Development of Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) on six North American Opuntia species

Abstract

Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) has been used as a biological control agent of several Opuntia species around the world and is widely assumed to be a generalist on host plants within the genus Opuntia. The recent arrival and spread of C. cactorum on the North American mainland has raised concerns for the native species of Opuntia that are being utilized as hosts by the moth. To confirm that C. cactorum is a threat to a wide range of Opuntia species in North America, the host range of the moths was scrutinized in South Africa, where larval development could be monitored on several Opuntia species under natural conditions. Development was monitored on Opuntia ficus-indica L. Miller, O. engelmannii Salm-Dyke, O. fulgida Englm, O. imbricata (Haworth) de Candolle, O. stricta Haworth and O. leucotrichta DC. Larval survival, egg to pupation, was highest on O. ficus-indica (79.2 %) followed by O. engelmannii (57.5 %), O. stricta (55.0 %), O. leucotrichta (29.2 %), O. fulgida (24.2 %) and O. imbricata (16.7 %). Male and female pupal mass was highest, and duration of development shortest on O. ficus-indica. In adult multi-choice oviposition trials, females laid significantly more egg sticks on O. ficusindica than on the other species. Although O. ficus-indica is the preferred host for C. cactorum in South Africa, the moth is nevertheless able to utilize several other species of Opuntia as hosts.