Experiments with Biocontrol of Alternaria alternata

A biocontrol yeast (WRL-76) developed by USDA-ARS at the Western Regional Research lab was evaluated for control of Alternaria alternata on pistachio. The experiment was conducted over a four year period in a Madera Co., CA orchard. Counts of damaged vs. intact fruit clusters were taken on 100 control and treatment trees, as well as commercial yields. During two of the four years, high levels of disease were observed while little or no disease developed during the other two years. Significant differences in cluster damage were observed during the high disease years. Treated trees produced an overall but non-significant yield improvement of 6.6% for all years and an average 13% yield improvement during the 2 years of high disease incidence. Differences in % viable clusters were significant, however.  Cluster count values were significantly correlated with yields.