Distribution of entomopathogenic fungi inducing natural infections in Orosanga japonica (Melichar, 1898) (Hemiptera: Ricaniidae) in the Eastern Black Sea Region of Türkiye

Abstract

Orosanga japonica (Melichar, 1898) (Hemiptera: Ricaniidae) is an important pest in the Black Sea Region in Türkiye. Despite the use of various methods and microbial factors from different sources to control this pest until recently, several pathogens have been detected. Entomopathogenic fungi are important microbial agents in pest control. In the present study, we isolated eighteen fungal strains from nymphs and adults of O. japonica with fungal infection collected in Rize, Trabzon and Artvin provinces of Türkiye in 2021-2022. According to morphological and molecular characterization based on internal transcribed spacer (ITS) sequences, all strains were identified as Beauveria bassiana (Bals.-Criv.) Vuill. (Ascomycotina: Hypocreales) (OJ1-OJ18). A screening test at 1 × 107 conidia/ml revealed that all the strains caused 75–100% mortality in nymphs and adults after 7 days. Further experiments were performed with the three most effective strains, all belonging to B. bassiana (OJ3, OJ7 and OJ15). The dose‒response tests of the three fungal strains were carried out on O. japonica nymphs and adults at concentrations of 1 × 104–8 conidia/ml. As a result of the concentration-response, the B. bassiana OJ3, OJ7 and OJ15 strains presented mortality rates of 100, 98.84 and 100%, respectively, at the highest dose (109 conidia/ml) on the 10th day, and the calculated LC50 values of OJ3, OJ7 and OJ15 were determined to be 1 × 104, 1.4 × 104 and 0.3 × 103 conidia/ml against nymphs and 1.6 × 104, 1.4 × 104 and 0.4 × 103 conidia/ml against adults, respectively. The presence of B. bassiana detected natural infections and the efficacy trials conducted in the laboratory revealed that B. bassiana has potential for use against O. japonica.