Robinia pseudoacacia, (Black locust) the problem and available solutions

Robinia pseudoacacia, (Black locust) the problem and available solutions
Grant Martin
Rhodes University

Robinia pseudoacacia L. (Fabaceae) is a deciduous tree indigenous to North America that was probably introduced into South Africa via the horticultural industry. Having already established in all nine provinces, it is regarded as one of our most difficult invaders to control as it suckers profusely and readily produces copious numbers of seed. Not only is it a prolific water user, capable of invading pristine environments, but it is also poisonous to both humans and animals. Thorny, dense thickets and difficult-to-navigate mountain terrain make mechanical and chemical control options inadvisable. The aim of the study is to investigate possible biological control options for the management of the tree. In its indigenous range the natural enemies of R. pseudoacacia are well studied and include a variety  of  insects  and  pathogens.  Three  of  these  insects  have  already  established  on  R. pseudoacacia populations in Europe and have proved to be damaging, they include a gracillariid leaf- mining moth, Phyllonorycter robiniella, a cecidomyiid gall midge, Obolodiplosis robiniae (Haldeman) and the locust borer, Megacyllene robiniae forster (Cerambycidae).The locust borer is only known to attack R. pseudoacacia and its cultivars and appears to be the most damaging and promising agent for biological control. Biological control success in other countries, the absence of indigenous Robinia species in South Africa, availability of biological control agents and value to primary industry and horticulture suggest that biological control should be considered for the control of R. pseudoacacia