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Disease Note.

Root and Crown Rot on Nursery-grown Mango Trees Caused by Phytophthora palmivora. M. E. Matheron, University of Arizona, Yuma Agricultural Center, Yuma 85364. J. C. Matejka, University of Arizona, Yuma Agricultural Center, Yuma 85364. Plant Dis. 74:530. Accepted for publication 29 April 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0530C.

In 1987, a shipment of mango (Mangifera indica L.) trees from a nursery contained several plants that had symptoms of crown and root rot before being planted in the field. Phytophthora palmivora (Butler) Butler was isolated from decayed rootlets and from potting mix of affected plants. Species identification was based on cardinal temperatures for vegetative growth, sporangium morphology, length of sporangial stalk, and oospore production. Inoculation studies using zoospores showed that this fungus was highly virulent to mango seedlings and caused root decay and eventual plant death. Rough lemon, sweet orange, and chili pepper seedlings inoculated with the pathogen did not become diseased. The introduction of P. palmivora into Arizona could be a threat to mango but not to citrus or pepper production. This is the first knowo report of P. palmivora on mango in the continental United States.