Diversity of Lepidoptera associated with macadamia nut damage in South Africa and development of molecular tools to monitor pest populations

Abstract

Lepidopteran pests are of major economic importance to macadamia growers worldwide. In South Africa, four species have been associated with macadamia nut damage. Detailed information regarding species composition of the borer larvae in the nuts and the genetic diversity of these species is not however available. Lepidoptera obtained from nuts from the KwaZulu-Natal, Mpumalanga and Limpopo provinces were identified based on COI sequencing. Thaumatotibia batrachopa represented 95% of the larvae collected in damaged nuts across all growing regions. The population genetic diversity and structure of the dominant species were determined using a 650 bp section of the mtDNA cytochrome oxidase I gene to construct a parsimony network. Rapid diagnostic tools were developed, which included a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay for the identification of all four species and species-specific primers for T. batrachopa and T. leucotreta. Population studies of T. batrachopa showed a dominant COI haplotype present in all growing regions, although several unique haplotypes were also present in each region. Overall, the high haplotype diversity observed in this study is in agreement with that of a native population. The populations between the growing regions are, however, not clearly separated and might reflect recent gene flow.