Author
Lulama Gracious Madire
Agricultural Research Council – Plant Health and Protection
South Africa
Coauthors
Terence Olckers, University of KwaZulu-Natal, School of Life Sciences, Scottsville, South Africa
Guy Sutton, Centre for Biological Control, Department of Zoology and Entomology, Rhodes University, Makhanda, South Africa
David Simelane, Agricultural Research Council – Plant Health and Protection, South Africa , and University of KwaZulu-Natal, School of Life Sciences, Scottsville, South Africa
Abstract
Biological control practitioners are required to demonstrate an agent’s likelihood of establishing and controlling the target weed. Species distribution modelling has become a popular tool in recent years for predicting potential establishment and distribution of biocontrol agents. The root-feeding flea beetle Heikertingerella sp. (Chrysomelidae), collected in Mexico, was approved as a biocontrol agent against the invasive Tecoma stans (L.) (Bignoniaceae) in South Africa in 2022. Before the release of Heikertingerella sp., a laboratory study was conducted to assess its potential establishment and distribution. MaxEnt modelling was used with the beetle’s critical thermal limits to predict its potential distribution and identify optimal release locations across the weed’s distribution range in South Africa. The model indicated that most of South Africa has a highly suitable climate for the beetle, especially along the eastern and southern coast, where the weed is more common. Only the inland region was predicted to be unsuitable for the beetle. Additionally, the beetle’s thermal physiology, determined by its critical thermal minimum and maximum temperatures, as well as its lower and upper lethal temperatures, suggests that the beetle can tolerate temperature extremes in at least four provinces within the range of T. stans in South Africa. The beetle is now well-established at one site in the Eastern Cape province, dispersing over 5km during a 2-year period.
keywords
Establishment
MaxEnt modelling
Root-feeding flea beetle
Thermal physiology
Weed biocontrol
Highlights
MaxEnt model indicated that most of South Africa has a highly suitable climate for the beetle.
The beetle is well-established at one site in the Eastern Cape province and is abundant.
In the past two years, the beetle has spread over five kilometers, causing significant damage.