Estrategias de manejo químico para el control de Pyrenophora teres f. teres en cebada

Net blotch (NB), caused by Pyrenophora teres f. teres (Ptt), is one of the main foliar diseases of barley, affecting both grain quality and yield. In this context, the general objective of this study was to evaluate chemical management strategies for NB control, considering the use of different seed-treatment fungicides, foliar fungicides and biostimulants products, as well as the timing of application and their interaction with cultivars exhibiting contrasting sanitary behavior against NB. To this end, two field trials were conducted during the 2024 growing season at the “Dr. Mario A. Cassinoni” Experimental Station of the Faculty of Agronomy, Paysandú department. The first trial analyzed the interaction between seed treatment and the timing of foliar fungicide mixture applications in two cultivars with contrasting responses to Ptt. In the second trial, the relationship between seed-treatment fungicides and different timings of foliar agrochemical mixtures was evaluated on a Ptt-susceptible cultivar. Epidemiological and productive variables were recorded, such as disease severity, area under the disease progress curve (AUDPC), grain yield, and thousand-kernel weight (TKW). The results showed that the evaluated chemical strategies significantly reduced disease severity, expressed as AUDPC, compared to the untreated infected control. In particular, treatments combining seed treatment with strategically timed foliar applications achieved the highest NB control efficiency. However, in several cases, the reduction in disease severity did not translate into significant differences in grain yield. Regarding TKW, significant interactions were observed between variety and fungicide treatment, indicating differential responses depending on the sanitary behaviour of the genetic material. Integrated management combining genetic resistance, seed treatment, and strategically foliar applications, proved to be an effective strategy for reducing NB severity. Nevertheless, under certain environmental conditions, a reduction in disease progress does not necessarily resulted in significant yield increases. These findings highlight the importance of considering infection timing, cultivar susceptibility, and climatic conditions when designing chemical control strategies, as well as the need for further research to better understand the relationship between epidemiological control and its impact on productivity.