Alternaria leaf spot can occur on almond trees grown anywhere in California’s Central Valley, but rarely is it severe enough in the northern San Joaquin Valley to require treatment. It has been most serious on trees in the southern San Joaquin Valley and in the northern Sacramento Valley.
The disease occurs first and is most severe on exposed leaves. Trees trained to an open and spreading canopy usually have more severe Alternaria leaf spot.
For information on how to identify and manage alternaria leaf spot, go to the University of California-Davis IPM web site at http://www.ipm.ucdavis.edu/PMG/r3101611.html.