Effect of previous feeding by Falconia intermedia (Hemiptera: Miridae) on subsequent feeding activity on the invasive shrub Lantana camara (Verbenaceae)

摘要

After initially building up to high densities, populations of a promising biological control agent, Falconia intermedia (Distant) (Hemiptera: Miridae), imported to control the invasive plant Lantana camara L. (Verbenaceae) in South Africa, disappeared at almost all release sites in the Eastern Cape, Mpumalanga, KwaZulu-Natal and Limpopo provinces. In an attempt to explain this phenomenon, laboratory trials were conducted to determine the effect of previous feeding on the subsequent performance of F. intermedia on L. camara varieties from two of the Eastern Cape release sites; Lyndhurst Farm and Whitney Farm. F. intermedia feeding damage, number of adults, number of nymphs and oviposition on Whitney Farm, L. camara plants were 40.8% (p<0.001), 106% (p<0.001), 81.5% (p<0.001) and 80% (p<0.001) higher, respectively, than on Lyndhurst Farm, indicating the superior suitability and quality of Whitney Farm plants for F. intermedia performance. A defence response was observed by plants from Lyndhurst Farm that were previously fed on (i.e. induced). The induced plants had significantly lower F. intermedia feeding damage (21.4% less, p=0.007), numbers of adults (187.5% less, p=0.034), numbers of nymphs (110% less, p=0.071) and oviposition (99.8% less, p=0.021) than plants that were not previously fed on. The defence responses were elicited and expressed throughout the plant in both damaged and undamaged leaves within five weeks after insect release (rapidly induced response). The significant decrease in herbivore performance suggests that some L. camara varieties possess factors that enable them to resist subsequent feeding activity, offering us some understanding of one of the factors that might have contributed to the failure of F. intermedia in South Africa.