Selectivity of Iodosulfuron-Methyl Association with ACCase Inhibitors and 2.4-D in Wheat and Barley Crops

Abstract

This research aimed to assess the selectivity of treatments involving the commercial formulations tank mixtures of iodosulfuron-methyl with herbicides ACCase inhibitors (fenoxaprop-p-ethyl and clethodim) and synthetic auxins (2.4-D), applied in post-emergence of wheat (Triticum aestivum) and barley (Hordeum vulgare) crops. Three experiments were conducted in the field, during the 2014 crop year. A randomized complete block design was used with 11 treatments and five replications. Treatments consisted of (g ha-1): 1) iodosulfuron-methyl (6.5), 2) fenoxaprop-p-ethyl (82.5), 3) fenoxaprop-p-ethyl + clethodim (55 + 54); 4) 2.4-D (335), 5, 6 e 7) iodosulfuron-methyl + fenoxaprop-p-ethyl (6.5 + 82.5; 6.5 + 110 and 6.5 + 165), 8) iodosulfuron-methyl + fenoxaprop + clethodim (6.5 + 55 + 54), 9) iodosulfuron + fenoxaprop-p-ethyl + 2.4-D (6.5 + 110 + 335), 10) iodosulfuron-methyl + fenoxaprop-p-ethyl + clethodim + 2.4-D (6.5 + 82.5 + 72 + 335) and 11) check without weeds. Associations of iodosulfuron-methyl + fenoxaprop-p-ethyl (6.5 + 82.5; 6.5 + 110 and 6.5 + 165 g ha-1) associations, as well as of iodosulfuron-methyl + fenoxaprop-p-ethyl + 2.4-D (6.5 + 110 + 335 g ha-1) were selective for BRS Campeiro and BRS Gralha azul wheat cultivars and did not feature symptoms of intoxication and significant losses in grain yield and hectoliter weight, when compared to the treatment with no application. For BRS Brau barley cultivar, only iodosulfuron-methyl + fenoxaprop-p-ethyl associations, in doses of 6.5 + 82.5 and 6.5 + 110 g ha-1 were feasible for selectivity. Clethodim addition in iodosulfuron-methyl + fenoxaprop-p-ethyl or iodosulfuron-methyl + fenoxaprop-p-ethyl + 2.4-D associations caused negative effects for wheat and barley crops. Commercial formulation of iodosulfuron-methyl (Hussar™) resulted in protection for damage effects of fenoxaprop-p-ethyl (Podium EW™) for studied crops.

Selectivity of 2,4-D salts to barley plants applied at distinct phenological crop stages

“…When comparing the application between crop development stages for each treatment, it was found that the tillering stage and after the first node for 2,4-D amine and the first node stage for 2,4-D choline demonstrate the highest barley grain yields. The 2,4-D amine was reported to not affect grain yields of wheat (Piasecki et al, 2017) and barley (Karpinski et al, 2018), which corroborates in parts with what was observed in this work.…”

“…In the other treatments and stages of barley plant development, there were no changes in the hectoliter weight of the grains. Karpinski et al (2018) observed that 2,4-D amine application did not cause a reduction in hectoliter weight of the barley cultivar BRS Brau.…”

“…When not properly controlled, weeds can cause high losses to producers by competing with the crop for water, light, and nutrients. In addition, weeds can host insects and diseases, and also release allelopathic substances that interfere with barley growth, development, and consequently grain yield and quality (Tironi et al, 2014;Karpinski et al, 2018;.…”