some instances of infection have been identified in Kern.
The researchers have reported that adspersum is the most damaging of the three types of fungi, killing trees as young as 4 years old. They say the infections have resulted in the removal of orchards at less than half their 20- to 25-year life span.
"We are seeing those trees collapsing at 11, 12, 15 years old, ” said orchard systems advisor Mohammad Yaghmour with the UC cooperative extension in Kern County.
Spraying for the fungal disease has not proved effective, Ludwig said. She added that the fungus is of particular concern for growers for different reasons.
"It infects better, it grows faster,” she said. "Where we are now is, where we start to look for it, we find that it’s more widespread than anybody thought.”
With industry-funded research continuing, she said the best hope is that researchers will find a vulnerability within the fungus, possibly leading to a chemical or biological treatment.
In the meantime, Ludwig said growers might want to reduce the intensity at which they shake trees during the annual almond harvest, because rattling them too hard can open cracks that allow the fungus to enter the tree.
Another possibility, she and Yaghmour agreed, is that researchers will identify a suitable root stock that is resistant to the fungus.