Eficácia e seletividade de associações de herbicidas inibidores da PPO e do fotossistema II aplicados em pós-transplante de mudas pré-brotadas de cana-de-açúcar

Abstract

Efficacy and selectivity of associations of PPO and photosystem II inhibitor herbicides applied in post-transplant of pre-sprouted sugarcane seedlingsWeeds compete directly and indirectly with the sugarcane crop, harming production. In this way, controlling these weeds is of great importance to achieve high productivity. The chemical management of weeds is one of the most efficient methods, however, depending on how the herbicides are applied, they can cause damage to the crop. Therefore, knowing the phytotoxic effect that the application of herbicides can cause in pre-sprouted seedlings is necessary. Thus, the objective of this work was to evaluate the effectiveness and selectivity of associations of protox and photosynthema II inhibitor herbicides in post-transplant of pre-sprouted sugarcane seedlings, when compared with other associations of herbicides practiced by sugarcane producers. Two projects were carried out, the first one in a greenhouse, following a completely randomized design, with four replications and a 10 x 2 factorial scheme, where the first factor corresponded to the treatments (control; (sulfentrazone + diuron) (525.0 + 1050.0); (sulfentrazone + diuron) (700.0 + 1400.0); (sulfentrazone + diuron) (875.0 + 1750.0); (sulfentrazone + diuron) + mesotrione (700.0 + 1400.0 + 120.0); diclosulan + tebuthiuron + ametryn (70.6 + 750.0 + 1500.0); diclosulan + s-metolachlor + ametryn (70.6 + 2400.0 + 1500.0); 2.4-D (1005.0) for dicots and metribuzin (1920.0) for monocots; MSMA + ametryn (1185.0 + 1500.0) and flumioxazin + tebuthiuron (125.0 + 750.0), doses in g a.i. ha -1 ) and the second at two application times (post-initial (2 to 4 leaves/1 to 2 tillers) and late post (6 to 8 leaves/3 to 4 tillers)). This scheme was carried out in 11 independent experiments, one for each weed studied (Luffa aegyptiaca; Ipomoea hederifolia; Merremia aegyptia; Ricinus communis; Momordica charantia; Mucuna aterrima; Digitaria nuda; Rottboellia exaltata; Brachiaria plantaginea; Brachiaria decumbens and Panicum maximum) . The sampling units were composed of 3.0 L pots filled with sandy-clay soil and the weeds were sown according to the company's recommendation. After sowing the weeds, the pots were kept in a greenhouse with irrigation. When the weeds reached the necessary phenological stages, application was carried out with a costal sprayer pressurized with CO2. Control assessments were performed at 7; 14; 21; 28; 35 and 42 days after application (DAA), following the visual rating scale proposed by ALAM (1974). At 42 DAA, shoot dry mass was evaluated, cutting the remaining plants close to the ground, placing them in paper bags and taking them to an air circulation oven until they reached constant weight. The data obtained were analyzed by the F Test at 5.0% and, when significant, by the Scott-Knott Test also at 5.0%. The second project was conducted in the field, in two seasons (2018/2019 and 2019/2020), following a randomized block design, with 4 replications and 14 treatments (control without weeding; control weeded; (sul...