Levels of shading and application of glyphosate and carfentrazone-ethyl in the control of Macroptilium atropurpureum

Abstract

Variations in environmental conditions, such as the availability of light, can affect the efficacy of herbicides because they alter the biological characteristics of plants including those that are related to the plant’s sensitivity to herbicides. Therefore, the objective of the present study was to assess the influence of environments with different light availabilities, and of the application of glyphosate and carfentrazone-ethyl (separately or in combination) on the morphophysiology and control of Macroptilium atropurpureum. An experimental design of randomized blocks with five replicates was used, with treatments arranged in a split-plot design. The plots were composed of three levels of shading (full sunlight, 50% shading, and 70% shading); within each plot there were sub-plots, one for each of the two herbicides (glyphosate and carfentrazone-ethyl), used either separately or in combination. The doses of glyphosate + carfentrazone-ethyl applied in the treatments were 0+40 g ha-1 of carfentrazone-ethyl, 1.440+0 g ha-1 of glyphosate, 1.080+30 g ha-1 of glyphosate + carfentrazone-ethyl, and there was an additional treatment that did not include the application of an herbicide. Plants of M. atropurpureum cultivated under shading exhibited higher sensitivity to the herbicides, greater leaflet area, and lower photosynthetic rates than plants cultivated under full sunlight conditions. Under shading, both herbicides applied separately or in combination were effective in controlling M. atropurpureum, which indicates a greater susceptibility of this species to these herbicides in environments with light restriction. The species was tolerant to the two tested herbicides, used either alone or in combination, when grown under full sunlight conditions.

Luminous restriction and chemical control with glyphosate in integrated management of Urochloa brizantha L.

“…Plants with light restriction tend to have a larger area of their leaves to enhance light capture. With this, the probability of intercepting the herbicide by these plants is greater, in relation to full sun, with positive reflexes on control Costa et al, 2018). Costa et al 2018 attribute the greater sensitivity to the glyphosate of Macroptilium atropurpureum grown in the shade to the morphoanatomical characteristics favorable to the penetration and translocation of the herbicide.…”

“…The greater control observed in shading treatments can be related to plants' morphological and chemical characteristics in these environments that use their protection sources to adapt to the new environment (Costa et al, 2018).…”

“…With changes in dry mass, leaf area, amount of reserves, and amount of epicuticular wax, the herbicide's action dynamics are altered (Brant et al, 2018;Costa et al, 2018;. These factors can increase the exposure of plants to glyphosate; besides, with less reserve, they tend to decrease their ability to recover after intoxication (Silva & Silva, 2007;.…”

“…The shading provided a reduction in the reserve and epicuticular wax content, in addition to an increase in the leaf area, with which plants in these environments became more sensitive to glyphosate. The smaller amount of wax and the larger leaf area increases the plants' exposure to glyphosate, increasing its interception and absorption (Costa et al, 2018). The reduction of the amount of reserves in U. brizantha cultivated in shaded environments can increase the lack of essential amino acids caused by glyphosate, thereby increasing control efficiency.…”

Estudo De Seleção Da Comunidade Infestante Por Herbicidas Utilizando Técnicas De Análise Multivariada

“…No entanto, no presente trabalho não houve a discriminação entre glifosato isolado e combinado com carfentrazone-ethyl ou 2,4-D. Isso ocorreu devido à utilização de uma escala relativa e pelo grande diferencial entre os tratamentos no controle de A. tenella. Costa et al (2018) observaram que Macroptilium atropurpureum cultivado a pleno sol apresentou alta tolerância a dosagem do carfentrazone-ethyl e glifosato, mas a mistura dos dois herbicidas promoveu melhor taxa de controle.…”