Resistance and Its Mechanisms of Sugarcane Varieties to Sugarcane Stem Borer Chilo infuscatellus

Abstract

Phase I. The study was conducted to compare the percent of infestation of the borers in 5 sigarcane varieties grown in Khon Kaen province in 1982. The Experiment layout was arranged in randomized complete block design with 4 replications of 5 treatments (3 breeding lines from Dept. of Agriculture : 2-1-1421, 2-1-123E, and 2-1-022E; and 2 cp,,ercoa;varoetoes : F 140 and H 48-3166). the result from the 12-month investigation showed that there were statistical significant differences differences in the infestation among 1 tp 6-month-old cane varieties. The potential resistance of each variety could be ranked by infestation percentage from low to high as following : 2-1-142L, H48-3166, 2-1-123E, 2-1022E, and F 140 respectively. However, no difference in the annual damages was found when the cane aged above 6 months. Similarity of sugar levels was suspected to be the resistant mechanism in canes at this later stage. The mechansisms of differences in the infestation among the first 6-month-old cane varieties have not been determined.
Phase II . The aim of the study was to show that sugar levels and the internode number (top or middle internodes) were the main mechanisms in the infestation determination of the borer. The tested cane was the first year ratoon of H48-3166 which was grown in the replication blocks of 10-12 m with the plant spacing of 1.20 x 0.5 m. The expertiment was arranged with 2 replicates. 2 treatments and started in Jan. 1983 as soon as the H48-3116 variety was at its fully ripening stage. The cane juice at the top internodes (internode number 4 to 6) and the middle cane internodes of the same randomed cane stem was extracted and measured by hnd refractometer for the Brix-values. A number of infested internodes were also recorded. The result confirmed that the top internodes were moe sensitive to the borer attacks than the middle internodes. Whenever, the middle internode was dameaged, its Brix level should be at least 2.1 higher than in the top internode of the same stem.