Assessing the Virulence of Iranian entomopathogenic fungi isolates in control of Ephestia kuehniella (Lep: Pyralidae) (Zeller)

Entomogenous fungi include a wide range of species that are ecologically very diverse. Many of them are pathogenic to insects and mostly show host specificity. Isolation and identification of native entomogenous fungi, especially pathogenic species, and their use as a source of biological control agents is an important safe, environmentally-friendly pest control approach. This survey isolated and characterized entomogenous fungi that naturally occur in soil. Post-harvest infestations cause considerable losses in cereal production. Stored-product insect control is mainly accomplished by chemical means; however, pesticides can affect non-target species, such as plants, animals, and humans. Pesticides increase pest resistance. Another possible negative effect of pesticides is their ability to bioaccumulate and biological magnification. Therefore, alternative agents are needed for managing stored-product insect pests. Biological control of stored-product insects with entomopathogenic fungi is a successful, sustainable alternative to chemical insecticides. Mediterranean flour moth, Ephestia kuehniella, is one of the most important insect pests infesting stored grain of cereals worldwide. This study isolated and determined some entomopathogenic fungi's efficacy in flour moth biocontrol, E. kuehniella. Materials and Methods Different strains of entomopathogenic fungi were isolated from the soils of various districts of Azarbaijan province in the Northwest of Iran. Their virulence against E. kuehniella larvae was evaluated. Isolates of various entomopathogenic fungi were isolated and purified using a soil trap from twenty distinct soil specimens. The immersion technique evaluated their pathogenicity against E. kuehniella in three replicates. This was done at 104, 105, 106, 107, and 108 conidia/mL concentrations. All selected fungal isolates were identified based on morphological features and mycological parameters. Results Four isolates of B. bassiana (BVA, BVB, BVE, and BVF) and two of L. lecanii (LCA and LC) from fourteen isolates were isolated. Six fungal species, namely Lecanicillium lecanii and Beauveria bassiana, were identified among the fourteen isolates collected. The bioassay assessment revealed that E. kuehniella fourth-instar larvae were susceptible to all isolates and that the larval death rate increased with rising conidial concentration. The BVA and BVB isolates of B. bassiana showed the maximum virulence, with nearly 2.5×105 and 2.8×105 (conidia/mL) LC50, while the BVF isolate of B. bassiana had the least virulence among the other isolates evaluated, with nearly 2.2×107 (conidia/mL) LC50 on E. kuehniella. The lowest LT50 value (3.72 days) using a 108 conidia/ml concentration on E. kuehniella larvae was shown on the BVA isolate. Discussion A comparison of the means and grouping of isolates showed a significant difference between isolates and the effectiveness of different concentrations. Also, the BVA isolate of B. bassiana had greater efficiency than the other isolates, and therefore, they will be more suitable for use in plant pest biological control programs.