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Effects of Deficit Irrigation on Hull Rot Disease of Almond Trees Caused by Monilinia fructicola and Rhizopus stolonifer

April 2001 , Volume 85 , Number  4
Pages  399 - 403

B. L. Teviotdale , Department of Plant Pathology , D. A. Goldhamer , Department of Land Air and Water Resources, University of California Davis, Kearney Agricultural Center, Parlier 93648 ; and M. Viveros , University of California Cooperative Extension, Bakersfield 93370

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Accepted for publication 4 December 2000.

Almond trees were irrigated from March through November 1994 and 1995 with 70, 85, and 100% of potential evapotranspiration (ETc). Deficit irrigation was accomplished by delivering 70 or 85% of ETc at every irrigation (sustained) or 50% of ETc during 1 June to 31 July (70 regulated) or 1 to 15 July (85 regulated). The natural incidence of dead leaf clusters and dead spurs, twigs, and small branches, measured at harvest, lessened with decreasing amounts of water, and regulated deficits were more effective than sustained deficits in reducing disease. Fruit at early dehiscence on trees in each of the five irrigation treatments were inoculated with 0.1 ml of suspensions of 104 spores per ml of Monilinia fructicola or Rhizopus stolonifer. Monilinia fructicola caused more hull rot than R. stolonifer, and both pathogens responded similarly to the irrigation treatments. The rate of fruit maturation was monitored for approximately 4 weeks before harvest by scoring the percent abscission and dehiscence and measuring the hull moisture content of fruit on trees in each irrigation treatment. Dry kernel weight was determined at harvest. Maturation was slower and kernel weight greater in treatments receiving 85% of ETc than 70% or those under sustained compared with regulated irrigation regimes.

© 2001 The American Phytopathological Society