Associate Professor & Extension Specialist University of Arizona Yuma, Arizona, United States
Abstract Text: Brown wood rot (BWR) is a major disease of desert lemons in the southwestern USA. It is primarily caused by the basidiomycete Fomitopsis meliae. The fungus infects young and mature lemon trees through injuries or cracks by airborne basidiospores and leads to progressive tree dieback and decline, resulting in yield reduction and premature tree mortality. A sound knowledge of the pathogen’s biology and epidemiology is crucial to develop effective disease management strategies. Data on spore inoculum production, dispersal, and the early phase of disease development are scarce. We developed a highly sensitive SYBRA Green qPCR method to quantify F. meliae spores in spore trap samples. We monitored the temporal dispersal of F. meliae and the progress of BWR in three extensively managed lemon orchards in Yuma, Arizona, in 2019 and 2020. Air samples were collected usingBurkard Multi-Vial Cyclone Samplers. Our results show that F. meliae overwinters and oversummers in infected living/dead tree branches and main stem as well as in diseased wood litter on the orchard floor. Fruiting bodies are produced only on wood litter in Yuma lemon orchards. Spore dispersal and infections occur throughout the year. Our first results describing the spore dispersal dynamics of F. meliae help understand the disease dynamics and will be a basis for improved disease forecasting models.
