Identification key to scarabaeid larvae attacking sugarcane in South Africa
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Abstract
Scarabaeid pests in South Africa and especially KwaZulu-Natal are characterised by a very long larval life cycle and short pupal and adult periods. However, it has nearly always been the adults of the species that have been identified, with very little attention paid to larval identification. This is unfortunate, as it is mainly the larval stage that is found to be associated with crop damage. Inadequate keys for the taxonomy of larvae of these groups, as well as the lack of taxonomists working on these groups have been identified as constraints. Using mitochondrial DNA data variation in the base pair sequence of the mitochondrial cytochrome c oxidase sub unit I (cox 1) gene, sequences of cox 1 from scarabaeid larvae collected from sugarcane fields were compared with sequences from scarabaeid adults of known species in order to identify the species attacking sugarcane. The major groupings delimited specimens belonging to the subfamilies Dynastinae, Melolonthinae and Rutelinae. Mitochondrial DNA (mtDNA) of larval specimens was linked with mtDNA of identified adult specimens through phylogenetic analysis. This allowed the identification of those larvae through morphological characteristics unique to certain species. Keys were produced during this study which will allow workers to identify larvae, in many cases to species. Obtaining species identifications for larvae will allow the application of species-specific control measures and also will facilitate analysis of interactions among species. These taxonomic advances are a start to the improvement of knowledge of the species composition of scarabaeid larvae in sugarcane fields, thus making management and biological control of these pests a greater possibility.
