ISHS Acta Horticulturae 470: II International Symposium on Pistachios and Almonds
SPREAD OF BOTRYOSPHAERIA DOTHIDEA IN CENTRAL CALIFORNIA PISTACHIO ORCHARDS |
| Authors: | Themis J. Michailides, David P. Morgan, D. Felts |
| Abstract:
Botryosphaeria panicle and shoot blight of pistachio, caused by the ascomycete Botryosphaeria dothidea, was first reported in California in 1984 in several orchards in Butte, Glenn, and Tehama Counties of the Sacramento Valley. Botryosphaeria blight, a devastating disease, reduces yields and kills fruiting buds and wood. In 1995 and 1996 a total of 70 commercial pistachio orchards located in the Sacramento and the San Joaquin Valleys were surveyed to determine the spread of Botryosphaeria blight in California. Twenty to 35 blighted shoots, rachises, and leaf petioles that were retained on the trees from the previous year were collected arbitrarily from six to eight rows in each orchard. The samples were examined with a dissecting microscope for the presence of pycnidia of B. dothidea. Botryosphaeria dothidea was found in 70% (1995) and 52% (1996) of the commercial pistachio orchards surveyed, in 5 to 100% of the blighted shoots and in 5 to 90% of the blighted rachises for the various orchards. Other fungi recovered from these samples were species of Phomopsis and Camarosporium, which can also cause shoot blight in pistachios. In addition, in three orchards where Botryosphaeria blight was very common, we sampled blighted shoots from several wild and cultivated species growing close to these pistachio orchards. Samples of eight of the 12 species sampled had pycnidia of B. dothidea. These results suggest that Botryosphaeria blight has become widespread and caused yield losses in many California counties. None of the samples collected from Kern County, where most of the pistachio acreage is located, had any signs of Botryopshaeria. Possible ways by which the disease spreads will be discussed. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
