Home » Volume 19 / 2015 » Issue 3 »
Determining Optimum Plant Growth Regulator Application Rates in Response to Fruiting Structure and Flower Bud Removal
Chase Samples, Darrin M. Dodds, Angus L. Catchot, Bobby R. Golden, Jeffrey Gore, and Jac J. Varco
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Cotton (Gossypium hirsutum [L.]) yield is dependent on retention of first position bolls on lower sympodial branches; however, fruiting forms can abscise due to a multitude of physiological stresses or insect feeding. Fruit loss results in taller plants as energy devoted to fruit production is redirected to vegetative growth. Plant growth regulator (PGR) use has become common in cotton production systems in the U.S. PGR applications have been shown to reduce plant height; however, yield responses due to PGR application are variable. Due to insect pressure associated with the mid-southern growing region, a better understanding of PGR management is needed in the presence of fruit loss during the floral period of cotton. Field research was conducted in 2012 and 2013 at four locations in Mississippi. Flower bud and fruiting structures were hand removed at first bloom at the following rates: 0, 50 and 100%. Mepiquat pentaborate was applied immediately after flower bud or fruiting structure removal at the following application rates: 0.06, 0.11, 0.17, and 0.23 kg ai ha-1. An untreated check was included for comparison purposes. As the level of flower bud and fruiting structure removal increased, plant height, number of mainstem nodes, and nodes above the cracked boll also increased. Lint yield was similar when comparing the untreated and the 50% removal rate; with both yielding significantly greater than the 100% removal rate. Generally, as PGR application rate increased, plant height, number of mainstem nodes, and nodes above cracked boll decreased.