Shot hole encourages almond drop, doesn't harm kernels

Abstract

Severe spring outbreaks of shot hole disease are often accompanied by leaf fall and fruit drop. Although fruit are shed in response to defoliation, the direct effect of shot hole infection on developing fruit was not known. When fruit at various stages of development were inoculated with high concentrations of the shot hole pathogen, very young and midsized fruit fell, whereas older fruit were retained. Typical shot hole lesions developed on midsized fruit, and full-sized fruit became resistant to infection when embryo development began. Infection did not affect kernel weight, but caused a slight, economically unimportant reduction in kernel length.