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Results and Discussion

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1 Results and Discussion
THE USE OF ENTOMOPATHOGENIC FUNGI TO CONTROL INVASIVE WASPS IN THE WESTERN CAPE REGION Mhlongwe, T.R.1, Veldtman, R.2 and Jacobs, K.1 1Microbiology Department, Stellenbosch University, Private Bag X1, Matieland, 7602. 2Department of Conservation Ecology & Entomology, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa Introduction Invasive species, which can be microbes, plants and animals that are introduced to a new region and successfully establish, and pose serious social, economic and ecological threats (Manfredini et al, 2013). Polistes dominula, also known as European yellow jackets, is native to Mediterranean Europe. These insects have spread and become invasive in five continents including the Americas, Asia, Canada, Europe and Africa (Veldtman et al., 2012). The first record of P. dominula in South Africa was in 2008 in Kuilsriver and from there they have spread to various parts of the Western Cape. Currently these wasps are considered to be localised in the Western Cape. There have been different control strategies used to get rid of the rapidly expanding invasive wasp populations, these strategies consist of physical removal, chemical control and biological control. Physical removal not an efficient removal strategy because it is labour intensive an time consuming (Benadé et al, 2014). Chemical control is toxic to the environment and therefore not a desirable control strategy (Beggs et al, 2011). Although Xenos vesparumis a natural enemy of P. dominula, it has not successfully reduced the invasive wasp populations. Due to the failure of the mentioned control methods, there is a dare need to find an effective environmentally safe control strategy. Objective To isolate and evaluate potential fungal isolates that can be used to control P. dominula populations. Results and Discussion A total of 14 Strains were isolated, of which 3 were considered to be potential entomopathogenic species. These were identified as Beauveria bassiana, Beauveria brongniartii and Purpureocillium lilacinum. They were then used in the bioassays. The results of the mean proportional mortality of second instar P. dominula larvae treated with selected fungal isolates at 2 X 109 conidia/ml are presented in figure 2 (A-F). Fungal species varied in their ability to infect P. dominula. Treatment with B. bassiana isolates 4818 and 4849 lead to 100 % mortality four days after exposure. By comparison, treatment with the commercial control strain only lead to 100 % mortality after six days. B.bassiana isolated from the soil was more pathogenic than the insect derived isolates. Sample collection Isolation (selective media) Morphological identification DNA Extraction PCR Sequencing nBLAST Bioassay Materials and methods Wasp larvae were collected from the Welgevallen Experimental farm at Stellenbosch University. Isolations were done as follow: Fig.2 (A-F). Larval mortality of different fungal isolates. Isolate E14 (P. lilacinum), was the least pathogenic, only reaching 100 % mortality after seven days. By comparison, E14 caused 80 % mortality, while the untreated control already had 90 % mortality four days after exposure. P. lilacinum, has been previously developed as a control agent agaisnts aphids but it is not pathogenic to wasps, this shows that P. lilacinum is host specific. It is evident that the commercial strain is not effective against invasive wasp populations, this could be due to the fact that commercial strains are derived from insects and not from soil. Conclusions Several candidate species were isolated during the course of the study. The results show that B. bassiana is the best candidate since it resulted in the highest larval mortality in the shortest period. P. lilacinum seemed to have the least pathogenicity on larvae of P. dominula because larvae treated with P. lilacinum lived longer than those that were untreated. Acknowledgements This research was supported by Grants from the National Research Foundation (NRF) and South African National Biodiversity Institute (SANBI). We also like to thank Carolien van Zyl (Entomology Department) for providing the commercial strain of B. bassiana that was used as a standard for the bioassay. Fig.1. Bioassay, A) 2nd instar larvae in wasps nest. B)Larvae were remove from the cells and C) placed individually on petri-dishes, then the fungal spore suspension was applied on the larvae . D-E) Larval mortality was monitored on a daily basis and fungal growth was observed on treated larvae. References F. Manfredini, C. M. Grozinger and L. Beani, Examining the “evolution of increased competitive ability hypothesis in response to parasites and pathogens in the invasive paper wasp Polistes dominula,"  Naturwissenschaften, vol. 100, pp , 2013. R. Veldtman, P. Addison, G. Tribe, J. Holland, B. Gerowitt, O. Alomar, F. Bianchi, L. Eggenschwiler, M. v. Helden and C. Moonen, Current status and potential future impact of invasive vespid wasps (Vespula germanica and Polistes dominulus) in South Africa.  IOBC/Wprs Bulletin, vol. 75, pp , 2012. P. Benadé, R. Veldtman, M. J. Samways and F. Roets, "Rapid range expansion of the invasive wasp Polistes dominula (Hymenoptera: Vespidae: Polistinae) and first record of parasitoids on this species and the native Polistes marginalis in the Western Cape Province of South Africa: short communication,"  Afr.  Entomol., vol. 22, pp , 2014. J. R. Beggs, E. G. Brockerhoff, J. C. Corley, M. Kenis, M. Masciocchi, F. Muller, Q. Rome and C. Villemant, "Ecological effects and management of invasive alien Vespidae,"  Biocontrol, vol. 56, pp , 2011.


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