Avaliação da infectividade de propágulos do isolado fúngico p081 em plântulas de capim-amargoso (Digitaria insularis)

Abstract

Sourgrass (Digitaria insularis) stands out as one of the main weeds affecting Brazilian crops, characterized by its high capacity for dispersal, germination, and resistance to herbicides, especially glyphosate. This resistance has hindered the chemical management currently used, increasing production costs and significantly reducing crop productivity. Therefore, the fungal isolate P081 demonstrates great potential for controlling this weed. This isolate survives and spreads in the environment through the production of infective propagules, such as conidia and chlamydospores, which have the ability to inhibit seed germination and the growth of sourgrass seedlings. In this context, the objective of this study was to evaluate the efficiency of the propagules produced by isolate P081 on D. insularis seedlings to determine its potential as a biological control agent for future use in bioherbicide formulations. The experiment was conducted in a completely randomized design with five treatments and five replications, evaluating different combinations of conidia, chlamydospores, and the adjuvant Ranchero®. The plant population was evaluated using the rating scale proposed by the Brazilian Weed Science Society (SBCPD, 1995), and the symptoms in inoculated plants were observed at 3, 5, 7, 10, and 12 days after application (DAA). Data were submitted to analysis of variance (ANOVA) and Tukey’s test at a 5% probability level. Isolate P081 produced average concentrations of 2.15 × 10⁶ conidia mL⁻¹ and 3.36 × 10⁶ chlamydospores mL⁻¹. Among the treatments, the application of chlamydospores associated with Ranchero® showed the best performance, reaching 94.8% control at 12 DAA, with symptom progression characterized by chlorosis, necrosis, and seedling death, demonstrating the high potential of chlamydospores for bioherbicide development. Thus, this research contributes to innovative integrated weed management strategies, providing sustainable alternatives and reducing dependence on chemical herbicides.