Dr. Jeff Hoy, LSU Extension Service Plant Pathologist
Sugarcane planting is once again a struggle in the industry. If there should be a window between planting and harvest (or during harvest), it would be a good time to sample old stubble fields and test for ratoon stunting disease (RSD). This disease that caused serious losses for so many years is fortunately now at low incidence in the industry, but since it has no visible external symptoms, it may be persisting undetected on some farms. The only way to make sure that an expensive healthy seedcane program is working effectively is to test for the pathogen. The LSU AgCenter Sugarcane Disease Detection Lab offers a no-charge RSD testing service.
The RSD pathogen lives in the plant xylem, and detectable populations develop in mature cane. It is most abundant in the lowest/oldest part of the stalk, so a sample for RSD testing would consist of 20-30 intact internodes (with a node on either side) collected from the base of stalks scattered across both ends of a field. The internode samples of stalks for a field should be placed in a ziploc bag (2 gal works best) then brought in for testing. It is not necessary to refrigerate the samples, but they should not be exposed to direct sunlight/heating. We need to know the variety, crop cycle year, and the healthy seedcane source (ASCL original, Sugartech, or Kleentek). If the cane has been harvested more than 3-4 times since it was obtained from a healthy seedcane source, it should be considered as field-run. To avoid having to come onto the LSU campus (currently a madhouse), samples can be delivered to the Sugar Research Station at St. Gabriel or the West Baton Rouge extension office.
RSD is usually occurring at low incidence now. With such a small sample size, it is hard to detect low levels of disease. The disease is spread mechanically by the harvester, and it builds up with multiple cuttings. This means sampling old stubble at the end of the healthy seedcane pipeline will be the best opportunity to detect RSD persisting on the farm. This is quality control testing for the healthy seedcane program. If a problem is detected, we can work with the grower to correct it. Seedcane availability has been limited for L 01-283 for some time. This means increasing seed sources on the farm, so testing to ensure this variety is healthy would be worthwhile.
If you have any questions about RSD or the testing program, please feel free to contact me: (225) 578-1392 or (225) 485-4227. Thanks for your help in controlling this important disease.