The herbicide nicosulfuron is an important tool for weed control in maize crops; however, its incorrect use can cause yield losses to crops due to its high toxicity. The objective of this work was to evaluate the efficiency of using herbicide safener to increase selectivity of nicosulfuron to maize crops. The experiment was conducted in field conditions, and the treatments consisted of dose-response curves, using nicosulfuron at rates of 0, 15, 30, 45, and 60 g ha-1, applied with safener and/or malathion to maize crops at the V5-V6 stage. The use of organophosphorus insecticides such as malathion decrease the selectivity of nicosulfuron to maize crops. Rates of up to 60 g ha-1 were selective to the maize crops when using nicosulfuron or nicosulfuron + safener. However, plant height decreased 0.19 and 0.91 cm for each gram of nicosulfuron in the treatments nicosulfuron + safener + malathion, and nicosulfuron + malathion, respectively, at 28 days after the application. The phytotoxicity increased 0.19% and 0.97% in the treatments nicosulfuron + safener + malathion and nicosulfuron + malathion, respectively. The number of grains per row and grain yield were affected by the treatments with nicosulfuron + malathion, presenting decreases of 0.09 grains and 52 kg ha-1, respectively. Thus, adding safener to the herbicide mixture increases the selectivity of nicosulfuron to maize crops, decreases damages regarding plant height and phytotoxicity, and prevents effects of the herbicide on the number of grains per row and grain yield, up to the rate of 60 g ha-1.

This study aimed to evaluate the antagonistic effect of the mixture ofacetyl coenzyme-A carboxylase (ACCase) enzyme inhibiting herbicides and auxin herbicides in Lolium multiflorum and to determine mechanisms to mitigate this possible effect. The first experiments were conducted by associating the herbicide clethodim (108 g a.i. ha−1), quizalofop-p-ethyl (54 g a.i. ha−1), and clethodim + quizalofop-p-ethyl (108+54 g a.i. ha−1) with 2,4-D (1005 g a.e. ha−1) or triclopyr (720 g a.e. ha−1), in addition to the sole application of the respective graminicides. Another experiment included clethodim (54; 81; 108; 162; 216 g a.i. ha−1), quizalofop-p-ethyl (27; 40.5; 54; 81; 108 g a.i. ha−1), and clethodim + quizalofop-p-ethyl (54+27; 81+40.5; 108+54; 162+81; 216+108 g a.i. ha−1) mixed with 2,4-D (1005 g a.e. ha−1), or triclopyr (720 g a.e. ha−1), in addition to the control treatments without herbicide application. In the second experiment, herbicides clethodim (108 g a.i. ha−1), quizalofop-p-ethyl (54 g a.i. ha−1), and clethodim + quizalofop-p-ethyl (108+54 g a.i. ha−1) in combination with the herbicides 2,4-D (1005 g a.e. ha−1) or triclopyr (720 g a.e. ha−1)had malathion (1000 g a.i. ha−1) or glyphosate (720 g a.e. ha−1) mixed, in addition to the sole applications of the graminicides. The herbicide clethodim + quizalofop-p-ethyl did not present an antagonistic interaction with the auxin herbicides, and obtained 85% weed control. To obtain control similar to the sole application of this graminicide, the dose of the herbicide clethodim needs to be increased by 20%. However, the mixture of the herbicide quizalofop-p-ethyl with 2,4-D and triclopyr affects the ryegrass control. The use of strategies that increase the absorption of ACCase herbicides or the inhibition of P450 enzymes are ways to mitigate the antagonistic effect caused by the association of the two auxin herbicides.

No abstract

The differential growth and yield response of plant species to rising carbon dioxide concentrations and climatic change may alter species diversity within biomes. The Pampa Biome in South America is an important grassland biome of agronomic and environmental importance. Acanthostyles buniifolius (Chirca) is one of the most important weeds in natural pasture areas widely distributed in southern South America and can adversely affect livestock production. The current study was designed to identify possible responses of Chirca to CO2 concentration ([CO2]) and drought that would indicate higher adaptation and potential proliferation within the Pampa Biome. Chirca plants were cultivated at two CO2 concentrations (400 (a[CO2]) and 700 (e[CO2]) µmol mol−1) and two water conditions (under water restriction—15% of the pot capacity; and plants without water restriction—pot capacity). Besides growth parameters, we also determined water potential (ѱw), relative water contents (RWC), proline, glycine betaine, total soluble sugars, hydrogen peroxide, lipid peroxidation, superoxide dismutase (SOD), ascorbate peroxidase (APX) activity, chlorophyll A and B, carotenoids and root dry mass (RDM). Plants exposed to e[CO2] are more efficient in water use and have a greater increase in root dry mass, enabling greater adaptation to climate-induced droughts. Among the biochemical changes observed in the plants under drought stress, the accumulation of proline, glycine betaine, and total soluble sugars were the most evident mechanisms allowing plants to tolerate drought stress by osmotic adjustment.

A importância dos herbicidas residuais no controle da tiririca The role of residual herbicides in controlling nutsedge