Efficacy of Different Entomopathogenic Fungal Isolates against the Pine Processionary Moths Thaumetopoea pityocampa Denis Schiffermüller and Thaumetopoea wilkinsoni Tams

Pine processionary moths Thaumetopoea pityocampa and Thaumetopoea wilkinsoni are among the most harmful insects that cause severe damage to pine forests in many countries, including Türkiye. The aim of this study was to evaluate the efficacy of entomopathogenic fungi (EPF) isolates of Beauveria bassiana (PA-4 and KTU-24), Metarhizium anisopliae (KTU-51), and M. floviridae (AS-2) against the 2nd instar larvae of T. pityocampa and T. wilkinsoni under laboratory conditions. T. wilkinsoni eggs were collected from pine trees at Ondokuz Mayıs University Kurupelit Campus in Samsun, Türkiye, in 2021, while T. pityocampa eggs were collected from Kahramanmaraş province, Türkiye, in 2021, and the 2nd instar larvae were used for the experiment. Four fungal isolates were sprayed on the larvae at 2 mL for each concentration (1 × 105 - 1 × 108 conidia mL-1). At a concentration of 1 × 108 conidia mL-1, mortality rates for T. pityocampa larvae were 55.6-100%, while mortality rates for T. wilkinsoni larvae were 56.8-100%. It was found that two isolates of B. bassiana were virulent for both T. pityocampa and T. wilkinsoni, and the KTU-24 isolate was the most virulent isolate, causing the lowest LC50 values ​​​​(2.2 × 105 for T. pityocampa and 4.3 × 105 for T. wilkinsoni) and the shortest mean survival time for both larval species. It is suggested that the KTU-24 isolate can be used in the biological control of pine processionary moth species.