Disease Note

Phythophthora porri on Onions in South Africa. P. M. von Maltitz and S. L. von Broembsen, Plant Protection Research Institute, Private Bag X5017, Stellenbosch 7600, South Africa. Plant Disease 68:732, 1984. Accepted for publication 2 April 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-732a.

In June 1982, Phytophthora porri Foister was isolated from papery white foliar lesions of bulb onion seedlings (Allium cepa L.) grown in seedbeds under sprinkler irrigation near Oudtshoorn, Cape Province, South Africa.  Affected plants appeared in patches in the seedbeds.  Isolates conformed to previously published descriptions of P. porri.  The optimum growth temperature for the fungus on cornmeal agar was 20 C.  Inoculation with zoospores caused lesions on foliage but not on bulbs or roots of 2-wk-old onion seedlings.  The fungus was reisolated from both fresh and dried-out lesions using P10VP selective medium.  To our knowledge, this is the first report of P. porri in Africa.

Reference: Tsao, P. H., and Ocana, G. Nature 223:636, 1969.