Habitat heterogeneity reduces abundance of invasive mealybugs in subtropical fruit crops

Abstract

Abstract The simplification of agricultural landscapes has been associated with an increase in pest pressure. While monocultures increase the resources available for pests and may facilitate their dispersion, the lack of non‐crop habitats may reduce the resources available for pest natural enemies. Herein, we tested which of these hypotheses, namely ‘resource concentration’ and ‘natural enemies’, can better explain the abundance of invasive mealybug pests in two subtropical fruit crops. For this aim, 17 persimmon orchards and 16 citrus orchards were sampled during three different seasons across two consecutive years. Using a model selection approach, we assessed the effects of the surrounding landscape (proportion of focal crops and semi‐natural habitats at different distances) and inter‐row ground cover vegetation on the abundance of mealybugs and their natural enemies. The proportion of focal crop in the landscape increased the abundance of mealybugs attacking both crops. This effect was found at closer distances (up to ~600 m) in citrus and at both closer and further distances (up to 1250 m) in persimmon. Non‐crop habitats, both surrounding semi‐natural habitats and ground cover vegetation, decreased the abundance of mealybugs by increasing the activity of their parasitoids in persimmon. Conversely, non‐crop habitats did not decrease the abundance of the main mealybug species attacking citrus, likely because this mealybug species was not attacked by native or naturalized parasitoids. Synthesis and applications. Our models show that the increase in habitat heterogeneity at local and landscape scales can reduce the abundance of invasive mealybugs in subtropical crops via ‘resource concentration’ and ‘natural enemies’ mechanisms. Therefore, habitat diversification strategies should be considered in the conservation biological control of invasive mealybugs. Importantly, our findings also show that the presence of efficient natural enemies is critical to maximize their control through habitat diversification strategies.