Does your orchard have Ganoderma root and butt rot?

Bob Johnson, UC Davis Plant Pathology

Wood decay fungi are ever present in orchard systems, and most species of wood decay fungi pose little threat to the overall productivity and longevity of an almond orchard. Ganoderma on the other hand, is a fungal genus that contains a few species that are known to be pathogenic on young trees and can limit the productivity and longevity of an orchard do to early tree mortality. For instance 120 acres of 9th and 10th leaf almond in Kings County were recently removed because Ganoderma root and butt rot resulted in nearly 40% of the trees succumbing to windfall over a 3 year period.

In order to better understand the incidence and severity of Ganoderma and other wood decay fungi in California almonds we need your help.  Ganoderma infection often is symptomless until the tree falls over (Figure 1), but one easy to spot sign is the presence of the fungal fruiting body, called a conk, near the base of the tree (Figure 2). Ganoderma conks are perennial and can vary greatly in size; rusty colored spores can often be seen under and around active conks.  If you have experienced decay related windfall or have seen conks in your orchard please consider contacting us to come take a look. Understanding the distribution and incidence of Ganoderma infections will help us to develop management strategies to limit the impact of this potentially damaging disease.  

Please contact Bob Johnson at 530-302-6301 or bobjohnson@ucdavis.edu if you are interested.

Figure 1. Windfall caused by Ganoderma root and butt rot.

Figure 2. Ganoderma conks. Notice rusty red colored spores around conk in bottom right picture.