Changes to cotton morphology and phenology associated with the frego bract and glabrous leaf genes (singly and combined) were measured in a field experiment using four near isogenic lines. Factorial analysis showed that frego bract was associated with more changes than glabrous leaf and that there were few significant interactions. Frego bract plants were 7% taller than normal bract plants at maturity, exhibited a delay in fruit production, had a greater proportion of fruit on sympodia of monopodial branches, shed more squares and had a lower proportion of reproductive to nonreproductive tissue. Glabrous-leafed plants produced fruit slightly later than hairy-leafed plants and had a lower proportion of reproductive to non-reproductive tissue. Overall, the growth of frego bract and glabrous-leafed plants was not sufficiently different from that of normal plants to warrant changes to the simple fruit model in the commercially available SIRATAC pest management program.