Potential of entomopathogenic fungi as biological control agents of Yponomeuta malinellus Zeller, 1838 (Lepidoptera: Yponomeutidae)

The apple ermine moth, Yponomeuta malinellus Zeller, 1838 (Lepidoptera Yponomeutidae), is a common pest of apple trees in Asia and Europe, and it has spread to North America. In apple growing regions of Turkey, the population of this pest may increase from time to time, requiring a separate control measure. In such cases, Turkish apple growers generally rely on synthetic insecticides to control this pest. The present study aimed to evaluate indigenous isolates of some entomopathogenic fungi (EPFs) against the pest as potential biological control agents. In the pathogenicity tests, 14 EPF isolates that belong to 4 fungal species [Beauveria bassiana (Bals.) Vuill. – 7, Clonostachys rosea (Link) Schroers – 3, Isaria farinosa (Holmsk.) Fr. – 2 and Purpureocillium lilacinum (formerly known as Paecilomyces lilacinus (Thom) Samson) (Thom) Luangsa-ard, Houbraken, Hywel-Jones & Samson – 2] were assayed against the 4th instar larvae of Y. malinellus under laboratory conditions. All the EPF isolates were tested against the pest with three different conidial suspensions (1 × 107, 1 × 108 and 1 × 109 conidia ml-1), using the spray method. The results of pathogenicity assays demonstrated that the effectiveness of the isolates increased with increasing concentration and elapsed time up to 9 days after treatment. Of the 14 isolates tested, 3 B. bassiana isolates (BbDm-1, BbDs-2 and BbKm-3) were the most pathogenic, causing mortalities between 96.7% and 100% at the highest concentration 9 days post treatment. All the results suggest that the most pathogenic above-mentioned 3 isolates of B. bassiana have a significant biocontrol potential against Y. malinellus.