Disease Note.

First Report of Eucalyptus Dieback Caused by Nattrassia mangiferae in North America. Michael E. Matheron, Yuma Agricultural Center, University of Arizona, Yuma 85364. Lynne Sigler, Microfungus Collection and Herbarium, University of Alberta, Edmonton, Canada T6G 2E1. Plant Dis. 78:432. Accepted for publication 22 December 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0432C.

Disease symptoms including dieback of large branches, separation of phloem from xylem, and the presence of cankers exuding gum have been observed during the summer since 1985 on Eucalyptus camaldulensis Dehnh. trees in southwestern Arizona. Nattrassia mangiferae (H. & P. Sydow) Sutton & Dyko (syn. Hendersonula tomloidea Nattras) (1) was consistently isolated from the advancing margins of branch cankers. In growth chamber tests, individual 30-cm-long x 5-10-mm-diamelcr stem segments with leaves attached from E. camaldulensis, E. citriodora Hook., E. cladocalyx F.J. Muell., E. leucoxylon F.J. Muell., E. maculata Hook., E. polyanthemos Shauer, and E. viminalis Labill. were inoculated with N. mangiferae by placing a 5-mm-diameler agar disk containing the fungus into a similar sized wound, where bark and phloem tissue were removed. Stem segments were placed in 1-L flasks containing 500 ml of water and maintained in an illuminated growth chamber (39 (ΜE s-1m-2) at 30 C with a 12-hr photoperiod for 6 days. The average length of canker that developed on each of the seven tested species of Eucalyptus ranged from 36 to 91 mm. Additionally, 10-cm-long x 5-10-mm-diameter stem segments of E. camaldulensis were inoculated as above and incubated in moist chambers for 6 days al temperatures of 15, 20, 25, 30, or 35 C. The average lengths of resultant cankers were 1,5, 11, 26, and 36 mm, respectively. N. mangiferae was reisolated from cankers on inoculated stem segments. The fungus has been reported on Eucalyptus in Portugal (I), Iraq, and India, but this is the first known report of N. mangiferae on this host in North America.