The fruiting profile of weed-free 'McNair 235' cotton was monitored during 1984 and 1985 following overtop (OT) sprays of fluometuron (1.5 lb/A) and MSMA (1.0 lb/A). Treatments were applied to field-grown plants when 4-6 inches tall (early) or 7 days after pinhead square (late). Flower production was monitored by tagging blooms produced in 19.7 feet of row for 5 weeks in 1984 and 6 weeks in 1985. Boll set was determined by collecting retained bolls and tags at harvest.

Fluometuron sprays reduced flower production and boll set in 1984. The greatest reduction occurred when the spray was applied after pinhead square. In 1985, the early application retarded flower production and boll set for two weeks. After two weeks the early application stimulated flower production and boll set. The late application did not alter the fruiting profile in 1985.

In 1984, MSMA OT sprays stimulated boll set when applied after pinhead square without altering flower production. In contrast, these same treatments stimulated flower production without altering boll set in 1985.

Neither fluometuron or MSMA reduced yields significantly in either year of this study. The data suggests, however, that the potential yield response to these materials is dependent on environmental influences following treatment such as the length of the effective bloom period. The potential impact of these herbicides is greater when the bloom period is compressed due to late planting or unfavorable weather conditions.

Monitoring the fruiting profile response to growth regulants provides additional information to supplement conventional yield response trials. This information should assist producers and consultants make decisions regarding growth regulating materials by outlining crop development alterations resulting from the treatment.