Powdery Mildew Caused by Erysiphe cichoracearum on Five New EucalyptusHosts in Arizona. M. E. Matheron, Yuma Agricultural Center, University of Arizona, Yuma 85364. J. C. Matejka, Yuma Agricultural Center, University of Arizona, Yuma 85364. Plant Dis. 76:1077. Accepted for publication 9 July 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-1077D.
In February 1992, conidia and mycelia of powdery mildew were
observed on I-yr-old plants of Eucalyptus cladocalyx F.J. Muell.,
E. viminalis Labill., E. camaldulensis Dehnh., E. leucoxylon F.J.
Muell., and E. polyanthemos Schauer growing in a greenhouse in
Arizona. E. citriodora Hook., E. globulus Labill., and E. maculata
Hook. plants of the same age in the same greenhouse showed no
symptoms of the disease. Both sides of leaves of affected plants were
covered with mycelia and conidiophores. The ellipsoid conidia were
in chains, did not contain fibrosin bodies, and conformed to those
of Erysiphe cichoracearum DC. At the time symptoms appeared,
maximum and minimum temperatures in the greenhouse were 32.5
and 16.3 C, respectively. This pathogen has been described on 11
species of Eucalyptus growing in greenhouses in California (1), but
this is the first report of E. cichoracearum in the United States on
the species of Eucalyptus named here.