Bouarakia, Oussama, Linden, Valerie M.G., Joubert, Elsje, Weier, Sina M., Grass, Ingo, Tscharntke, Teja, Foord, Stefan H., and Taylor, Peter J.
The global macadamia industry is growing rapidly, and the world's biggest macadamia nut producer, South Africa, is continuously expanding its production. Insect pest mitigation and research are mainly focused on the damage caused by heteropteran pest species, whereas the damage associated with lepidopteran tortricid moths in South African macadamia orchards is understudied. Here we explore the potential biocontrol of tortricid moths by natural predators through full exclosure of bats and birds, daytime only exclosure (birds), night exclosure (bats and possibly nocturnal birds), and control treatments. The exclusion experiment showed that bats and birds are effective natural predators, which can reduce tortricid moth damage by more than 35%. Impacts of biocontrol are higher at natural orchard edges next to natural or semi-natural vegetation, compared to human-modified edges (12.4% damage decrease in 2017, 10.6% in 2018). At the full exclosure, there was no difference in damage between natural orchard edges and human-modified edges, in both years of our study (56.5% vs. 56.6% in 2017, 19% vs. 18.5% in 2018). We recommend increased preservation efforts of more heterogeneity with semi-natural vegetation in agricultural landscapes to ensure the conservation of biocontrol services, as their loss can be expected to result in significant negative impact on macadamia production. This biological pest control can be used as part of integrated pest management to reduce the reliance on chemical pesticides, so decreasing sustainability challenges. [Display omitted] • Insect pest mitigation and research in South African macadamia have mainly focused on Heteroptera, neglecting Lepidoptera. • We used an exclusion experiment to quantify how biocontrol of Tortricidae varied between bats, birds, and landscape context. • Bats and birds were effective natural predators that reduced tortricid husk damage by more than 35%. • Biocontrol impacts were higher at orchard edges bordering natural vegetation. • Maintaining remnant natural vegetation in agricultural landscapes can reduce crop losses. [ABSTRACT FROM AUTHOR]