Controle de Senecio madagascariensis e de Senecio brasiliensis pelo pastejo com ovinos

Abstract

This thesis reports two outbreaks of S. madagascariensis poir poisoning diagnosed in cattle in October 2013 in southern Rio Grande do Sul were also reported. Morbidity rate were 3.2% and 6.1%, and lethality rate was 100%. A third poisoning case occurred on a property in which one animal died out of 54 cattle with clinical signs of intoxication. In all cases observed here, the cattle were in areas highly infested by blooming S. madagascariensis. The observation of large numbers of S. madagascariensis in several farms in the municipalities of Arroio Grande, Pedro Osório and Capão do Leão reinforces that this plant is in the process of adaptation and dissemination in this region and that other outbreaks may occur in coming years. The plant invades pastures, natural pasture and crops causing losses in agriculture. This thesis also presents the results of three experiments performed to test different methods of controlling Senecio madagascariensis poisoning. Forty sheep were placed in a four-hectare area, with medium/high levels of infestation by the plant, in continuous grazing for 90 days. The second experiment was conducted with 10 sheep grazing for 30 days and 60 days’ rest in three areas of 0.5 hectares each. The areas had low, medium and high levels of infestation of S. madagascariensis. For the control of S. brasiliensis and other species of the plant, another experimet was carried out on a farm with history intoxication by Senecio spp. in cattle. Eighty-six sheep were used in an area of 90 hectares for a year. The results of these experiments demonstrated that sheep consume and decrease the amount of S. madagascariensis in infested areas. Furthermore, it also showed that S. madagascariensis to be controlled efficiently requires continuous grazing sheep. Practices as drying the pastures with herbicides, tillage and pasture planting can help eliminate the plant in long-term plan. In areas with S. brasiliensis infestation mowing can be an effective practice, especially in areas where the plant is too high for an easy consumption by sheep.