Vol 120 (2007): Proceedings of the Florida State Horticultural Society

Plectosporium blight of cucurbits

Gary K. England
University of Florida
Published December 1, 2007
  • Microdochium tabacinum,
  • Fusarium tabacinum,
  • zucchini,
  • diamond-shaped white to cream-colored lesions


Plectosporium blight of cucurbits, caused by the fungus Plectosporium tabacinum (formerly known as Microdochium tabacinum and Fusarium tabacinum), is a relatively new disease of cucurbits that was first reported in Tennessee in 1988. Henceforth, it has been observed in numerous eastern states, causing significant damage in commercial plantings of summer squash, pumpkin, and some gourd cultivars. Trials conducted in various states showed a 50% to 85% loss of marketable fruit attributed to this disease. Symptoms of Plectosporium blight of cucurbits are diamond-shaped white to cream-colored lesions on the petioles and underside of the leaf blades. In severe infestations, the lesions on the petiole will coalesce, causing the petiole to become brittle and susceptible to breakage. The first reported observations of Plectosporium blight of cucurbits in Florida were made in Fall 2005 on two farms producing summer squash in Sumter County. This disease was observed in both yellow squash and zucchini, with the most severe symptoms expressed in the latter. Recommended tactics for the management of this disease in Sumter County included crop rotation, scouting, and fungicide treatments.