Characterization of leaf surface, wax composition, and control of redvine and trumpetcreeper with glyphosate

Abstract

Laboratory and greenhouse studies were conducted on redvine and trumpetcreeper to characterize leaf surface and wax composition, determine responses of these weeds to glyphosate, characterize the nature of interactions between glyphosate and several selective postemergence herbicides (e.g., acifluorfen, bentazon, chlorimuron, imazaquin, and pyrithiobac) used in soybean and cotton, and determine the effects of various adjuvants on glyphosate activity on both species. Trumpetcreeper was consistently more susceptible to glyphosate than redvine. Glyphosate spray solution droplets had lower contact angle in trumpetcreeper than in redvine. Micro-roughness of the trumpetcreeper adaxial leaf surface was greater due to trichomes and glands compared to that of redvine, which had no trichomes or glands. Stomata or crystal wax deposition on the adaxial leaf surface were not observed in either species. The wax mass per unit area (22 to 37 µg cm−2) was similar regardless of the leaf age in both species. Epicuticular wax consisted of hydrocarbons, alcohols, acids, and triterpenes. Wax composition of young leaves of redvine was relatively hydrophilic (72% alcohols and acids, 24% hydrocarbons) compared to the hydrophobic components (23% alcohols and acids, 49% hydrocarbons) of old leaves. In contrast, wax of trumpetcreeper young leaves was relatively hydrophobic (9% alcohols and acids, 29% hydrocarbons), whereas old leaves had similar levels of hydrophilic and hydrophobic components (28% alcohols and acids, 31% hydrocarbons). Glyphosate mixed with selective postemergence herbicides were antagonistic when applied to redvine and trumpetcreeper, except acifluorfen. Various adjuvants did not increase glyphosate efficacy except ammonium sulfate, which increased glyphosate efficacy when applied alone to trumpetcreeper. These results showed that lower glyphosate efficacy was related to the more hydrophobic nature of redvine epicuticular waxes compared to that of trumpetcreeper.

Molecular and Biochemical Characterization of Cotton Epicuticular Wax in Defense Against Cotton Leaf Curl Disease

“…Hydrocarbons, alcohols and acids were the major compounds found in the wax of red vine (Brunnichia ovata) and trumpet creeper plants (Campsis radicans) (20). In addition to these classes of compounds, esters, phenols and other aromatic compounds were also found in this study.…”

Teores de água no solo e eficácia do herbicida glyphosate no controle de Euphorbia heterophylla

“…Embora a planta daninha em estudo apresentasse características não-favoráveis à penetração de herbicidas hidrofílicos, possivelme nt e po te nc ia li za da s pe la s co nd iç õe s climáticas desfavoráveis dentro da casa de vegetação, verificou-se que a partir da dose de 720 g ha -1 de glyphosate aos 41 DAA o controle de E. heterophylla foi superior a 85,8%, chegando a atingir 99,5% na dose de 1.080 g ha -1 (Figura 2), independentemen te do inter valo entre a última irrigação e a aplicação do herbicida. Chachalis et al (2001) Aos 7 DAA de 180 g ha -1 de glyphosate, verificou-se controle de 24,0% da planta daninha no intervalo de 0 h (Figura 3a e Tabela 4), correspondente a 26,0% de controle quando o solo apresentava teor de água de 0,23 cm 3 cm -3 (Figura 4a e Tabela 5). Com o aument o do in te rv al o pa ra 72 ho ra s, o con tr ol e de E. heterophylla decresceu para 3,5%, correspondente a 7,5% quando o solo apresentava teor de água de 0,08 cm 3 cm -3 .…”

“…A baixa eficácia de controle do glyphosate em Brunnichia ovata foi relatada ser devido à natureza hidrofóbica da cera epicuticular das folhas dessa espécie (Chachalis et al, 2001). Mendonça (2000) e Monqueiro et al (2004) observaram que Commelina benghalensis apresentou ceras epicuticulares com maior porcentagem de compostos apolares, o que pode prejudicar a absorção de herbicidas com baixo kow, como o glyphosate.…”

Action of rain on formulations of glyphosate mixed with saflufenacil for the control of Brachiaria decumbens

“…Such apparently contradictory results found in the literature indicate that, in addition to environmental conditions at the time of application, herbicide absorption efficacy may be greatly influenced by several factors such as different formulations, concentration of herbicides and surfactants, species and phenological stages of weed development, growth habits, leaf morphology and epicuticular wax composition (KIRKWOOD; MCKAY, 1994;CHACHALIS et al, 2001a;HUANGFU et al, 2007). It should be noted that a high amount of epicuticular wax may be characterized in some species as an effective barrier to the absorption of herbicides (CHACHALIS et al, 2001b).…”