COTMAN a cotton-management expert system based on in-season plant monitoring was evaluated by defoliating at various levels of heat unit accumulations from date of cutout (NAWF=5.0) on yield and fiber quality. Bollman, which is one of the two components of COTMAN, was utilized to monitor the crop on a weekly basis from first flower until cutout. Once physiological cutout was determined, Bollman calculated the heat units to aid in timing of defoliation. Defoliation was initiated at five different heat unit accumulations (650, 750, 850, 950, and 1050) from date of cutout. No significant differences in yields were observed once defoliation was initiated at 750 heat units or higher. Micronaire values were reduced or lowered significantly at the 750-heat unit level. No significant differences in length or strength were observed. Results of the replicated trials suggest that COTMAN was a very effective and practical method to determine when to implement defoliation when comparing to the percent open boll or nodes above cracked boll methods.