Author
Daniella Egli
eglid@arc.agric.za
Agricultural Research Council, Plant Health and Protection
Hilton, South Africa
Coauthors
Lorraine Strathie, Agricultural Research Council, Plant Health and Protection, Hilton, South Africa
Sakhi Sambo, Agricultural Research Council, Plant Health and Protection, Hilton, South Africa
Abstract
Parthenium hysterophorus L. (Asteraceae: Heliantheae) is a severe invader in South Africa, negatively impacting agriculture, biodiversity and human and animal health. To supplement the current levels of biological control on parthenium weed, the root crown-boring moth, Carmenta sp. nr ithacae (Beutenmüller) (Lepidoptera: Sesiidae) is being investigated for its suitability for release in South Africa. Difficulties had been experienced in sustaining cultures of this moth in quarantine for extended periods, and low oviposition occurred during initial testing of earlier importations. Following importation of a substantial starter culture from Australia in 2024, experiments were conducted to determine which factors improved oviposition. The effects on egg production by using a lamp providing heat and light, and the density of plants (two or six), and adult moths (five or ten pairs) per breeding cage were investigated. Oviposition was enhanced with a lamp as well as with six plants and five pairs of moths in gauze cages. Far fewer eggs were laid in treatments with only two plants, regardless of moth numbers. These findings resulted in higher oviposition and improved the design of host-specificity trials. To date, very low numbers of eggs have been laid on only a few of the locally important Asteraceae species that have been evaluated during paired choice tests. Additional host-specificity testing is ongoing, with these results discussed.
Keywords
biological control
host range tests
oviposition behaviour
Parthenium hysterophorus
Highlights
The parthenium biocontrol programme in South Africa requires additional agents to improve outcomes.
Altered rearing designs resulted in higher oviposition by Carmenta sp. nr ithacae.
Preliminary host range results show promise.