Avaliação da eficiência de bacillus spp. no controle de Ralstonia solanacearum em cultivo de fumo (Nicotiana tabacum)

Abstract

Tobacco is an important crop in Brazil, but it faces phytosanitary challenges, including bacterial wilt caused by Ralstonia solanacearum. Biological control, using microorganisms like Bacillus spp., is a promising approach to combat this disease, offering a sustainable alternative to traditional control methods. The experiment took place in field conditions in Cruz das Almas - Bahia, from May to July 2023. The choice of the study area was motivated by the previous occurrence of bacterial wilt, which resulted in reduced production. The area was subdivided into three blocks, each subjected to distinct treatments: the control, with no application (T0); with the application of 0.5L.ha-1 of a liquid inoculant composed of endospores of the bacteria B. subtilis, B. amyloliquefaciens, and B. pumilus (T1); and with double the previous application, 1.0L.ha-1 of the inoculant (T2). To assess the incidence of bacterial wilt in tobacco, a plant-by-plant diagnosis method was used, defining three grades based on symptoms: healthy plants (S), where no symptoms were observed; plants with early signs of bacterial wilt (D), which had up to two affected leaves; and plants with bacterial wilt (X), with more than two affected leaves. Productivity was calculated based on 25,000 plants per hectare, using an average of nine leaves per healthy plant and six leaves per plant with early bacterial wilt symptoms, with an average weight of 8 x 10-3 kg per leaf. Based on the results of this study, it was observed that increasing the dosage of the inoculant had a positive impact on reducing the incidence of bacterial wilt in tobacco plants. The treatment with the higher dosage (T2) had a lower percentage of affected plants (20.27%) and higher productivity (1,113 kg.ha-1) of healthy plants. On the other hand, the treatment with no application (T0) showed the highest disease incidence (45.70%) and the lowest productivity of healthy plants (378 kg.ha-1). This highlights the potential of using Bacillus spp. as an effective biocontrol agent in agriculture, resulting in healthier plants and increased productivity.