During the fall of 2002 and 2003, sugarcane borer, Diatraea saccharalis (F.), population samples from various sugarcane production locations in Louisiana showed up to 2.7-fold (LC50) and 3.9-fold (LC90) decreases in susceptibility of 1st instar larvae on a tebufenozide (ConfirmŽ), an ecdysone agonist, incorporated diet. Insecticide resistance monitoring initiated due to substantially increasing use of tebufenozide (approaching two long residual applications per field, annually) has shown the value of establishing pre-exposure population susceptibility in a bioassay methodology. Despite discontinuance of use for one year, reversion to an earlier level of susceptibility was not observed. Because of a significant lack-of-fit with the probit model for data from some of the more resistant colonies, a discriminating dosage was also used. Lighter weight pupae in the Calcasieu-Jefferson Davis strain suggest that tebufenozide resistance mechanisms may have a biological cost in terms of ecological fitness, especially at early stages of resistance development. Resistance monitoring and alternation of management chemistry is expected to help preserve this valuable sugarcane IPM tactic. Together with a carefully orchestrated balance among control tactics, pest selection pressure can be minimized to create a greater permanency in the sugarcane pest management program.