The host specificity of Trabutina mannipara (Hemprich & Ehrenberg, 1829) (Homoptera: Coccoidea: Pseudococcoidae): a potential biocontrol agent of invasive Tamarix chinensis (Lour) and T. ramosissima (Ledeb) in South Africa.

Abstract

ABSTRACT Tamarix (Tamaricaceae), a phreatophyte genus from the Old World, is a tenacious competitor which has invaded North America (namely the United States and Mexico), Australia, and South Africa amongst other countries. Biological control of invasive Tamarix taxa in South Africa is complicated by the indigenous T. usneoides, which is phylogenetically distant from the invasive T. chinensis and T. ramosissima. This suggests the possibility of finding a host specific biological control agent. Trabutina mannipara underwent laboratory-based host specificity trials. During no-choice testing, T. mannipara showed no difference in host range selection as there was no significant difference in the settling and developmental rate on all Tamarix taxa tested. These undesirable non-target effects on the indigenous species led us to reject T. mannipara as a potential biological control agent of invasive Tamarix taxa. We examined the possibility of secondary metabolites being a factor in the feeding choice of T. mannipara, but no significant difference in the bark tannin levels was found between the above Tamarix taxa. Further investigation of plant secondary metabolites, used for defense against insect herbivory, may however, assist in the selection of biological control agents against invasive Tamarix in South Africa.