Survival and dispersal of the stem-boring weevil, Listronotus setosipennis, and the leaf-feeding beetle, Zygogramma bicolorata, one year after their release for the control of the invasive weed, Parthenium hysterophorus, at two locations in Ethiopia.
The presence and spread of Listronotus setosipennis (Coleoptera: Curculionidae) and Zygogramma bicolorata (Coleoptera: Chrysomelidae) released in 2017 for the control of Parthenium hysterophorus (L.) (Asteraceae: Heliantheae) at two locations in Ethiopia (Arba Minch and Mojo) were assessed twice (July, September) in 2018. At Arba Minch, no L. setosipennis was found, only Z. bicolorata established and the number of eggs varied from 1.4±0.71/plant (July) to 7.41±4.52/plant (September) at the release site and from 0.52±0.18/plant (July) and 0.68±0.24/plant (September) at the dispersal site. At Mojo, only L. setosipennis established with 3.87±1.18 eggs/plant (July) at the release spot and 10.76±1.64 eggs/plant in September whereas after dispersal the eggs numbered 8.69±3.2/plant (July) and 14.98±1.73/plant (September). After one year, L. setosipennis and Z. bicolorata were found 51.75±3.95 m and 94.15±13.66 m away from the release spots, respectively. The results show that the biocontrol agents have started to establish and have dispersed at the two locations in Ethiopia.