The host range of four new biotypes of Dactylopius tomentosus (Hemiptera: Dactylopiidae) from southern USA and their potential as biological control agents of Cylindropuntia spp. (Cactaceae) in Australia: Part II

Abstract

ABSTRACTEight Cylindropuntia species have naturalised in Australia and pose serious economic, environmental and social impacts. The host range of four additional biotypes of D. tomentosus from southern USA was investigated. Feeding and development were restricted to the genus Cylindropuntia. However, they showed differences in specificity within this genus and some biotypes discriminated between the provenances of Cylindropuntia rosea and Cylindropuntia tunicata. Efficacy trials were conducted to determine whether populations of each biotype could be sustained on the naturalised Cylindropuntia species and if these populations could retard the growth or kill these plants. The ‘acanthocarpa’ biotype offers potential control of C. rosea (Lorne Station), while the ‘cylindropuntia sp.’ biotype shows great potential to control C. rosea (Grawin). The ‘cylindropuntia sp.’ biotype also had a high impact on Cylindropuntia kleiniae and Cylindropuntia imbricata, and a moderate impact on Cylindropuntia leptocaulis and Cylindropuntia prolifera. The ‘acanthocarpa × echinocarpa’ biotype had its greatest impact on C. tunicata (Grawin), killing this plant in 18 weeks. A fourth biotype, ‘leptocaulis’, was damaging to some species, but was less effective than the other biotypes. Cylindropuntia spinosior is the only naturalised species in Australia where no effective biocontrol agent has been found.