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Title: Effects of Harvester Type, Inoculum Source, and Cultivar on Spread of Ratoon Stunting Disease

item Grisham, Michael

Submitted to: Sugar Cane International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2006
Publication Date: 5/20/2006
Citation: Grisham, M.P., Hoy, J. 2006. Effects of Harvester Type, Inoculum Source, and Cultivar on Spread of Ratoon Stunting Disease. Sugar Cane International. 24(3):3-6.

Interpretive Summary: Ratoon stunting disease (RSD) of sugarcane is spread mechanically from plant to plant during the harvesting operation and since stalks are harvested from sugarcane plants annually for 3 to 5 years, disease incidence can increase with each harvest. For over five decades, the primary sugarcane harvester in Louisiana was the whole-stalk harvester; however, since 1995 there has been an increase in the use by growers of the chopper harvester that cuts the stalk into 6- to 9-inch pieces. Side-by-side experimental plots with approximately 1 meter of diseased plants at the beginning of each plot were harvested with either the whole-stalk or chopper harvester. RSD spread occurred with both harvesting systems; however, spread was greater in some years following harvest with the whole stalk harvester compared to harvest with a chopper harvester. It was also found that the greater the number of RSD-causing bacteria found in a variety of sugarcane, the greater the spread of the disease. Even without highly resistant varieties, the wide-spread planting of varieties that support lower populations of the disease-causing bacterium can reduce the incidence and, therefore, the effects of RSD. The shift in harvesting systems does not appear to have increased the risk of greater RSD spread.

Technical Abstract: The effects of harvester type, inoculum source, and cultivar on the spread of ratoon stunting disease (RSD) were determined in field experiments conducted in Louisiana. RSD spread was greater in some crop cycle years following harvest with a whole stalk harvester compared to a billet harvester. The cultivar used as inoculum source had no effect on extent of RSD spread. Cultivars varied in the extent of RSD spread. The number of stalk vascular bundles colonized by bacteria was positively correlated with the extent of RSD spread in seven cultivars.