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

The effect of temperature on conidial germination, mycelial growth, and susceptibility of adults of three tephritid fruit flies, Ceratitis capitata ( Wiedemann), C. fasciventris (Bezzi) and C. cosyra ( Walker) to six isolates of Metarhizium anisopliae were studied in the laboratory. There were significant differences among the isolates in the effect of temperature on both germination and growth. Over 80% of conidia germinated at 20, 25 and 30 degreesC, while between 26 and 67% conidia germinated at 35 degreesC and less than 10% at 15 degreesC within 24 hours. Radial growth was slow at 15 degreesC and 35 degreesC with all of the isolates. The optimum temperature for germination and mycelial growth was 25 degreesC. Mortality caused by the six fungal isolates against the three fruit fly species varied with temperature, isolate, and fruit fly species. Fungal isolates were more effective at 25, 30 and 35 degreesC than at 20 degreesC. The LT90 values decreased with increasing temperature up to the optimum temperature of 30 degreesC. There were significant differences in susceptibility between fly species to fungal infection at all the temperatures tested.