The Prosopis podlet weevil from South America (Coelocephalapion gandolfoi) has long been considered a promising candidate for release as a biological control agent against Prosopis in South Africa. This species lays its eggs within immature Prosopis pods and the developing larvae destroy the young seeds. It is anticipated, that because it damages the seeds before livestock start foraging on the pods, it could have a more substantial impact than the seed feeding beetles already introduced against Prosopis in South Africa. Testing, over several years, to ensure that the Prosopis podlet weevil is safe for release in South Africa was completed in 2019 and it was subsequently approved for release. It causes extensive seed loss in Argentina and it is hoped that the same will occur here. For more information on the life cycle of this weevil visit: https://www.ru.ac.za/centreforb.../resources/otherresources/
Our colleagues led by Fernando McKay at the Fundación para el Estudio de Especies Invasivas (FuEDEI) in Buenos Aires, Argentina obtained permission from the Secretaría de Ambiente de La Rioja to collect weevils for export to South Africa and National Argentinian authorities provided the requisite export permits.
FuEDEI succeeded in collecting substantial numbers of the weevils and these were shipped to South Africa earlier this month. The shipment was received by the CBC’s Carien Kleinjan and Blair Cowie who prepared the beetles for release at several sites in the Northern Cape. The weevil’s epic journey from collecting in Argentina, transit through the quarantine facility at the University of the Witwatersrand and finally their liberation in South Africa, is illustrated in the accompanying images.
Ultimately a total of 600 healthy, active weevils were released across 5 sites in the Karoo. It was necessary that immature Prosopis pods were available at the sites and suitable sites were selected based on accessibility and feedback from farmers subscribing to the “Prosopis beheer” WhatsApp group.
The release of the weevils marks significant progress, but several hurdles remain. The weevils now need to survive and lay eggs to produce a new generation of adults that will emerge in about 4 months’ time. They then need to survive the winter in order to breed again during the 2022 podding season. The pods develop very distinctive scars where eggs have been laid and the adults leave a distinctive round hole when they emerge from the pod. These details will be used by researchers to evaluate the progress being made by this weevil towards becoming established in South Africa. Progress, or lack thereof, will be reported to the landowners concerned and the broader Prosopis community.