Biological Control of Bradysia odoriphaga Using Coenosia attenuata with Banker Media System and Mulch Layer

Greenhouse cage trials were conducted to evaluate the biocontrol potential of the predatory tiger fly Coenosia attenuata against the Chinese chive maggot Bradysia odoriphaga infesting Allium tuberosum. To ensure that adult C. attenuata have sufficient food when the B. odoriphaga adults decline or are absent, we supplemented the predator with alternative prey (Drosophila melanogaster adults), a banana-based banker medium, and a coir mulch layer across four treatments with three replicates per treatment over 50 weeks. When C. attenuata was released alone (T1), corrected control efficacy against B. odoriphaga larvae ranged from 56.14% to 59.82%. Notably, peak larval suppression was significantly higher in treatments combining the predator with a mulch layer (T2: 94.23%) or with the banker media system (T4: 100%). Against adult stages, T1 achieved 32.68–69.73% corrected efficacy, whereas T2 and T4 reached peak values of 100% and 97.69%, respectively. Predator application also doubled the total cumulative dry weight of Chinese chive. However, the concurrent use of banker medium and mulch layer (T3) did not produce synergistic effects. Collectively, these findings demonstrate that banker media systems and coir mulch layers are effective auxiliary tools for enhancing C. attenuata-based biocontrol in protected cultivation systems.