Photographer: Weerapol Ponragdee Affiliation: Department of Agriculture, Thailand Source: www.padil.gov.au Copyright:CC BY 3.0
Symptoms: The initial symptom of sugarcane white leaf disease (SCWL) is a white line that runs vertically down the middle of the leaf blades. Parallel to the initial line, white or yellow lines appear, eventually covering the entire leaf length. The change of green to white leaves is the total loss of cholorosis. Other symptoms that appear are stunted stalks and the absence of side shoots on the upper part of infected stalks, failure to set fruits and eventually kills off the plant entirely.
Host(s): Members of the genus Saccharum, the sugar genus and has been documented to infect S. edule, s. offcinarum, S. robstum, S. spontaneum (wild sugarcane). This disease is carried by leafhopper insects. There are at 12 confirmed SCWL vectors. The 2nd most prominent is the Red-Streak Leafhopper which is present in the United States and has been found on grasses nearby sugarcane fields in South Texas.
For more on Red-Streaked Leafhopper click here
With the Red Streaked Leafhopper being found near sugarcane crops in south Texas the threat of SCWL could be around the corner. Since SCWL can be identified by PCR reactions, TISI will be performing PCR reactions to determine if the leafhoppers collected are carrying SCWL. If SCWL were to be found in South Texas nearby sugarcane producing areas it would only be a matter of time before it reaches the other sugarcane producing states in the Southeast. Texas only has 3 sugar producing counties but if it were to reach Louisiana, where over half of the state is devoted to sugarcane, the results could be disastrous.
Phytoplasmas are specialized bacterium that are obligate parasites of plant phloem tissue and are transmitted by insect vectors. This phytoplasma is in the 16SrXI taxonomic group and is carried to the sugarcane crops by means of an leafhopper vector of several different species. The leafhopper has sucking mouth parts that pierce the grasses’ sheath and allows the phytoplasma to be inserted within the sugarcane crop. SCWL can remain viable in the leafhopper host for generations, being passed on from parent to offspring; also known as transovarial transmission. With SCWL staying viable within the leafhopper vector, the leafhopper acts as a reservoir for the virus and continues the life cycle.
SCWL has spread throughout Asia final sugarcane host. As with most pests and diseases, it is thought that the disease was carried along cargo ships or trucks; transporting sugarcane to towns which then spread across country boundaries.
Native Origin: Asia
U.S. Habitat: As of now the Sugarcane White Leaf Phytoplasma has not made it to the United States.
SCWL phytoplasma is difficult to control. Chemical treatment and prescribed fires, of diseased cuttings, as well as chemical control of the leafhopper vector, have proven impractical and difficult. Scientists have tried to produce phytoplasma resistant sugarcane crops but haven’t had much success. For now, the use of healthy plant material, rogueing of diseased plants and adjusting of planting time are important measures for reducing the incidence of SCWL disease.
Hanboonsong, Y., Choosai, C., Panyim, S., & Damak, S. (2002). Transovarial transmission of sugarcane white leaf phytoplasma in the insect vector Matsumuratettix hiroglyphicus (Matsumura). Insect molecular biology, 11(1), 97-103.
Hanboonsong Y, Ritthison W and Choosai C (2006) Transmission of sugarcane white leaf phytoplasma by Yamatotettix flavovittatus, a new leafhopper vector. Journal of Economic Entomology 99(5): 1531-1537.
Marcone C (2002) Phytoplasma diseases of sugarcane. Society for Sugar Production and Promotion. 4 (3&4): 79-85.
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