Screening of some South African maize (Zea maysL.) cultivars for acetochlor tolerance

Abstract

Acetochlor containing a safener is registered for pre-emergence use on maize to control mainly annual grasses. It is applied at rates of between 0.49 and 1.89 kg ai ha -1 on soils with a clay content from <10% to 55%. Some cases of acetochlor injury to maize have occurred in the field despite the correct application rates being used. A randomised complete block design trial was conducted in a glasshouse set at 28/18°C day/night to screen 21 maize cultivars for their tolerance to acetochlor (WENNER 700 S EC ® ). Maize was planted in pots containing a sandy loam soil (15% clay). Five acetochlor rates (0, 0.74, 1.47, 2.94 and 5.88 kg ai ha -1 ) were applied the next day and leached into the soil. Characteristic symptoms of acetochlor phytotoxicity occurred, particularly at higher application rates. Most cultivars showed significant decreases in both plant height and dry mass at the recommended application rate. Significant differences were noted between cultivars, with slight variations in results for seedling height and dry mass. Cultivars were grouped into tolerant, intermediate and sensitive classes based on their reaction to the herbicide. Most cultivars were rated as intermediate, although both tolerant and sensitive cultivars were found, so proving the existence of cultivar differences with respect to acetochlor tolerance.

Environmental Fate and Effects of Dichloroacetamide Herbicide Safeners: “Inert” yet Biologically Active Agrochemical Ingredients

“…6,39 Dichloroacetamide safeners are typically applied as preemergence spray formulations that also contain a chloroacetamide herbicide (Table 2). 20,30 Benoxacor, for example, is commonly paired with S-metolachlor in commercial formulations such as Dual II Magnum (Syngenta).…”

“…Dichloroacetamide safeners have been in commercial use for more than four decades and are currently used on several continents, including North America, Europe, Africa, and Asia. , Dichloroacetamide safeners are typically applied as pre-emergence spray formulations that also contain a chloroacetamide herbicide (Table ). , Benoxacor, for example, is commonly paired with S -metolachlor in commercial formulations such as Dual II Magnum (Syngenta). , Dichlormid is often paired with acetochlor (e.g., Surpass EC, Dow AgroSciences) and can also be combined with thiocarbamate herbicides. ,, Furilazole is commonly paired with acetochlor (e.g., Degree, Monsanto). − , AD-67 is frequently sold separately from its common herbicidal partner (acetochlor); formulations containing AD-67 are typically prepared by users.…”

“…Dichloroacetamide safeners have been in commercial use for more than four decades 38 and are currently used on several continents, including North America, Europe, Africa, and Asia. 6,39 Dichloroacetamide safeners are typically applied as preemergence spray formulations that also contain a chloroacetamide herbicide (Table 2). 20,30 Benoxacor, for example, is commonly paired with S-metolachlor in commercial formulations such as Dual II Magnum (Syngenta).…”