Ten economically important species belonging to the Tephritidae have been recorded in Union of the Comoros (an island nation off the coast of East Africa). Little is known about the distribution of these species and how they are affected by climatic factors in the Comoros archipelago. The main objectives of this study were to characterize: (i) the population dynamics of tephritid fruit flies in relation to season and host fruit availability and (ii) the geographic distribution of tephritids in relation to temperature and rainfall. The study was conducted during 2 years at 11 sites on three islands (Grande Comore, Anjouan, and Mohéli) in the archipelago. The site elevations ranged from 55 to 885 m a.s.l. At each site, flies were collected weekly in eight traps (four different lures, each replicated twice). Fruit phenology was also recorded weekly. The dominant tephritid species detected was the invasive Bactrocera dorsalis Hendel followed by Ceratitis capitata Wiedemann. Tephritid species were generally more abundant during the hot and rainy seasons than during the cold and dry seasons. Bactrocera dorsalis numbers were higher on Grande Comore than on the two other islands. On Anjouan and Mohéli, B. dorsalis numbers were very low in 2014 but sharply increased in 2015, suggesting a recent invasion of these islands. Abundances were significantly related to the fruiting of mango, strawberry guava, and guava for B. dorsalis and to the fruiting of mango, guava, and mandarin for C. capitata. Bactrocera dorsalis was more abundant in hot and humid low-altitude areas, while C. capitata was more abundant in dry medium-altitude areas, suggesting the occurrence of climatic niche partitioning between the two species.
Drosophila suzukii (Matsumura, 1931) is an Asian pest of grapes and other soft fruits that has invaded North America and Europe during the last decade. Here we report its recent occurrence in two islands of the Comoros archipelago in the Mozambique Channel, namely Mayotte and Ngazidja (Grande Comore), in April 2017 and November 2018, respectively. We also document its absence from other African islands of the Mozambique Channel and the Western Indian Ocean including Mayotte until 2013.Drosophila ashburneri Tsacas, 1984 is the only member of the suzukii species subgroup known from the Comoros, but it is morphologically distinct and likely distantly related to D. suzukii. Drosophila suzukii has likely been recently introduced to the Comoros archipelago, perhaps from La Réunion island where it first appeared in November 2013.In all these tropical islands, D. suzukii was found in high-altitude habitats in agreement with its adaptation to cold environments. These results suggest the high susceptibility of highlands in Eastern and Southern Africa to be infested by this pest in a near future.
Knowledge of the host range of a biocontrol agent (BCA) is fundamental. Host range determines the BCA’s economic potential, as well as the possible risk for non-target organisms. Entomopathogenic fungal strains belonging to the genus Beauveria are widely used as BCA, but our knowledge of their physiological host range is only partial. The aim of this study was to improve our understanding of the physiological host range of three Beauveria strains belonging to two species, B. hoplocheli and B. bassiana. We performed laboratory mortality bioassays to assess their pathogenicity and virulence against nine insect pests, belonging to three orders: Lepidoptera, Coleoptera and Diptera. Mortality rate, mean survival time and mycosis rate were used to estimate virulence. Pathogenicity was assessed as the capacity to cause a disease and induce mortality. Virulence was assessed as the severity of the disease based on mortality rate, mean survival time and mycosis rate. The results of this study revealed significant differences in the physiological host range of the three Beauveria strains tested. The three strains were pathogenic to all Diptera and Lepidoptera species tested. In the case of the Coleoptera, only the B. hoplocheli strain was pathogenic to the white grub Hoplochelus marginalis and only the B. bassiana strains were pathogenic to Alphitobius diaperinus. The B. hoplocheli strain was less virulent on Lepidoptera and Diptera than the two B. bassiana strains. The latter both exhibited very similar virulence patterns. The fact that B. hoplocheli and B. bassiana strains have different host ranges means that they can be used as BCA to target different pests. Impacts on non-target insects across multiple orders cannot be ruled out in the absence of ecological host range studies.
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