Abstract
Powdery mildew, caused by Blumeria graminis f.sp. hordei, represents one of the most significant biotic threats to barley (Hordeum vulgare L.) cultivation in arid and semi-arid regions. This study evaluated the effectiveness of selected four chemicals inducers (salicylic acid, oxalic acid, tannic acid, and benzothiazole) and two fungicides (mancozeb and thiophanate-methyl [Topsin-M70%]) in reducing disease severity and improving yieldrelated traits in two barley cultivars (‘Areg’ and ‘Wady Bargoge’) under Libyan field conditions. The experiments were laid out in a randomized complete block design (RCBD) with three replications. Foliar treatments were applied at the heading stage and ten days later. Data were collected on disease incidence, disease severity, and key agronomic traits, including grain yield, 1000-grain weight, and harvest index. The results revealed that Benzothiazole was the most effective treatment, significantly reducing disease severity and incidence while enhancing grain yield, grain weight per spike, and biological yield. The Areg cultivar responded more favourably than Wady Bargoge, indicating varietal differences in resistance and productivity under induced systemic resistance. In contrast, Topsin-M70% exhibited the lowest performance in both disease control and yield improvement. The study underscores the potential of chemical resistance inducers, particularly Benzothiazole, as sustainable alternatives to conventional fungicides. These findings support the integration of such inducers into eco-friendly disease management strategies and highlight the need for further optimisation and combination with biological agents to enhance barley resilience in low-input production systems. Keywords: Hordeum vulgare, powdery mildew, benzothiazole, induced resistance, fungicides, disease severity, Libya.