Biocontrol of thistle cholla cactus, Cylindropuntia pallida : a successful agent in Australia is incompatible with the invasive populations in South Africa

This is the authors' abstract. We don't add key points for this paper.

Cylindropuntia pallida F.M. Knuth (Cactaceae) is an invasive alien species in Australia and South Africa. Two lineages of the cochineal insect Dactylopius tomentosus Lamark were considered as potential biocontrol agents for C. pallida in South Africa. One lineage, referred to as ‘californica var. parkeri’, was collected off Cylindropuntia bernardina (Engelm. ex Parish) (= Cylindropuntia californica var. parkeri (J.M.Coult.) Pinkava) in Mexico, was exported into quarantine in Australia and subsequently released in that country. The second lineage was collected off C. pallida in Mexico and was imported into quarantine in South Africa and is referred to as the ‘pallida’ lineage. Compatibility of the cochineal lineages with invasive C. pallida from South Africa was tested by comparing fitness parameters when reared on either the South African C. pallida or control plants (either Australian C. pallida or Mexican C. pallida). Ten crawlers were inoculated onto each of the controls and the South African cladodes. Measurements were taken to assess fitness, which included female mass, settlement and female fecundity. The ‘californica var. parkeri’ lineage survived effectively on Australian plants but had significantly lower settlement rates, longer duration of development and produced smaller females on the South Africa C. pallida. The ‘pallida’ lineage had similar settlement, mass and fecundity on South African plants when compared to Mexican plants. The results indicate that the ‘californica var. parkeri’ lineage is incompatible with C. pallida plants in South Africa. The ‘pallida’ lineage is compatible with South African C. pallida and should be considered further as a potential agent.