Native range host-specificity and impact studies of Osphilia tenuipes Fairmaire (Coleoptera, Curculionidae): a potential biocontrol agent for Kalanchoe delagoensis (Crassulaceae) in Australia

ABSTRACT

Kalanchoe delagoensis Eckl. & J.Zeyh. (Crassulaceae, mother-of-millions) is a plant endemic to Madagascar which was introduced to, and became invasive in, Australia. The stem-boring weevil Osphilia tenuipes Fairmaire (Coleoptera, Curculionidae) is a natural enemy of K. delagoensis in Madagascar. A laboratory culture of this insect was established from field collections in the south of Madagascar, and its potential as a biocontrol agent for Australia was assessed under natural field conditions in Madagascar. The host range of O. tenuipes (open and closed multiple-choice tests, and a multi-generational trial) was examined with seven Kalanchoe spp. and one Echeveria sp. These trials demonstrated that O. tenuipes was oligophagous. However, oviposition and development of immature stages through to adults were recorded on two species of interest for Australia, Kalanchoe spathulata DC. and Kalanchoe blossfeldiana Poelln (Crassulaceae). The multi-generational trials showed that O. tenuipes completed five generations on K. spathulata and K. blossfeldiana. Emergence and survival of adults on controls (K. delagoensis) and the three species tested were significantly different. Osphilia tenuipes adult weights were not significantly different (for species and generations). Adult survival after 30 days was significantly higheron K. delagoensis compared to K. blossfeldiana and K. spathulata. The weevil significantly reduced the numbers of phyllodes and bulbils and overall plant biomass of K. delagoensis. It was evident that O. tenuipes is a damaging, oligophagous insect with significant promise as a potential biocontrol agent for K. delagoensis in Australia.

KEYWORDS:

• Bryophyllum delagoense
• host range
• weed biological control

Acknowledgements

We wish to thank Jean Claude Rakotonirina, Herisolo Andriniaina Razafindraleva for valuable advice on insect rearing and Jean Jacques Rasamoelina for his help in maintaining plant and insect cultures. We thank Fisikina Hatolinay Tovonaiko and all teams at the Solohotse Association for field assistance in the south of Madagascar. The Ministry of Forests (Madagascar) is thanked for the facilitation of collection and research permits. Bernie Dominiak reviewed a pre-submission version of the manuscript. We thank the Ministry of Environment and Sustainable Development of Madagascar for the issuing of collection permits (N°264/16/MEEF/SG/DGF/DAP/SCB.Re, N°256/17/MEEF/SG/DGF/DAP/SCB.Re, N°210/18/MEEF/SG/DGF/DAP/SCB.Re and N° 239/19/MEDD/SG/DGEF/DGRNE) which enabled the legal collection of both insect and plant material from the field. Bernie Dominiak, Bill Palmer and Kunjipatham Dhileepan are thanked for their constructive reviews of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Financial support for this programme was provided by Agrifutures and the Australian Department of Agriculture, Water and the Environment under their Rural Research and Development for Profit Programme (Round 2) (RnD4Profit-15-02-005; PRJ-01537), the New South Wales Department of Primary Industries and Regional Development (Biosecurity and Food Safety) and the New South Wales Weed Biocontrol Taskforce.