Seletividade de herbicidas aplicados em pré-emergência e uso de fitorreguladores de crescimento na cultura do feijão-comum

Abstract

In the present study, an initial literature review is presented emphasizing the importance of pre-emergence herbicides for weed management in common bean (Phaseolus vulgaris L.) cultivation, as well as the limited number of active ingredients currently registered for this crop. Furthermore, the potential use of different compounds acting as growth regulators and physiological modulators in common bean production systems is discussed. Subsequently, the two scientific articles constituting the core of this thesis are presented. The first article aimed to evaluate the selectivity of pre-emergence herbicides in common bean and to quantify the yield benefits associated with their application. The experiment was conducted in Lavras, Minas Gerais, Brazil, under a randomized complete block design comprising 30 treatments and three replications, during two growing seasons (winter and summer), using the cultivar IAC Netuno. Phytotoxicity symptoms, weed control efficiency, yield components, and grain yield were assessed. Data were subjected to analysis of variance, and treatment means were grouped using the Scott–Knott test at the 5% probability level. The highest and most stable grain yields, in both winter and summer growing seasons, were obtained with the treatments containing S-metolachlor + fomesafen and flumioxazin + S-metolachlor, in addition to the weed-free control treatment. Conversely, diclosulam, sulfentrazone, and their respective combinations exhibited high phytotoxic potential to common bean plants, resulting in significant grain yield reductions. These findings demonstrate that, for the cultivar evaluation, only the mixtures S-metolachlor + fomesafen and flumioxazin + S-metolachlor exhibited satisfactory selectivity. The second article evaluated the effects of biostimulants and fungicides on the physiological management of common bean plants, associated with different application timings throughout the crop cycle. The experiments were carried out in three cultivation environments located in the municipalities of Carrancas (Environment I) and Lavras (Environments II and III), using the carioca bean cultivar IAC 2051 and the black bean cultivar IAC Netuno. The experimental design consisted of randomized complete blocks arranged in an 11 × 3 factorial scheme (ten treatments plus the untreated control combined with up to three application timings), with three replications. The total number of branches, yield components, and grain yield were evaluated. Benzyladenine and prohexadione-calcium demonstrated the greatest potential for increasing grain yield across both cultivars and cultivation environments. Benzyladenine exhibited greater responsiveness to an increased number of applications, whereas prohexadione-calcium showed greater efficiency when applied during the early developmental stages of the crop. Gibberellic acid exhibited limitations, particularly in black bean cultivars, due to excessive stimulation of vegetative growth, which negatively affected grain yield. Overall, the results demonstrate that growth regulators significantly influence yield components and grain productivity in common bean, with plant responses being dependent upon the product applied, cultivar, environmental conditions, and application frequency. Keywords: Phaseolus vulgaris; chemical control; growth modulators; common bean yield.