Parasitoid diversity associated with Phoracantha semipunctata and Phoracantha recurva in South African Eucalyptus plantations

Le résumé fourni par la source

Phoracantha semipunctata Fabricius and Phoracantha recurva Newman (Coleoptera: Cerambycidae) are xylophagous beetles, native to Australia, that infest Eucalyptus trees in the native and invasive range. Outbreaks of Phoracantha species are associated with drought stress, so climate change is predicted to increase the frequency of outbreaks and elevate the importance of this pest for Eucalyptus plantation forestry. Although biological control agents were released in the Western Cape, Limpopo, and parts of Mpumalanga provinces from 1910 to 1995, it is unclear if they established successfully in the key forestry hubs of Mpumalanga and KwaZulu-Natal. Knowledge on the diversity and distribution of the parasitoids of the two Phoracantha species in South Africa is important to inform future biological control initiatives, given the potential future importance of Eucalyptus pests. The aim of the study was to determine the distribution of P. recurva and P. semipunctata in the main Eucalyptus production regions and identify the parasitoids associated with them. Logs were collected from infested trees (fallen and living), placed in insect rearing cages and emerging insects identified based on morphology. Both species of Phoracantha were present, with P. recurva emerging in higher numbers. Twelve species of parasitoids emerged from the infested logs. These included the egg parasitoid, Oobius longoi (Siscaro) (Hymenoptera: Encyrtidae) and the larval parasitoid Syngaster lepidus Brullé (Hymenoptera: Braconidae), previously released in South Africa and have now spread throughout the main Eucalyptus production region. Novel associations of native parasitoids with Phoracantha were also identified, but further studies are required to determine their ecological role.

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