Selecting thermal tolerant strains of entomopathogenic fungi to control Ceratitis capitata (Wiedeman) in tropical semi-arid conditions

• Published in: Biological control 2022-12, Vol.176, p.105062, Article 105062
• Main Authors: Gava, Carlos Alberto Tuão, Leal, Clayton Moreira, Vieira de Sá, Alicia, Paranhos, Beatriz Aguiar Jordão
• Format: Article
• Language: English
• Subjects: Beauveria bassiana; Constant versus variable temperature; Growth and virulence; Metarhizium anisopliae; Thermal tolerance
• ISSN: 1049-9644; 1090-2112
• DOI: 10.1016/j.biocontrol.2022.105062

•Thermal tolerance is an important characteristic of a biocontrol agent.•Applying constant temperature can cause discharging efficient BCAs.•Spore germination, mycelial growth, and insect mortality were different at constant and fluctuating temperature.•Mildly thermotolerant strains under constant high temperature effectively killed adults C. capitata under fluctuating temperature.•Field experiments in two contrasting seasons confirmed this result. Although it is usual, using constant temperature to select thermo-tolerant entomopathogen (EF) strains could discard potentially efficient biocontrol agents (BCA). The objectives of this work were to select virulent EF against C. capitata and evaluate the effect of continual and fluctuating temperature on fungal development and virulence. Initial experiments compared the effect of constant temperatures (CT) (20, 25, 30, 35, and 38 °C) and simulated intraday temperature variation (SIV) (20–38 °C) over conidial germination, mycelial growth, and insect mortality. Temperatures ≥ 35 °C in the CT experiments significantly reduced conidial germination, and the strains of Beauveria bassiana BbLCB81 and BbLCB289 showed the highest conidial germination and mycelial growth. SIV also caused a significant effect, and M. anisopliae MaLCB62 showed the highest conidial germination and mycelial growth. Applying EF strains as toxic baits in CT showed that the highest mortality occurred at 30 °C, and BbLCB62 and BbLCB289 showed the largest insect mortality at 38 °C. Survival analysis showed a slight increase in the average survival time (ST50) at 30 °C. In SIV conditions, MaLCB56 and BbLCB289 were highly virulent. In a field cage experiment at a warmer temperature, BbLCB62 was the most virulent strain according to the M-C test comparing survival curves. However, confirmed accumulated mortality on the 10th day was similar to the moderately tolerant BbLCB289 (Tukey, p