Response of cotton to prebloom square loss

In 1996 and 1997, various intensities of prebloom square removal were appli ed to three cultivars of cotton grown in Mississippi. With the exception of one cultivar in 1997, all cultivars were B. thuringiensis (Bt)-transgenic cotton. At harvest, the number of bells and seed cotton weight was recorded for all plants in each square removal treatment. All cultivars responded s imilarly to square loss. A yield increase (overcompensation) was observed i n the treatment where all squares were removed from the plant one week afte r squaring began. Only the treatment where all squares were removed before bloom significantly reduced yield and caused a large (> 7 d) delay in crop maturation. Otherwise, moderate levels of square removal (approximate to 20 -50% of prebloom squares) had little impact on overall lint production. How ever, the patterns of cotton production on the plants were significantly in fluenced by the square removal treatments. Tile removal of relatively more or larger squares increased seed cotton production in late-season fruiting cohorts and on ' vegetative ' branches. Compensation for square loss occurr ed by increasing the relative number and weight of bells produced subsequen t to early-season square removal. Typically, early-season square loss incre ased the value of later-season fruiting cohorts, especially tile midseason cohorts and bells on vegetative branches. The implications of prebloom squa re loss, including tile compensatory ability of the cotton plant, on insect management are discussed.