|Richard Jr, Edward|
Submitted to: American Society of Sugar Cane Technologists
Publication Type: Abstract Only
Publication Acceptance Date: June 16, 1999
Publication Date: N/A
Technical Abstract: The effect on disease spread of spring mowing of cane residue from the top of sugarcane rows and lilliston cultivation of the soil above the planted line of sugarcane was tested in two commercial fields of LCP 82-89. Plants infected with Clavibacter xyli subsp. xyli (Cxx), the causal bacterium of ratoon stunting disease (RSD) were established in the center of each 58 m plot. Leaf scald caused by Xanthomonas albilineans (Xa) became naturally established throughout the experiment. A split-plot design was used in which one-half of the plots were treated in early spring with Gramoxone to simulate death of above ground shoots by frost or freeze and the other half was untreated and remained green. Subplots included the following treatments: no mowing, mowing close to the soil line, or mowing and cultivation with a lilliston cultivator. Spread of RSD and leaf scald was monitored by testing 60 stalks from each plot for Cxx and Xa infection prior to the harvest of the plant-cane and first- and second-ratoon crops. The amount of RSD spread (approx. 1%) in the plant-cane crop did not differ among the spring treatments. The incidence of RSD increased to 7% in the first-ratoon crop, but again there was no difference among spring treatments. The primary cause of the RSD spread was attributed to the mechanical harvester. Leaf scald incidence increased from .5% of plots containing infected plants in the plant-cane crop to 11.5% in the first- ratoon crop to 32% in the second-ratoon crop. The incidence of leaf scald was 18% higher in the mowed treatments than in the unmowed plots in the first-ratoon crop and 5% in the second-ratoon crop regardless of the condition of the foliage at the time of mowing.