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Publication #SS-AGR-256

Sugarcane Yellow Leaf Disease1

J. C. Comstock, H. S. Sandhu, and D. C. Odero2

Sugarcane Yellow Leaf was first recognized as Yellow Leaf Syndrome during the 1980s in Hawaii. Later it was reportedly associated with yield losses of 25% or more in the cultivar SP 71-6163 in Brazil. Subsequently the virus sugarcane Yellow Leaf Virus (SCYLV) was discovered to be associated with the disease. Yellow leaf has been found in numerous countries of the world. However, somewhat confusingly, another disease, “leaf yellows,” has been found in other areas. Although it has similar symptoms, it is caused by a phytoplasm rather than a virus. To date, this phytoplasm pathogen has not been identified on sugarcane in Florida.

Symptoms

Symptoms of SCYLV are a yellowing of the leaf midrib on the underside of the leaf. The yellowing first appears on leaves 3 to 6 counting down from the top expanding spindle leaf (Figure 1). Yellowing is most prevalent and noticeable in mature cane from October until the end of harvest in March. The yellowing expands out from the leaf midrib into the leaf blade as the season progresses until a general yellowing of the leaves can be observed from a distance (Figure 2). Eventually, almost all leaves of the plant turn yellowish. Cold and nutrient stress appear to intensify the symptoms.

Figure 1. 

Initial symptoms of yellow leaf, with a yellowing of the lower surface of the leaf midrib of leaves 3 to 6 counting from the top expanding spindle leaf.


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Figure 2. 

More general leaf yellowing is shown on mature sugarcane plants.


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The Pathogen

Taxonomically, SCYLV is a member of the Luteoviridae family that contains barley yellow dwarf virus, soybean dwarf virus, potato leaf roll virus, and pea enation mosaic virus-1. Its classification within the family has not been fully resolved. The virus is transmitted by aphids, Melanaphis sacchari and Rhopalosiphum maidis, in a semi-persistent manner. The virus is also spread by planting infected seedcane. The virus is localized within the phloem cells of the plant and can be diagnosed by either reverse transcription-polymerase chain reaction (RT-PCR) or tissue blot immunoassays using an antibody specific for the virus (Figure 3). There is no thermal treatment effective for eliminating SCYLV in infected sugarcane.

Figure 3. 

Tissue blot serological assays results of imprinted leaf midribs of healthy (top) and infected (bottom) leaves. The light blue areas are stained phloem cells where the virus is located.


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Effect of SCYLV and its Incidence

SCYLV reduces both cane and sugar yield. In a yield trial conducted on a grower's field in Florida, hot-water-treated seedcane had 95% SCYLV incidence compared to an initial 0% incidence on commercial tissue-culture based seedcane. There was a 7% and 4% overall increase in cane and sugar yield respectively in the tissue-culture based over the heat-treated seedcane. There was no difference in sucrose content in plants between these two seedcane sources. Another yield test was conducted using seedcane derived from tissue-culture and long hot-water-treated seedcane planted in one-meter plots. The numbers of stalks, cane weight, and sucrose were significantly higher in tissue-culture seedcane plots in plant cane for all five cultivars (CP 72-1210, CP 80-1827, CP 84-1198, CP 85-1382 and CP 89-2143). In addition, the tissue-culture plots were SCYLV-free. In the first ratoon crop, the results were less dramatic and not all the differences were statistically significant. Generally yields were higher in the tissue-culture plots free of SCYLV. Cultivar CP 80-1827 was the exception, with higher yields in the heat-treated plots that were SCYLV infected. In a third experiment, seedcane was obtained from plots of tissue-culture derived seedcane that was either SCYLV-free or had become infected during the growing season. The plot weight and sucrose per plot of the SCYLV-free plots of all cultivars combined were higher than the plots with infected plants. The overall results indicate a yield loss due to SCYLV in Florida. Losses have also been reported in Louisiana and in Brazil.

In the 1990s, SCYLV was widespread in the CP cultivars grown commercially in Florida. Commercial fields planted with regular seedcane usually have at least 85% of the plants infected with SCYLV. Currently, no CP cultivar grown commercially in Florida is sufficiently resistant to remain completely free of the virus. Unfortunately, the heat therapy treatments used to control ratoon stunt do not eliminate SCYLV from sugarcane stalks. Thus, using infected seedcane transmits the virus to the emerging plants. The only way to eliminate the virus from the plant is to use meristem tissue culture techniques. Even this technique is not 100% effective and plants derived using this technique must be tested to ensure the virus was eliminated.

In Florida, a commercial seedcane company sells disease-free seedcane where SCYLV along with the ratoon stunt and other pathogens have been eliminated. Fields established with SCYLV-free seedcane will initially be virus-free. However in time, plants in these fields will become infected with SCYLV because the virus is aphid-transmitted. The average incidence of yellow leaf in fields established with disease-free seedcane and grown through one crop cycle (3 years) is 20% (average of 52 fields tested) compared to 50% (average of 106 fields) planted with regular seedcane (Bouazza Sakr, Florida Crystals Corporation, personal communication). The rate at which the plants become infected is cultivar dependent. Note this is an improvement of the 90% levels in the early 1990s. Since SCYLV-infected plants have a 4% to 10% yield loss of both cane weight and sucrose, yellow leaf is a major economic threat. Actual field losses will depend on the loss per plant and the incidence of yellow leaf in the field. Assuming a yield loss of 10% per plant and a 50% incidence level, there would be a 5.0% loss for the field in each crop. Those fields planted with tissue-culture based seedcane initially have zero or low incidence of yellow leaf, depending on the number of years since it was purchased as clean seedcane.

In summary, control of yellow leaf in the field is extremely important for Florida growers because its high incidence leads to greater economic losses to the industry than many other diseases.

Control

Until resistant cultivars can be developed, only the use of SCYLV-free seedcane can moderate SCYLV yield losses.

Footnotes

1.

This document is SS-AGR-256, one of a series of the Agronomy Department, UF/IFAS Extension. Original publication date September 2005. Revised February 2015. This publication is also a part of the Florida Sugarcane Handbook, an electronic publication of the Agronomy Department. For more information, contact the editor of the Florida Sugarcane Handbook, H. S. Sandhu (hsandhu@ufl.edu). Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

J. C. Comstock, research plant pathologist, USDA-ARS, Sugarcane Field Station, Canal Point, FL; H. S. Sandhu, assistant professor, Agronomy Department, UF/IFAS Everglades Research and Education Center, Belle Glade, FL; D. C. Odero, assistant professor, Agronomy Department, UF/IFAS Everglades REC, Belle Glade, FL; UF/IFAS Extension, 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.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.