Oecophylla smaragdinaants provide pest control in Australian cacao

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AbstractEcosystem service‐driven methods of agricultural production that make optimal use of an ecosystem's natural services are often effective in smallholder crops, leading increases in habitat heterogeneity at large spatial scales that encourage beneficial species. Pollination services in cacao farms can be enhanced through efforts to conserve pollinator habitats, such as adding cacao fruit husks underneath trees to provide habitat and food resources for midge pollinators. However, it remains unclear how this habitat manipulation affects pest densities or biological control. Here, we evaluated the effects of the predaceous antOecophylla smaragdinaon three major pests of Australian cacao (Helopeltisspp.,Amblypeltaspp., andRhyparida nitida) in an Australian cacao farm, in the presence and absence of cacao fruit husks. We also evaluated the effect ofO. smaragdinaon their potentially plant‐damaging, mutualistic mealybug (Pseudococcidae) partners in the presence and absence of cacao fruit husks.Oecophylla smaragdinareduced the combined densities ofHelopeltisspp. andAmblypeltaspp., regardless of cacao fruit husk addition. The ants also reduced the densities ofR. nitidain the absence of cacao fruit husks, butR. nitidadensities were naturally low in the experimental plots that received the addition of cacao fruit husks, regardless of ant presence. In contrast, ants generally increased the densities of mealybugs. These data suggest thatO. smaragdinaants provide pest control services for three major insect pests in Australian cacao farms. Furthermore, this control may be compatible with habitat manipulations (i.e., the addition of cacao fruit husks) to improve pollinator habitat.