J.C. Comstock and R.A. Gilbert2 1. This document is SS-AGR-203, one of a series of the Agronomy Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First printed March 1991. Revised December, 2009. This publication is also a part of the Florida Sugarcane Handbook, an electronic publication of the Agronomy Department. For more information you may contact the editor of the Sugarcane Handbook, R.W. Rice (email@example.com). Please visit the EDIS Web site at http://edis.ifas.ufl.edu. 2. J. C. Comstock, research plant pathologist, USDA-ARS, Sugarcane Field Station, Canal Point, FL and Robert A. Gilbert, associate professor, Everglades Research and Education Center--Belle Glade, FL, Florida Agricultural Research Stations, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611. The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition. Eye spot has been reported in many sugarcane-growing areas of the world. Eye spot is a minor disease because almost all varieties are resistant, even without any selection or screening program for resistance. A rare susceptible variety may have severe economic losses if environmental conditions are favorable. In one case, a 33% loss in cane tonnage was documented. Eyespot was observed in a few growers' fields in 2004, but it is not a problem for Florida growers at this time, thus only the most important features of the disease will be described. Typical mature eye spot symptoms are characterized by a reddish-brown elliptical lesion (0.5 4.0 mm long, 0.5 2.0 mm wide) with yellowish-brown margins (Figure 1). Reddish-brown to yellowish-brown streaks, sometimes called "runners," extend upward from individual lesions toward the leaf tip. These streaks are 3 6 mm wide and 30 90 cm long. Multiple lesions can be extensive. The runners occur only in cooler temperatures and are not present in hotter temperatures. ( Figure 2). Eye spot lesions and runners on sugarcane leaves.
Sugarcane Eye Spot Disease 2 Multiple eye spot lesions with runners in the field. Eye spot disease is caused by the fungus Bipolaris sacchari. Eye spot is transmitted by spores, which are produced abundantly on leaf lesions and are dispersed by wind and rain. Fungal spore germination is favored by high humidity and dew formation. Colonization is more rapid in younger leaves than older leaves. Transmission by seed piece does not occur. Mechanical transmission by equipment and by human activity is not an issue. The only practical and efficient method for controlling eye spot disease is with resistant clones. Resistant clones can be grown without losses, even in environments that favor eye spot disease. Chemical control using foliar fungicides is not practical.