David Doll3 CommentsJanuary 1, 2015Diseases

Bacterial Spot of Almond in California: Update on the Disease and Management

written by Dr. Jim Adaskaveg (UC Riverside), Brent Holtz (UCCE San Joaquin), Roger Duncan (UCCE Stanislaus), and David Doll (UCCE Merced).   In the spring of 2013, we reported a high incidence of bacterial spot in some Sacramento and northern San Joaquin Valley almond orchards, especially on the ‘Fritz’ variety.  It was also found on ‘Nonpareil’, ‘Butte’, ‘Carmel’, ‘Monterey,’ and ‘Price’ but at much lower levels.  The disease has not been found in orchards in the southern San Joaquin valley. Bacterial spot is caused by Xanthomonas arboricola pv. pruni and has also been referred to as bacteriosis, bacterial leaf spot, or bacterial shot hole. Bacterial spot occurs on leaves, twigs, and fruit of almost all Prunus spp.  The pathogen commonly causes bacterial spot of peach in the eastern United States and is one of the major foliar diseases in high rainfall years. On almonds, it is a significant problem in Australia because of mid-season rain events.  In 2014, we verified the presence of the disease at previous and additional locations in California, although at levels much lower than in 2013.

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David Doll6 CommentsApril 3, 2014Diseases

Leaf Spot on Padre, Other Varieties

Odd leaf symptoms on several different varieties have been reported across the valley. Predominantly found on Padre, they are found on the edge or the tip of the leaf. The lesions can be quite large, but tend to have a watersoaked margin and a yellow halo. In other varieties, the lesion has a shot-hole-like appearance, but fruiting bodies are not visible. Farmers have complained that fungicide spray programs have not been effective in controlling this disease.

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Roger Duncan13 CommentsJune 26, 2013Diseases

Bacterial Spot – A New Disease of Almond in the San Joaquin Valley

Written by: Roger Duncan, Brent Holtz, David Doll and Themis Michailides Earlier this spring, we received reports from growers and pest control advisors that they had observed a few San Joaquin, Stanislaus and Merced County almond orchards with large amounts of amber-colored gum balls exuding from the hulls.  The damage has been predominantly on ‘Fritz,’ but there are reports of similar damage on ‘Monterey’ and ‘Padre.’  In some orchards, Fritz is severely affected while the Nonpareil and other pollinators are very clean. 

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David Doll6 CommentsJune 6, 2013Diseases

Bacterial Spot on ‘Fritz’

Written by Brent Holtz, David Doll, Roger Duncan, and Themis Michailides We have visited and received samples from orchards in the counties of Merced, Stanislaus, and San Joaquin Counties that have been experiencing symptoms of amber colored gum exuding from almonds. The damage has been predominantly on the variety ‘Fritz,’ but reports are coming in of similar damage on ‘Monterrey’ and ‘Padre.’

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