According to Themis J. Michailides, plant pathologist at the University of California, Davis, this disease, panicle and shoot blight of pistachio, was first discovered in 1984 in a commercial orchard in the northern Sacramento Valley and has since become a disease of major importance for pistachios grown in California. "Yield losses from 40 to 100 percent were not uncommon in the orchards where the disease was discovered," said Michailides. "The destruction caused by this disease makes panicle and shoot blight the most serious threat to pistachio trees grown in California," he said.
Panicle and shoot blight is caused by Botryosphaeria dothidea, a fungus that causes diseases that are aggressive and very difficult to control. According to Michailides, the pistachio industry in California is based on a cultivar that is very susceptible to this particular fungus. "Because of the California pistachio's susceptibility to this fungus, panicle and shoot blight has the potential to reach epidemic levels in pistachio orchards in only a few years," he said.
To prevent such epidemics from occurring, and since some resistance to the disease exists in the present Pistacia germplasm, breeders need to work closely with plant pathologists to develop disease resistant varieties of the pistachio tree. In addition, Michailides also recommends growers remain proactive in their efforts to keep their orchards free from infection of the pathogen by conducting regular surveys, sanitation by pruning of possible infections, controlling insects, and following fungicide programs that were shown to control panicle and shoot blight.
More on this subject is available in this month's APS feature article on the APS website at www.apsnet.org. The American Phytopathological Society (APS) is a non-profit, professional scientific organization dedicated to the study and management of plant disease with 5,000 members worldwide.
Note to editors: To receive accompanying photos, please contact APS at asteigman@scisoc.org or 651-994-3802.