Characterization of resistance to the Mexican rice borer (Lepidoptera: Crambidae) among Louisiana sugarcane cultivars

Cultivar resistance is a key management strategy for Eoreuma loftini in Louisiana sugarcane, but mechanisms of resistance are not well understood. This research evaluated the potential mechanisms of cultivar resistance to E. loftini among commercial sugarcane cultivars and experimental clones through a series of field screenings, greenhouse trials, and a diet incorporation assay. The stem borer resistant standard HoCP 85-845 and cultivar L 01-299 were among the cultivars with the lowest borer injury levels. Cultivars HoCP 00-950, and  L 12-201, were among the most heavily injured in field trials in both field and greenhouse trials. The variability of results from E. loftini field trials suggests that a genotype × environment effect might affect the resistance levels of cultivars. Differences in oviposition among cultivars in the greenhouse choice study were not detected, suggesting adult preference is not a key factor in resistance, and future studies should compare Louisiana’s cultivars to cultivars with known oviposition non-preference. Conversely, results from the no-choice greenhouse experiment revealed up to 3-fold differences were present among cultivars in neonate establishments. In the diet experiment, larval weight was reduced by 59.2–86.5% relative to the artificial diet control but did not differ among cultivars. These results suggest a range of resistance levels remains present in sugarcane breeding germplasm and highlight the importance of screening cultivars before commercial release. Future studies of stem borer resistance mechanisms should attempt to devise a measurement of leaf sheath tightness and pubescence.