Evaluation of Pathogenicity of Bipolaris and Curvularia spp. on Dwarf and Ultradwarf Bermudagrasses in Florida

Abstract

Isolates of Curvularia lunata, C. geniculata, Bipolaris hawaiiensis, and B. cynodontis were tested for pathogenicity on the hybrid bermudagrass cultivars Tifdwarf, TifEagle, and FloraDwarf at 20 and 30°C. Curvularia lunata, C. geniculata, and B. hawaiiensis produced some minor leaf tip necrosis at the cut ends of leaves 24 to 48 h after inoculation. Bipolaris cynodontis produced significant tip dieback and leaf spotting on all three cultivars at both 20 and 30°C, and disease severity was higher at 20°C than at 30°C. With C. lunata, C. geniculata, and B. hawaiiensis, occasional leaf-spotting occurred only on senescing, older leaves. Bipolaris cynodontis is considered pathogenic on bermudagrasses, while C. lunata, C. geniculata, and B. hawaiiensis are considered senectopathic, able to incite disease only in senescing plant tissue. Curvularia lunata and B. hawaiiensis resulted in higher disease severity at 30°C than at 20°C, indicating that these species are senectopathic at higher temperatures. Accepted for publication 29 September 2006. Published 19 January 2007.