The occurrence of deuteromycetous entomopathogenic fungi was determined by examining 224 soil samples from 19 locations in three climatic zones of Mauritius. Three sites were sampled per location: one site under vegetables cultivation, one site under sugar cane plantation and one natural site each within 1 km of each other. Soil samples were baited with the waxmoth larvae Galleria mellonella L. and incubated in the dark at 15, 20, 25 or 30°C for 7, 14 and 21 days. Entomopathogenic fungi were isolated from 77 out of 224 (38.6%) soil samples. Metarhizium anisopliae was isolated from 42 (18.8%) samples, Beauveria bassiana from 24 (10.7%), Metarhizium spp. and Paecilomyces fumosoroseus from 5 (2.2%) each and Beauveria spp. from 1 (0.4%). It was observed that M. anisopliae was isolated more frequently from soils under vegetables as compared to soils under sugarcane or habitat with natural vegetation. Beauveria bassiana was isolated more frequently at the lowest incubation temperature (15°C) while M. anisopliae isolates were recovered more frequently at higher temperatures (25 and 30°C). The pathogenicity of seven isolates of M. anisopliae, five isolates of B. bassiana and two isolates of P. fumosoroseus towards the adults of Bactrocera zonata and Bactrocera cucurbitae was tested by topical application of conidial suspension of 1 × 106 conidia/ml. All the isolates tested were pathogenic to the two fruit fly species. Mortality of B. zonata varied between 12.0 and 98.0% and between 2.0 and 94.0% in B. cucurbitae at 5 days post‐treatment. Our results suggest that entomopathogenic fungi present locally, could be integrated for the control of B. zonata and B. cucurbitae.

BackgroundThe South West Indian Ocean (SWIO) archipelagos and Madagascar constitute a hotspot of biodiversity with a high rate of endemism. In this area, the endemic subspecies A. m. unicolor has been described in Madagascar. It belongs to the African lineage, one of the four described evolutionary lineages in honey bees. Despite a long beekeeping tradition and several recorded European introductions, few studies have been carried out on the diversity and proportion of honey bee subspecies.In order to identify and define which evolutionary lineages and potential sub-lineages are present in the SWIO, the COI-COII intergenic region and the ND2 gene of the mtDNA were sequenced in honey bee colonies from three archipelagos. An extensive sampling (n = 1184 colonies) was done in the Mascarene (La Réunion, Mauritius, Rodrigues), Seychelles (Mahé, Praslin, La Digue) and Comoros (Grande Comore, Mohéli, Anjouan, Mayotte) archipelagos. Islands genetic diversity was compared to newly sampled populations from Madagascar, continental African and European populations.ResultsAfrican lineage haplotypes were found in all islands (except for Rodrigues). Madagascar, Comoros and Seychelles had 100% of A lineage, 95.5% in La Réunion and 56.1% in Mauritius. Among all African colonies detected in the SWIO, 98.1% (n = 633) of COI-COII haplotypes described the presence of the subspecies A. M. unicolor. Both genetic markers revealed i) a new private AI mitochondrial group shared by the SWIO archipelagos and Madagascar distant from continental populations; ii) the private African haplotypes for each island suggested diversity radiation in the archipelagos; iii) the detection of the Comoros archipelago as a possible contact area between insular and continental African populations.The exotic European C and M lineages were only detected in the Mascarene archipelago, but striking differences of proportion were observed among islands. Merely 4.6% of European colonies were found in La Réunion whereas Mauritius cumulated 44%. Here, among the 84 observed COI-COII haplotypes, 50 were newly described including 13 which were private to the SWIO archipelagos and Madagascar. Similarly, 24 of the 34 found ND2 haplotypes were novel which included six haplotypes particular to the SWIO populations.ConclusionA new African subgroup was described in the SWIO region with mitochondrial genetic evidence that A. m. unicolor is the indigenous subspecies of the archipelagos surrounding Madagascar.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-017-0520-8) contains supplementary material, which is available to authorized users.

In Mauritius, the peach fruit fly, Bactrocera zonata Saunders (Diptera: Tephritidae), and the melon fly, Bactrocera cucurbitae (Coquillett), are the major pest of fruits and vegetables, respectively. Fruit growers make use of broad-spectrum insecticides to protect their crops from fruit fly attack. This method of fruit fly control is hazardous to the environment and is a threat to beneficial insects. The entomopathogenic fungus, Metarhizium anisopliae (Metchnikoff) Sorokin (Hypocreales: Clavicipitaceae), which was isolated from the soils of Mauritius, was used to investigate whether fungus-treated adult fruit flies could transfer conidia to non-treated flies during mating, and whether fungal infection could have an effect on mating behavior, fecundity, and fertility of the two female fruit fly species. When treated male flies were maintained together with non-treated female flies, they were able to transmit infection to untreated females, resulting in high mortalities. Similarly, fungus-infected female flies mixed with untreated males also transmitted infections to males, also resulting in high mortalities. Infection by M. anisopliae also resulted in the reduction of the number of eggs produced by females of B. cucurbitae. The results suggest that M anisopliae may have potential for use in integrated control programs of B. zonata and B. cucurbitae using the sterile insect technique in Mauritius.

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Field cage tests were carried out to determine the mating compatibility of sterile and wild melon fly, Bactrocera cucurbitae (Coquillett), males that were treated or not treated with entomopathogenic fungi. The melon flies were irradiated at 70 Gy, and the adults were treated with dry conidia of either Beauveria bassiana (Balsamo) or Metarhizium anisopliae (Metchnikoff) Sorokin 1 day before the mating test. Our results demonstrate that sterile melon flies treated with either B. bassiana or M. anisopliae showed mating compatibility with the wild flies. Inoculation of the flies with the fungi did not significantly affect the mean time of copulation (323–567 min) as compared to mating involving only wild flies (407–518 min). Treatment of the flies with either B. bassiana or M. anisopliae did not significantly affect the propensity of mating. Wild females mated indiscriminately with sterile, sterile B. bassiana‐treated or sterile M. anisopliae‐treated males. Irrespective of the treatment combinations, mean percentage remating was significantly higher for sterile females with sterile males (7.72–27.12%) as compared to wild females with sterile males (0.76–14.90%). The possibility of using sterile melon flies as vectors of the entomopathogenic fungi to enhance an SIT programme is discussed.

Distinct host ranges of the melon fly, Bactrocera cucurbitae (Coquillett), have been reported among different island populations, suggesting significant genetic divergence. Thus, for the application of the sterile insect technique (SIT), it is important to ensure that released flies are sexually fully compatible with each other and with the laboratory strains. Mating tests among the following strains of the melon fly, B. cucurbitae: Mauritius laboratory‐adapted (35 generations), Seychelles laboratory‐adapted (24 generations), and Hawaii genetic sexing strain (90 generations), were conducted in field cages at the FAO/IAEA Agriculture and Biotechnology Laboratories in Seibersdorf, Austria during the months of August/September 2009. The genetic sexing strain, developed in Hawaii in 2001, allows separation of females and males on the basis of pupal colour. Two separate series of trials were run simultaneously. In the first, melon fly females from Mauritius were the target strain and the competing males were from Mauritius, Seychelles, and Hawaii (GSS). In the second trial, melon fly females from the Seychelles selected among competing males from the same three populations. Sexual activity was similar among the melon fly populations and no significant non‐random, assortative mating was observed. Therefore, it is suggested that melon flies from Mauritius, Seychelles and the Hawaii are compatible, at least under semi‐natural conditions.

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