Plant mapping experiments were conducted for two years (1986 and 1987) on the Plant Science Research Farm at Mississippi State, MS, to determine where and when bolls were made. Four cotton cultivars, "Stoneville 213," "DES 119," "Deltapine 50" and "McNair 235" were planted in a 2 to 1 skip row pattern, replicated 6 times. Plots were thinned to 4 plants per foot. Insects were controlled by spraying once a week with azinphosmethyl and fenvalerate. A 10-foot strip was marked in each plot to use for mapping. During the month of July blooms were tagged each day on plants in the 10-foot strip. In October, after all bolls had opened, the plots were harvested by hand. Bolls from each position on the plants in the 10-foot strip were kept separate, counted and weighed.

When comparisons were made on cumulative percent of total yield by branch 12, ST-213 had 42% of its total yield while DES-119 had 48%. After branch 12, ST-213 out performed DES-119. However, DES-119 out yielded ST-213 by more than 500 lbs (seed cotton) per acre during the two-year study.

When comparisons were made between McNair 235 and DPL-50, results showed both yielded the same, however, McNair 235 had significantly fewer but larger bolls than DPL-50.

These studies indicate that early maturing cultivars set fruit earlier than a full season cotton. Also, boll number and size differ among varieties.

One can conclude that entomologists can no longer make general recommendations in the control of cotton pests but must be aware of the variety of cotton the grower has planted.