Cotton harvest aid regimes and their interaction with cotton cultivar characteristics impacting leaf grade

Cotton (Gossypium hirsutum L.) leaf grade values significantly increase with remnants of leaf and bract materials in cotton lint and can result in economic discounts to the producers. We are hypothesizing that cotton harvest aid regimes, and level of defoliation and desiccation are contributing factors in higher cotton leaf grades. The interaction of morphological characteristics of cotton cultivars and the various harvest aid regimes were evaluated to identify key factors contributing to the increased leaf grade values. Multiple trials were conducted during 2010, 2011, and 2012 in Burleson, Colorado, and Matagorda counties in South and southeastern Texas. Cotton cultivars were selected with a range of leaf hairiness and were sprayed with five harvest aid treatments to obtain a range of defoliation and desiccation levels. Leaf and bract pubescence, and leaf and bract area were collected, as well as defoliation and desiccation levels, to analyze the resulting impact on cotton leaf grade values. Seed cotton samples were ginned in a microgin and lint quality was measured with high volume instrument (HIV) analysis. Results from trichome density quantification indicated substantial variation in cultivars and discrepancies from company based rating systems. Defoliation level rating ranged from 0 to 84% at 14 d after treatment application, while desiccation levels were low despite the use of herbicidal products. Defoliation or desiccation did not impact leaf grade. Leaf grades generally increased with higher leaf trichome densities, although not always significantly. Among morphological characteristics of cotton, leaf hairiness is more important for cultivar selection to reduce leaf grade.