Behavioral and lethal effects of yeast based bioformulations on Bactrocera dorsalis

The Oriental fruit fly, Bactrocera dorsalis (Diptera: Tephritidae), is a globally significant agricultural pest necessitating novel and sustainable management strategies. This study investigated the efficacy of two stable bio-control agents derived from the naturally associated mycobiome of Zaprionus indianus: the yeast species Debaryomyces hansenii ziha1 and Pichia kudriavzevii zibd3, formulated with Essential Oil of Citral (EOC). Efficacy was evaluated via stability testing across 7 °C, 25 °C and 35 °C, compatibility assessment (T-factor), behavioral preference assays, insecticidal trials against first-instar larvae, and chemical characterization using GC-MS and Y-tube olfactometry. Both EOC-based formulations demonstrated high stability and acceptable compatibility with the fungi (EOC ≤ 1%, T ≈ 55), but exhibited strikingly opposite behavioral effects on adult B. dorsalis. D. hansenii-EOC showed significant attractant activity (- 95 ± 0.5%), which was correlated with VOCs such as Acetophenone and Hexadecenal, while P. kudriavzevii-EOC acted as a potent repellent (100 ± 0.5%), attributed to compounds including p-Mentha1,5-dien-8-ol and Naphthalene. Furthermore, P. kudriavzevii-EOC exhibited a synergistic lethal effect against pre-adult stages, causing over 50% larval mortality. In conclusion, the insect mycobiome serves as a rich and selective source for chemical ecology-based pest management, offering stable, dual-action bio-formulations (Attractant and Repellent/Larvicide) that are ideal for developing targeted "Push-Pull" or "Attract-and-Kill" strategies in B. dorsalis integrated pest management (IPM) programs.