Bats are major predators of crop pests worldwide. Our research in collaboration with the South African Macadamia Growers’ Association has shown that the diet of bats roosting or feeding in macadamia orchards in Levubu frequently contain pest green vegetable stinkbugs (Nezara viridula). Stinkbugs cause losses of R50 million annually to the macadamia industry. Almost certainly, bats play an important role in the integrated pest management of stink bug pests in macadamia orchards, but this role can and should be quantified (using economic models based on accurate data on the monetary value of bats in terms of reduced costs of insect damage control) in relation to potential management options (such as bat houses). This is the primary aim of three new projects which have been informed by global research developments and collaboration.
Firstly, a new MSc study at University of Venda in collaboration with the Centre for GeoGenetics at the University of Copenhagen will determine variation in the diet of two bat species (Nycteris thebaica and Mops midas) throughout the year in relation to population estimates of bats and two pest complexes (the Heteroptera “stink bug” and Torticidae moth complexes). It is hoped that this study will lead to a more accurate estimation of the actual biomass of pest stinkbugs consumed by bats.
A second project (PHD student Valerie Linden) planned to start in 2015 aims to exclude insectivorous bats and birds from macadamia trees in order to obtain direct estimates of the overall “avoided costs” value of bats. These data will be used to develop economic models to accurately calculate the economic value of bats to macadamia growers.
A third, recently initiated project will monitor some 72 bat houses of at least four designs in macadamia orchards placed in two macadamia-growing regions of Levubu and Tzaneen. A novel “tower” design will be tested which will hopefully provide bats with adequate thermal insulation.
- Seasonal patterns of habitat use by insectivorous bats in a subtropical African agro-ecosystem dominated by macadamia orchards.
- Bats eat pest green vegetable stink bugs (Nezara viridula): Diet analyses of seven insectivorous species of bats roosting and foraging in macadamia orchards.
- Peter Taylor