pH and water hardness on the efficiency of auxin mimics herbicides

Abstract

Carrier water quality is one of the main characteristics for an efficient and safe spraying of pesticides. Overall related to the levels of pH and hardness. The objective was to evaluate the interaction between water pH and storage time of the spray, containing 2,4-D amine, 2,4-D choline and dicamba, on the visible efficacy in Ipomoea triloba, Bidens pilosa, Amaranthus viridis; and water hardness on I. triloba. Three studies were carried out in a greenhouse. Study 1 with a 3x5 factorial, which factor A being pH of 2, 6 and 10 and factor B being 0, 2, 6, 24 and 36 hours of application after the mixture. Study 2 was a 3x5 factorial for each herbicide, whith factor A being the levels of pH (2, 6 and 10) and factor B being 0, 6, 12, 24 and 48 hours of application after the mixture. The study 3 is a 3x7 factorial, with factor A being the herbicides and factor B levels of water hardness: 0, 65, 125, 250, 500, 750 and 1000 parts per million. The pH of all solutions remained stable for 48 hours after preparation. However, did not interfere in efficacy of dicamba in I. triloba. Also, longer time between preparing the spray with 2,4-D formulations and application caused reduction efficacy on I. triloba. Also, the level of water hardness decreased control on I. triloba. The pH of carrier water did not affect efficacy of 2,4-D and dicamba on the weeds; however, longer time of the spray application reduce the visible efficacy.