Beauveria bassiana Bals. as a biological agent for reducing Spodoptera exigua Hub. attacks on Allium fistulosum L.

Welsh onion (Allium fistulosum L.) is a vegetable crop with high economic potential in the agricultural sector. One of the major pests affecting Welsh onion cultivation is Spodoptera exigua Hub. An environmentally friendly approach for controlling this pest is the use of the entomopathogenic fungus Beauveria bassiana Bals. This study aimed to evaluate the effectiveness and optimal concentration of B. bassiana in reducing the infestation intensity and increasing the mortality of S. exigua on Welsh onion plants. The experiment was conducted using a Randomized Block Design (RBD) consisting of six treatments and four replications, resulting in 24 experimental plots. The treatments included: P0 (control, without B. bassiana application), P1 (B. bassiana 10 g L−1 water), P2 (B. bassiana 20 g L−1 water), P3 (B. bassiana 30 g L−1 water), P4 (B. bassiana 40 g L−1 water), and P5 (B. bassiana 50 g L−1 water). The results demonstrated that the application of B. bassiana effectively suppressed the infestation intensity of S. exigua by up to 87.98% and increased pest mortality by 80.67% on Welsh onion plants.