Current and prospective insect agents for the biological control of Parthenium hysterophorus

Current and prospective insect agents for the biological control of Parthenium hysterophorus
Lorraine Strathie, Andrew McConnachie, Milly Gareeb, Sakhi Sambo
Agricultural Research Council – Plant Protection Research Institute

Parthenium hysterophorus (Asteraceae: Heliantheae; parthenium) continues to increase in spread and abundance in South Africa and further afield on the African continent, with growing concern from land managers due to the plant’s detrimental impacts. In 2013, following research in quarantine, the stem-boring weevil Listronotus setosipennis (Coleoptera: Curculionidae) and the leaf-feeding beetle Zygogramma bicolorata (Coleoptera: Chrysomelidae), were approved for release as bio-control agents. Both agents were reared in large numbers and more than 90 releases were conducted during the 2013-2014 growth season in KwaZulu-Natal and Mpumalanga provinces, where parthenium is most invasive. Field results from the first release season were promising with regards to agent persistence and early levels of damage observed. As additional agents will be required to provide optimal biological control of parthenium, three other insect agents are also under consideration. These include the seed-feeding weevil Smicronyx lutulentus (Coleoptera: Curculionidae) for which the host range research has been completed, the stem-galling moth Epiblema strenuana (Lepidoptera: Tortricidae) for which there are host range complications, and the root-crown feeding moth Carmenta sp. nr. ithacae (Lepidoptera: Sesiidae) which has been imported very recently into quarantine. Progress with these insect agents and their contribution to the biological control of parthenium in South Africa is discussed.