ABSTRACT

In 2002, a field study was conducted on the Glenn Emshoff farm (Wharton County) located in the Texas Upper Gulf Coast region. This study was implemented to evaluate the application of low rates of defoliants prior to conventional practices and their impact on boll opening, defoliation, yield, and fiber quality. Four pre-conditioning treatments were applied at 650 heat units (HU) accumulated from cutout (NAWF=5) followed by a defoliation treatment at either 850, 950, or 1050 HU. Percent open bolls for the 650, 850, 950, and 1050 accumulated heat units were 10.66%, 54.85%, 70.15%, and 79.94%, respectively. Pre-conditioning treatments consisted of low rates of Prep, Dropp, Harvade, and Aim. All treatments were followed with a defoliation application that consisted of a tank-mix of Dropp and Def. Pre-conditioning treatments did not hasten boll opening or the number of days to harvest was not accelerated. Percent defoliation for 850 HU accumulated was less when compared to 950 and 1050 HU accumulated; however, defoliation was more than acceptable and did not reduce harvest efficiency or quality grades. At harvest, percent defoliation for the pre-conditioning treatments were not superior to the treatment that was not pre-conditioned (untreated check); therefore, no advantage was gained by preparing the field for defoliation and harvest. Yield was not reduced by initiating defoliation at 850 HU accumulated (55% open boll) compared to 950 HU accumulated (70% open boll) and 1050 HU accumulated (80% open boll). Three of the pre-conditioning treatments (Aim, Dropp, and Harvade) significantly reduced yields and micronaire values.