Effects of Various Mepiquat Chloride-Based Formulations On Cotton Growth and Yield

A study was conducted in 2009 to evaluate the effects of foliar applications of various mepiquat chloride-based formulations on cotton growth and yield. The study was conducted at the Texas AgriLife Research and Extension Center in Corpus Christi. Cotton cultivar Deltapine 141B2RF was planted on April 15, 2005 to a plant population of 50,000 in 38’ row spacing. Because of an exceptionally dry weather since early fall in 2008, irrigation was applied before planting and during the growing season. The various mepiquat chloride-based formulations evaluated were Arysta LIfeScience's commercial products, PIXPlus (MC+) and PIX/Mepichlor (MC) and the new dry Arysta formulations of MC 90WDG (90% wettable dry granule) and MC 90WDG Plus. The experimental treatments consisted of low rate, multiple applications of these formulations starting at MHS and continuing at nine (9) day intervals for a total of four (4) applications to mimic as closely as possible normal usage of these plant growth regulators. Application rates were determined by a computer program that estimates the proper rate of mepiquat for optimum vegetative to reproductive growth for the next 10 days using plant height and number of main stem nodes as primary inputs. The experimental layout included an untreated check and consisted of a randomized complete block design with six replications.  Plant growth variables, such as plant height and number of main stem nodes were measured prior to each application. A week prior to defoliation, percent open boll was measured to determine earliness differences among treatments. Plot lint yields and fiber quality were obtained by hand-harvesting 1/1000 acre. Data presented discusses the differential responses of cotton to the various mepiquat chloride formulations.