Host Range of Itersonilia perplexans and Management of Itersonilia Petal Blight of China Aster

Abstract

Isolates of Itersonilia perplexans were tested for pathogenicity on 14 different plant species. Isolates from China aster and sunflower were each pathogenic to the other host and both isolates were pathogenic to chrysanthemum and gerbera, causing moderate to high incidences of flower or seedling blight in these hosts. China aster and sunflower isolates were not pathogenic to burdock, but an isolate from burdock was pathogenic to florists' chrysanthemum and gerbera. In a survey of weed species near a cut-flower production facility in southwest Florida, I. perplexans was found in only one weed species, Emilia fosbergii. However, two isolates from this weed host produced severe petal blight symptoms when inoculated onto China aster. Myclobutanil, potassium bicarbonate, and propiconazole were highly effective in reducing disease severity of petal blight in China aster, while azoxystrobin reduced disease moderately in fungicide evaluation trials. Accepted for publication 28 July 2006. Published 18 October 2006.