The Relationship Between Date of Hull Splitting and Decay of Pistachio Nuts by Aspergillus Species. M. A. Doster, Department of Plant Pathology, University of California, Davis, Kearney Agri-cultural Center, 9240 S. Riverbend Ave., Parlier, Calif. 93648. T. J. Michailides, Department of Plant Pathology, University of California, Davis, Kearney Agri-cultural Center, 9240 S. Riverbend Ave., Parlier, Calif. 93648. Plant Dis. 79:766-769. Accepted for publication 18 April 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0766.

Atypical pistachio (Pistacia vera) nuts that have split hulls, known as "early splits," frequently have kernels decayed by Aspergillus spp. In 1992 and 1993 pistachio nuts that had split hulls were marked in commercial orchards at approximately 2-week intervals. Depending on the or-chard, 15 to 48% of the early splits had formed more than 4 weeks before harvest and 10 to 30% formed within 2 weeks before harvest. At harvest these nuts were also evaluated for ker-nel decay, insect infestation, and several physical characteristics. The incidence of decay caused by Aspergillus spp. (predominantly Aspergillus niger) was three times greater in the oldest early splits than in early splits formed in the period before harvest (no decay was found in normal nuts with nonsplit hulls). The oldest early splits also had the most shriveled hulls, which is a feature associated with aflatoxin contamination. At harvest the oldest early splits had less fruit fresh weight, lower kernel moisture, smaller shells, and more shell discoloration compared with early splits formed in the period before harvest and with normal nuts. These characteristics could be used to remove decayed nuts during processing.

Keyword(s): Aspergillus flavus, Aspergillus parasiticus