Infection of Peach Buds by Botryosphaeria obtusa

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Abstract
Three species of Botryosphaeria that cause peach tree fungal gummosis, B. obtusa, B. dothidea, and B. rhodina, were isolated from dormant peach buds in central Georgia [USA]. Only B. obtusa was present in buds in significant numbers, with populations peaking in January and Febraury. Inoculations showed that both B. obtusa and B. rhodina infect and kill buds before bloom, but B. dothidea does not. Incidence of B. obtusa was greater in symptomless buds than in dead buds, indicating that infected buds often remain symptomless. Protective fungicide applied to an orchard early in January each year since planting reduced incidence of B. obtusa in buds and in subtending branches by 50% in the third year after planting, but there was no reduction in incidence in subtending twigs or in disease severity the fourth year after planting. Systematic isolations indicated that in mature, severely infected trees systemic growth of the fungi progressed as freqeuntly from older infected wood into budwood as from infected floral organs into subtending twigs. A survey of twig internodes indicated that 25% of the budwood in such trees was infected in the fall of 1984. This aggressive systemic invasion may render larger but less numerous infection sites, such as wounds, more important then buds to disease development.

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