Effect of constant temperatures on germination, radial growth and virulence of Metarhizium anisopliae to three species of African tephritid fruit flies

The effect of temperatureon conidial germination, mycelial growth, andsusceptibility of adults of three tephritidfruit flies, Ceratitis capitata(Wiedemann), C. fasciventris (Bezzi) andC. cosyra (Walker) to six isolatesof Metarhizium anisopliae were studied inthe laboratory. There were significantdifferences among the isolates in the effect oftemperature on both germination and growth.Over 80% of conidia germinated at 20, 25 and30°C, while between 26 and 67% conidiagerminated at 35°C and less than 10% at15°C within 24 hours. Radial growth was slowat 15°C and 35°C with all of theisolates. The optimum temperature forgermination and mycelial growth was 25°C. Mortality caused by the six fungal isolatesagainst the three fruit fly species varied withtemperature, isolate, and fruit fly species.Fungal isolates were more effective at 25, 30and 35°C than at 20°C. The LT₉₀values decreased with increasing temperature upto the optimum temperature of 30°C. Therewere significant differences in susceptibilitybetween fly species to fungal infection at allthe temperatures tested.