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Determining the suitability of a European cone weevil, Pissodes validirostris, for biological control of invasive pines in South Africa
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Edité par CCSD ; CSIRO Publishing -
International audience. Several Mediterranean pine species introduced to South Africa have become invasive plants which displace native flora and deplete limited water resources. A proposal to release host-specific, seeddestroying insects to arrest these pine invasions has created a potential conflict with the lucrative forest industry which is predominantly based on pine species from North America. A survey of European cone insects revealed that pine cones are heavily damaged by larvae of a cone weevil, Pissodes validirostris (Coleoptera: Curculionidae). To determine the host specificity, weevils were collected on 10 pine species throughout Europe. Adult responses to European and North American Pinus species were recorded using both natural choice tests and no-choice tests. Cone use was significantly dependent on the larval host of the weevils with adults originating from northern and alpine pines (P. sylvestris group) being incapable of developing on Mediterranean pines (P. pinaster and P. pinea) and vice versa. Neither group of beetles utilized cones of five-needle pines or P. patula. Observations of adult maturationfeeding on seedlings produced similar patterns of host specificity. Morphometric and genetic (mitochondrial DNA) analyses on the different populations confirmed that P. validirostris probably consists of a complex of sibling species specialized on different host pines rather than a single generalist species. Therefore, cone weevils originating from P. pinaster appear to be suitable for release in South Africa.
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