Biology and ecology of Ceratitis rosa and Ceratitis quilicii (Diptera: Tephritidae) in citrus
Ceratitis rosa Karsch s. l. (Diptera: Tephritidae), an indigenous pest of commercial fruit including citrus in South Africa, belongs to a complex of cryptic species (Ceratitis FAR). Ceratitis rosa s.l. was recently split into C. rosa and Ceratitis quilicii De Meyer, Mwatawala & Virgilio. The recent description of a new species in the FAR complex impacts the pre- and postharvest management of this species complex in South Africa. In light of the species split and the lack of specific information on each of these species, this study was conducted to determine: (1) the relevant abundance of these species in citrus in the northern parts of South Africa, (2) how effective attractant-based traps in citrus orchards are to these species, and (3) the rate of larval development in fruit of different citrus types. Traps baited with three types of attractants (EGO Pherolure, Capilure (male lures), and three-component Biolure (food-based attractant)) were set out in orchards on nine farms, for a period of one year, in the northern parts of South Africa. Males of the two species were distinguished morphologically, whereas the females were identified using microsatellite markers. Larval development of C. rosa and C. quilicii were compared in Citrus limon, C. paradisi, C. reticulata and C. sinensis. Eggs were artificially inoculated into fruit of each citrus type and larval development assessed daily over 15 days, by dissecting sub-samples of the infested fruit. Ceratitis quilicii were more abundant than C. rosa through almost all of the study areas and C. quilicii appeared to tolerate a wider temperature regime than C. rosa. Ceratitis rosa was negatively affected by low temperatures. EGO Pherolure and Biolure were effective in trapping both fly species. The ratio between the two fruit fly species was similar, when comparing the male and female catches in C. quilicii dominated areas. The development of these two fruit fly species did not differ in each of the citrus types. There were however differences in larval and pupal survival rates between the species depending on citrus type. For both species, larval development was optimal in C. sinensis and poor in C. reticulata. Ceratitis rosa had higher larval survival rates than C. quilicii in C. limon and C. sinensis. Survival was also highest in C. sinensis and it is the most suitable host to conduct further cold sterilization trials with. The different instars of both species can be exposed on similar days when exposing the fruit to a cold treatment to determine which life stage is the most cold tolerant. Findings in this study contribute to improved management of C. rosa and C. quilicii which are of quarantine importance in Africa by determining: the northern distribution in South Africa, the effectiveness of commercially available traps, and the most susceptible citrus cultivar to use for future cold sterilization work.