The tortoise beetle Physonota maculiventris (Chrysomelidae: Cassidinae) is suitable for release against the weedy Mexican sunflower Tithonia diversifolia (Asteraceae) in South Africa.

The biology and host range of the defoliating beetlePhysonota maculiventrisBoheman (Chrysomelidae: Cassidinae) were studied in quarantine to determine its suitability for release as a biological control agent against Mexican sunflower,Tithonia diversifolia(Hemsl.) A. Gray (Asteraceae), in South Africa. Females laid 5.25 ± 0.25 (mean ± SE) egg batches during their lifetimes, with each batch consisting of approximately 33 eggs. Larvae were highly gregarious as early instars and both larvae and adults fed voraciously, often defoliating the plants completely. The life cycle of the beetle was completed in 67.5 ± 7.5 days under quarantine conditions. Among the 58 test plant species subjected to no-choice tests,P. maculiventrisdeveloped successfully onT. diversifoliaand some sunflower (Helianthus annuusL.) cultivars. However, only minor damage was recorded on non-target species, notably the exotic weedXanthium strumariumL. and someH. annuuscultivars. Also, survival to adulthood was considerably lower on sunflower cultivars than on the target weed during these tests. During choice tests,P. maculiventrisoviposited and developed successfully onT. diversifoliaonly, with only minor feeding damage on someH. annuuscultivars, suggesting that the beetle’s field host range will be confined to the target weed. Risk analysis also showed thatP. maculiventrispresents an extremely low risk to non-target plant species (e.g. within the tribe Heliantheae and other close relatives). The study concluded thatP. maculiventrisis safe for release in South Africa and an application for its release is being considered by the relevant South African regulatory authorities. [ABSTRACT FROM PUBLISHER]