Leaf Spot Disease of Spinach in California Caused by Stemphylium botryosum.

Beginning in 1997, a new disease of spinach was found in the Salinas Valley, Monterey County, CA. Initial symptoms were leaf spots that were 2 to 5 mm in diameter, circular, and gray-green in color. Spots later enlarged, turned tan in color, and became dry and papery in texture, resembling phytotoxicity due to agrichemicals. Although fungal signs were generally absent from the spots, Stemphylium botryosum was consistently isolated and caused identical symptoms when inoculated onto 20 spinach cultivars. Three isolates did not cause disease symptoms when inoculated onto other crop plants representing 16 different genera and a Chenopodium weed species. A fourth isolate showed similar results with the exception of small leaf spots occurring on inoculated fava bean. Isolates produced a Pleospora herbarum teleomorph after 7 months incubation at 5°C. Preliminary experiments with cell-free culture filtrates indicated that phytotoxins apparently were not produced by these isolates. This is the first report of a foliar spinach disease caused by S. botryosum.

[1]  J. Correll,et al.  Economically Important Diseases of Spinach , 1994 .

[2]  S. Koike.  First Report of Spinach Anthracnose Caused byColletotrichum dematiumin California , 1993 .

[3]  N. Shishkoff,et al.  Etiology of Stemphylium leaf blight of onion. , 1989 .

[4]  J. Irwin,et al.  Taxonomic Studies on Australian Isolates of Stemphylium spp. And Associated Teleomorphs , 1986 .

[5]  W. Cowling.  Biotypes ofStemphylium botryosumon Alfalfa in North America , 1981 .

[6]  W. Cowling,et al.  Influence of the pathogen on disease severity in Stemphylium leaf spot of alfalfa in California. , 1980 .

[7]  R. Webster,et al.  The host pathogen interaction of alfalfa and stemphylium botryosum , 1976 .

[8]  G. Strobel,et al.  Isolation and Characterization of Stemphylin, a Chromone Glucoside from Stemphylium botryosum. , 1975, Plant physiology.

[9]  G. Strobel,et al.  Isolation and Partial Characterization of Four Host-specific Toxins of Helminthosporium maydis (Race T). , 1974, Plant physiology.

[10]  C. M. Leach.  Regulation of perithecium development and maturation in Pleospora herbarum by light and temperature , 1971 .

[11]  E. G. Simmons,et al.  Perfect states of Stemphylium. , 1969, Mycologia.

[12]  E. G. Simmons,et al.  Typification of Alternaria, Stemphylium, and Ulocladium. , 1967, Mycologia.

[13]  Y. Cohen,et al.  A new tomato foliage disease in israel caused by stemphylium botryosum , 1966 .

[14]  S. Wiltshire.  The original and modern conceptions of Stemphylium , 1938 .