Saflufenacil: fisiologia da atividade herbicida e efeito de sua mistura com imidazolinonas na seletividade e no controle de plantas daninhas no arroz irrigado

Abstract

In irrigated rice weeds with the greatest importance they are: weedy rice and barnyardgrass. Chemical control is currently the main method of control of these weeds. The use of cultivars tolerant to imidazolinones allows selective control. The mixture of herbicides can provide many advantages such as reduction of the amount applied and increased spectrum of action. Saflufenacil a relatively new herbicide has the potential to be applied in tank mixture with other herbicides. Moreover, it presents a recommendation for application in pre-emergence residual action in the soil. The objective of this study was to determine the effects on weedy rice control and barnyardgrass; and selectivity to rice by applying mixtures of imazapyr+imazapic with saflufenacil; evaluating the interactions between mixtures of two herbicides in weedy rice plants, as well as to assess possible changes in antioxidant metabolism during germination depending on the application saflufenacil. To achieve these goals, three experiments were conducted; The first experiment was carried out in the field, used the cultivar Puitá INTA CL, the treatments were applied alone and in mixtures of imazapyr + imazapic with saflufenacil. The second experiment was conducted in a greenhouse, where they were applied imazapyr+imazapic and saflufenacil, alone and in mixtures, each mixture was always consists of at least one sub-dose of herbicides. The results of control, reduced height and shoot dry mass of weedy rice were analyzed by Colby’s Method to check the effect of interaction. In the experiment III, soybean seeds were germinated in the presence of water or solution herbicide saflufenacil, and incubated in the dark or exposed to light (photoperiod of 14h), six days after was evaluated the changes in antioxidant metabolism and quantified the electrolyte leakage. The results of experiment I show that saflufenacil doesn’t interfere in the percentage of imazapyr + imazapic control in barnyardgrass and weedy rice, besides not causing loss of productivity in the rice crop. The lowest dose imazapic+imazapyr (36.75 + 12.25 g a.e. ha-1), alone and in mixture provided low level control of two weeds, reducing productivity. In experiment II was observed a greater number of mixtures additivity effect on the interaction between the two herbicides. Experiment III results show that there was an increase in the activity of SOD in the light and in the dark at different doses of saflufenacil, higher CAT activity at a dose of 3,0 μM in light and dark and increased APX with 3,0 μM in the light and 6,0 μM in light and dark. The H2O2 levels were higher with saflufenacil in the presence of light, MDA was raised only at the dose of 6,0 μM under light. The highest electrolyte leakage was observed in treatments with saflufenacil exposed to light. The results show that saflufenacil may be used in tank mixture with imazapyr+imazapic in irrigated rice, which can extend the weed control spectrum culture without causing productivity losses. In the absence of light saflufenacil causes increased activity of the antioxidant system, but doesn’t give damage to cell membranes.