Improving the effectiveness of the release strategy for the array of Dactylopius tomentosus biotypes for the biocontrol of Cylindropuntia species by using DNA analysis

Six biotypes of Dactylopius tomentosus (Lamarck) (Hemiptera: Dactylopiidae) have been imported into Australia as biological control agents to combat the eight naturalised invasive Cylindropuntia species. Each D. tomentosus biotype tested exhibited significant differences in host specificity, host preference and performance across the Cylindropuntia species. Biocontrol success is dependent on the correct identification of the targeted plant species and the correct matching of an insect or pathogen to that plant. An optimal release strategy is to match the most effective biotype to the targeted Cylindropuntia species. Biotype matching to Cylindropuntia species was enhanced through the use of molecular phylogenetic tools and more thorough morphological observations of the cacti species. Molecular studies demonstrated that using two plastid markers (Rpl36-Rps8 spacer region and TrnH-PsbA spacer) and a nuclear region (phosphoenolpyruvate carboxylase) allowed for differentiation of the eight Cylindropuntia species. Molecular analyses using three markers enable the identification of unknown Cylindropuntia species when species identification is not possible using traditional phenological and morphological tools. The genetic identification of the Cylindropuntia provides a time efficient match of target host species and biotype within days rather than the traditional long term host trials (three month life cycle) previously required. Utilising DNA analyses will markedly improve the chance of containment of Cylindropuntia infestations in Australia through better matching of biocontrol agents with their most preferred host.