Natural infestation of entomopathogenic fungus Beauveria pseudobassiana on overwintering Corythucha arcuata (Say) (Hemiptera: Tingidae) and its efficacy under laboratory conditions

The invasive oak lace bug Corythucha arcuata (Say, 1832) (Hemiptera: Tingidae) was first recorded in lowland stands of pedunculate oak (Quercus robur L.) in Eastern Croatia in 2013, from where it expanded to the west causing summer yellowing and intensive chlorotic damages of oak leaves. In 2018, the entomopathogenic fungus Beauveria pseudobassiana Rehner and Humber (Hypocreales: Cordycipitaceae) was isolated from several dead C. arcuata adults found in moss, a typical place for overwintering. The first aim of this study was to estimate the number of overwintering adults per m2 of moss, their natural mortality, and natural infestation by this fungus. Moss and oak lace bugs were collected from oak trees at six different locations in infested forests in Spac?va basin. C. arcuata individuals were counted and separated for further analysis and determination of possible fungal infections. Results demonstrated a high rate of mortality among overwintering individuals (65%), with 19% of them infested by various entomopathogenic fungi, of which 70% belonged to B. pseudobassiana. The second aim of this study was to test fungal virulence against C. arcuata under laboratory conditions and to study differences between the isolates. A suspension of conidia (concentration: 1 ? 108 conidia/ml) was sprayed on healthy adults of C. arcuata on moss patches. Results showed no difference in mortality rates between the isolates (96?97%), but one isolate produced a mycosis of 49% compared to 32% of the other isolate, with 4% of mycosis in control. The results presented here demonstrate this fungus as an antagonist, and indicate it as a potential candidate for future biological control of this invasive pest.