Host species, age and sex as factors affecting the susceptibility of the African Tephritid fruit fly species, Ceratitis capitata, C. cosyra and C. fasciventris to infection by Metarhizium anisopliae

Abstract

The effect of host age and sex on the susceptibility of 3 tephritid fruit fly species, Ceratitis capitata (Wiedemann), C. cosyra (Walker) and C. fasciventris (Bezzi) to the entomopathogenic fungus Metarhizium anisopliae (Metchnikoff) Sorokin was studied in the laboratory. Three adult host ages, 0 (<1 day-old), 7-day-old and 14-day-old, were used. All 3 species were susceptible to fungal infection, although there were differences in the levels of susceptibility among the hosts. Age accounted for the largest variability in mortality followed by species, while sex had the lowest variability. Of the 3 host ages tested, the 0- and 7-day-old flies were more susceptible to fungal infection than the 14-day-old flies. Male and female C. fasciventris flies generally succumbed earlier to fungal infection than the other two species. Female flies of C. cosyra and C. fasciventris were also generally more susceptible to fungal infection than the males, although differences were apparent at 3 and 4 days after treatment but not 5 days after treatment. Age accounted for the largest variability in lethal time mortality values (LTs). Mean LT-values generally indicated that the speed of kill was faster among younger flies than the older flies. LT95 ranged between 3.9–4.9 days in the 0-day-old flies, 4.3–6.1 days in the 7-day-old flies and 4.6–6.1 days in 14-day-old flies in the different species and sexes. The implication of this study for the management of fruit flies is discussed.