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Disease Detection and Losses

Occurrence of Aspergillus flavus in Pistachio Nuts Prior to Harvest. S. V. Thomson, Assistant Professor, Department of Plant Pathology, University of California, Berkeley, CA 94720; M. C. Mehdy, Laboratory Assistant, Department of Plant Pathology, University of California, Berkeley, CA 94720. Phytopathology 68:1112-1114. Accepted for publication 27 February 1978. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1112.

Pistachio nuts were sampled periodically from California orchards prior to harvest to determine when Aspergillus flavus infected the developing nuts and if aflatoxins were present. Aspergillus flavus was not isolated from nuts in July and from only 0.3% of the nuts in August. However, 11.8% of the nuts were infected at harvest time (15 September). The increased infection was correlated with the exposure of the nutmeat as the endocarp (shell) and often the mesocarp (hull) were split during maturation. At harvest, 28% of the insect-damaged nuts were infected with A. flavus compared to only 6% of the nondamaged nuts. When tested for synthesis of aflatoxin, 70% of the A. flavus isolates produced aflatoxin B1. However, aflatoxins were not detected in 29 samples of pistachio nuts.