How long can an aryloxyphenoxypropionate herbicide be kept in the tank without losing efficacy?

Sometimes, the spray solution must be stored for some time. This study aimed to answer the following questions: how long can an aryloxyphenoxypropionate herbicide be kept in the tank without losing efficacy? Is it dependent on pH? The experiment was designed as a completely randomized design with three factors including the labeled dose of herbicides (clodinafop, cyhalofop, diclofop, fenoxaprop, fluazifop, haloxyfop, propaquizafop, and quizalofop), the pH of spray solution (5, 7, and 8), and the storage time of spray solution (0, 12, 24, 36, 48, 60, and 72 h). The efficacy of herbicides on winter wild oat Avena sterilis subsp. ludoviciana Durieu. was not affected by changing the pH of the spray solution when the spray solution was applied immediately after preparation. When the spray solutions were stored, the herbicides' highest and lowest efficacy were generally observed at pH 5 and 9, respectively. At pH 9, except for fluazifop and haloxyfop, the effectiveness of other herbicides was reduced after 12-h storage of spray solution. The efficacy of all herbicides was reduced with 24-h spray solution storage. At pH 7, the efficacy of cyhalofop and fluazifop remained stable with 72-h storage of their spray solution. In contrast, at pH 5, the efficacy of clodinafop, cyhalofop, diclofop, fluazifop, haloxyfop, and quizalofop remained stable with 72-h storage of their spray solution. Therefore, if it is necessary to keep the spray solution of aryloxyphenoxypropionate herbicides for a short time, it is recommended to use a lower pH to avoid reducing their efficacy.

How long can an aryloxyphenoxypropionate herbicide be kept in the tank without losing efficacy? Keywords:

alkaline water , chemical degradation , hydrolysis , winter wild oat