Hormesis of 2,4-D choline salt in productive aspects of cotton

Investigating the impacts of airborne dust on herbicide performance on Amaranthus retroflexus

Dust pollution poses environmental hazards, affecting agriculture through reduced sunlight exposure, photosynthesis, crop yields, and food security. This study explores the interference of dust pollution on herbicide efficacy to control weeds in a semi-arid region. In a factorial experiment conducted in 2019 and replicated in 2020, the interaction of dust and various herbicide applications, including bentazon, sulfosulfuron, tribenuron-methyl, aminopyralid + florasulam, foramsulfuron + iodosulfuron + thiencarbazone, 2,4-D + MCPA, and acetochlor, in controlling Amaranthus retroflexus L. were assessed. Dust induced a 9.2% reduction in the total chlorophyll content of A. retroflexus, while herbicide application independently led to a 67.5% decrease. Contrary to expectations, herbicides performed better in dust, except bentazon, which caused a 28% drop in plant height and a 29% decrease in total biomass compared to non-dust conditions. Both herbicides and dust exerted suppressive effects on A. retroflexus's leaf and stem weights and overall biomass. Despite dust presence, tribenuron-methyl (95.8%), aminopyralid + florasulam (95.7%), sulfosulfuron (96.5%), and foramsulfuron + iodosulfuron + thiencarbazone (97.8%) effectively controlled A. retroflexus. These findings indicate that dust's effect on herbicide efficacy is herbicide-dependent but except bentazon, dust generally increased herbicide efficacy and amplified the control of A. retroflexus.

Effect of glyphosate in Johnsongrass submitted to different soil water potentials

This work aimed to study the efficiency of herbicide glyphosate to control Johnsongrass plants (Sorghum halepense) in different phenological stages of development and when submitted to different types of soil water potentials. The study was conducted in a completely randomized design, with four repetitions. The treatments were arranged in a triple factor scheme 3 × 3 × 2, being: three soil water conditions [no water deficit (-0.03 MPa), intermediate water deficit (-0.07 MPa), and high water deficit (-1.5 MPa)], associated with three doses of glyphosate (0.0, 270.0, and 540.0 g a.e. ha^-1) applied in two phenological stages (4-6 leaves and 1-3 tillers). Visual control evaluations were conducted at 7, 14, 21, and 35 days after the herbicide application. Biometric and morphophysiological parameters were also analyzed. With the increase of water restriction, there was a decrease in Johnsongrass morphophysiological components, such as specific leaf area, stomatal conductance, and the difference between environment and leaf temperature, as well as the accumulation of aerial part and roots dry matter, independently of the phenological stage evaluated. The development stage of Johnsongrass influenced the control provided by glyphosate, independently of the dose used. The different water deficits studied reduced the control of glyphosate in the two Johnsongrass development stages evaluated. Severe water deficits reduced the control of glyphosate in Johnsongrass using the recommended dose. In conditions of moderate water deficit, the control was not affected. Thus, the control with lower doses can be the most affected by water deficit.

Effect of different soil water managements on the selectivity of fomesafen in conventional and RR soybean

The study aimed to study the selectivity of the herbicide fomesafen, sprayed at different growth stages of the conventional and RR soybean cultivars, under different soil water managements. Two soybean cultivars were used: MG/BR 46 Conquista (conventional) and BRS Valiosa (RR), submitted to the spraying of fomesafen at two phenological stages (V2-first open trefoil; V4-third open trefoil), under three soil water conditions (-0.03, -0.07, and -0.5 MPa). Under water scarcity conditions, soybean plants have lower visual phytotoxicity when subjected to the spraying of the herbicide fomesafen. There were anatomical differences between the leaf blades of the conventional (MG/BR 46 Conquista) and transgenic (BRS Valiosa - RR) cultivars, and the water scarcity changed the anatomy of the soybean plants. The condition of moderate water shortage (-0.07 MPa) led the conventional cultivar to present a lower development than the transgenic cultivar. The transgenic cultivar had a greater ability to sustain the biological nitrogen fixation under moderate water shortage conditions (-0.07 MPa) than the conventional cultivar.

Can 2,4-D promote the hormesis effect in upland rice?

This study aimed to evaluate the influence of low doses of 2,4-D on the agronomic traits of upland rice applied at different stages of crop growth. The work was carried out in a randomized completly blocks, and consisted of the application of 5 low doses of the 2,4-D herbicide (0, 0.68, 1.36, 2.04, 3.40 and 5.44 g acid equivalent (e.a.) ha-1) in two stages of rice development (tillering and floral differentiation). Nitrogen contentes in leaves, SPAD index and yield are higher when low doses of 2,4-D is applied in the tillering stage. Application of 2,4-D at a dose of 2.04 g a.e ha-1 results in a 19% increase in the number of spikelet per panicle. On the other hand, there is no effect of the application of low doses of 2,4-D on height, number of stems, active tillering and weight of 100 seeds. Our results contribute to increase knowledge of the hormesis effect in plants in order to increase crop yield.