Effect of Water Stress in Cypress on the Development of Cankers Caused by Diplodia pinea f. sp. cupressi and Seiridium cardinale. Z. Madar, Department of Forestry, Land Development Authority, Qiryat Hayyim, Israel. Z. Solel, and M. Kimchi. Department of Plant Pathology, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. Plant Dis. 73:484-486. Accepted for publication 23 November 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0484.

When greenhouse-grown cypress seedlings were predisposed to extreme water deficit (psi of –4.5 to –5.5 MPa) before or after inoculation, the expansion of Diplodia cankers on stems was enhanced. None of the water deficit regimes affected the development of Seiridium canker. Under summer field conditions, the development of Diplodia canker on stems and branches was enhanced in nonirrigated plants, compared with surface-irrigated ones. The expansion of Seiridium cankers on branches, however, was markedly decreased by the water stress. These results implicate drought as a factor contributing to outbreaks of Diplodia canker during the unseasonably dry years of 1984–1986.