Suitability of the defoliating beetle Physonota maculiventris (Coleoptera: Chrysomelidae) for release against Tithonia diversifolia (Hemsl.)A.Gray (Asteraceae) in South Africa

Suitability of the defoliating beetle Physonota maculiventris (Coleoptera: Chrysomelidae) for release against Tithonia diversifolia (Hemsl.)A.Gray (Asteraceae) in South Africa
T. E. Mphephu1, 2*, D. O. Simelane1 & T. Olckers2
1Agricultural Research Council-Plant Protection Research Institute, Private Bag X134, Queenswood, 0121 South Africa
2University of Kwazulu-Natal, Private Bag X01, Scottsville, 3209 South Africa

Tithonia diversifolia (Hemsl.)A.Gray (Asteraceae), commonly known as Mexican sunflower, is a perennial bushy plant of Mexican and Central American origin. It has become naturalized in South Africa, particularly in Kwazulu-Natal, Limpopo and Mpumalanga provinces where it has become a problematic aggressive weed. A biological control programme against T. diversifolia was initiated in South Africa in 2007. The tortoise beetle, Physonota maculiventris (Coleoptera: Chrsomelidae), was initially selected as a promising candidate agent and imported into South Africa in 2010 for host- specificity testing in quarantine. Tests carried out on the beetle so far have shown positive results, including severe damage by the adults and immature stages to the plant’s leaves. Physonota maculiventris has a relatively short generation period and highly damaging larval stages. Among the 64 test plant species screened, the beetle has caused only minor damage on two non-target speices. Based on these preliminary results, P. maculiventris appears to be a highly promising agent for T. diversifolia and could provide a solution to the threat posed by this weed in South Africa.