Potential of Turkish Beauveria bassiana isolates for the management of the polyphagous planthopper, Orosanga japonica Melichar 1898 (Hemiptera: Ricaniidae)

Abstract

Background Entomopathogenic fungi are a potential biological control agent for many pests. In this study, 14 native Beauveria bassiana isolates were molecularly identified and assessed for their virulence and mortality against adults of the polyphagous planthopper Orosanga japonica, Melichar (Hemiptera: Ricaniidae) a polyphagous sap-feeding insect, under laboratory conditions. Results Isolates obtained from naturally infected adults O. japonica were molecularly identified as B. bassiana by sequencing the internal transcribed spacer and 26S large subunit of ribosomal DNA. In the bioassay, the radial growth and sporulation of isolates significantly differed (P < 0.05). Concentration-time bioassays demonstrated that all isolates had a lethal effect on adult O. japonica at the concentration of 1 x 10(8) conidia ml(-1). The lethal times LT50 and LT90 values for each B. bassiana isolate, which indicate the time required to kill O. japonica, ranged between 2.44-3.19 and 3.78-5.01 days, respectively, at 20 degrees C, while their values were 1.74-2.76 and 2.76-4.10 days, respectively, at 25 degrees C depending on the native isolates. The concentration-mortality response showed a statistically significant difference between some isolates B. bassiana tested against adult O. japonica individuals (P < 0.05). With an LC50 value of 2.29 x 10(6) conidia ml(-1), the lowest effective EPF isolate for O. japonica was KA-78-14. The isolates caused 100% adult mortality in O. japonica within five days, while the mortality in the control group was less than 10%. Conclusions These findings suggest that some B. bassiana isolates were more virulent on O. japonica and may play an important role in the biocontrol of O. japonica in Turkey.