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Ecology and Epidemiology

Effects of Dew-Period Temperature on Sporulation, Germination of Conidia, and Systemic Infection of Maize by Peronosclerospora sacchari. M. R. Bonde, Research plant pathologist, U. S. Department of Agriculture, Science and Education Administration, Agricultural Research, Plant Disease Research Laboratory, P.O. Box 1209, Frederick, MD 21701; J. S. Melching, Research plant pathologist, U. S. Department of Agriculture, Science and Education Administration, Agricultural Research, Plant Disease Research Laboratory, P.O. Box 1209, Frederick, MD 21701. Phytopathology 69:1084-1086. Accepted for publication 3 April 1979. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1979. DOI: 10.1094/Phyto-69-1084.

Peronosclerospora sacchari sporulated profusely on maize from 15 to 23 C. At 26 C and above, conidiophores were malformed and produced few spores. Temperatures between 15 and 30 C were equally favorable for germination in vitro. With 5-hr incubation, in a representative test, germination was 5886% between 8 and 35 C, the entire range tested. After 2 hr, spores incubated at 26 C had the longest germ tubes (average length 315 μm); germ tubes were long (>56% of maximum) from 18 to 32 C. The temperature range during the dew chamber period most favorable for infection and subsequent disease development was 1832 C (6381% infection for a representative experiment), but incidence of infection was nearly as high at 12 C (4453%). At 8 C, the lowest temperature tested, 6% of the plants became systemically infected. After inoculation by atomizing with a conidial suspension, a 4-hr dew period was as effective as an 18-hr period in inducing systemic infection. Temperature and moisture conditions favorable for infection of maize by P. sacchari are common during the growing season in much of the United States corn belt.

Additional keywords: Sclerospora sacchari, sugarcane downy mildew, epidemiology, corn.