Community Structure and Morphospecies Composition of Whitegrubs (Coleoptera: Scarabaeidae) Attacking Plantation Acacia mearnsii Seedlings in KwaZulu-Natal, South Africa

There is a paucity of knowledge of whitegrub pest species in black wattle (Acacia mearnsii) plantations, which hampers the development of integrated pest management programmes. This study determined the composition and community structure of the various whitegrub morphospecies that attacked seedlings during their re-establishment on 10 previous wattle sites in KwaZulu-Natal, South Africa. Whitegrub specimens collected from these trials were examined in the laboratory to determine which morphospecies were present and their abundance. Morphospecies were separated on the basis of their species-specific raster patterns. Multivariate analyses were done using PRIMER (Plymouth Routines in Multivariate Ecological Research) as statistical package. The proportions of morphospecies at the different sites were evaluated by using the non-metric multi-dimensional scaling (MDS). Thirteen whitegrub pest morphospecies were found attacking A. mearnsii seedlings. About 98%of the total whitegrub abundance was represented by seven morphospecies and the remaining about 2%was represented by six whitegrub morphospecies. Three different whitegrub pest community structure patterns were found. The black wattle silvicultural weeding and plantation residue management practices of the South African forestry industry explained the resultant three whitegrub pest community assemblages. These practices were windrowed-burnt-weeded or with closer spacing, weeded fallow sites and windrowed-burnt-ripped or planted in an old arable land. The greatest species richness (13 morphospecies) and abundance (95 %) of whitegrubs was the community assemblage under the windrowed and burnt silvicultural practices. The whitegrub pest community was less abundant (3% and 2%) and diverse (six and five morphospecies) in sites that were left fallow before planting and where the silvicultural practices were windrowing, burning and ripping or planting in an old arable site, respectively.