Vol. 129 (2016): Proceedings of the Florida State Horticultural Society
Ornamental, Garden & Landscape

A New Disease Caused by a Cercospora sp on the Florida Native Tetrazygia bicolor

Florida State Horticultural Society Proceedgins 2016 Volume 129

Published 2017-05-15

Abstract

The yellowish-orange Cercospora leaf spots were observed on Tetrazygia bicolor plants in the native pine lands of Miami-Dade County, FL. The leaf spots were affecting 30% to 50% of T. bicolor in the pine land stands. The actively expanding leaf spots were necrotic. A Cercospora sp. was isolated on acidified potato dextrose agar (APDA). Ten uninfected leaves of T. bicolor were placed in each of two plastic boxes lined with damp paper towels (incubation chambers ICBC). Five leaves were treated as controls and the other five were inoculated. Leaves misted with water prior to inoculation. Control leaves were inoculated with one, 3 mm square of uninoculated RSA. Treated leaves were inoculated with 3 mm squares of seven-day-old cultures of the T. bicolor on APDA. Leaves were then misted again, covered and incubated in the ICBC at 25 °C (77 °F). After six days, all of the inoculated leaves that were showing actively expanding leaf spots which were necrotic. Cercospora was reisolated from the inoculated leaves, thus proving Koch’s Postulates.