NPDN 2007 Meeting - Biology and diagnosis of Philippine downy mildew

NPDN National Meeting 2007

Poster Abstract

Biology and diagnosis of Philippine downy mildew

Authors: JAN M. BYRNE (1), Ray Hammerschmidt (2)

Affiliations: (1) Diagnostic Services, Michigan State University, East Lansing, MI; (2) Dept. of Plant Pathology, Michigan State University, East Lansing, MI

Philippine downy mildew caused by Peronosclerospora philippinensis has not been reported in the U.S. This pathogen is currently on the list of USDA PPQ Select Agents and Toxins. The pathogen causes significant economic losses in China, India, Indonesia, Japan, Nepal, Pakistan, and Thailand. P. philippinensis infects corn, sorghum, sugarcane, and some weedy grass species. Young plants are infected by soil borne spores that persist in saturated soil. Improperly dried seed can also serve as a source of inoculum. Infected plants have chlorotic streaks may be stunted and have a wilted appearance. Infection may result in deformed tassels and infected ears do not develop properly. Spores produced on the underside of infected foliage are easily wind borne and serve as a source of secondary inoculum. Disease increases with increasing annual rainfall; production of conidia requires free moisture. Differentiation of P. philippinensis and other closely related oomycetes is difficult. NPDN diagnosticians will need training and detailed diagnostic resources to distinguish these fungi. Molecular diagnostic assays to identify this pathogen are not yet available.

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