Floral resources and ground covers can reduce pesticide use while maintaining fruit quality in apple orchards

During the past decades, agricultural intensification and the simplification of agroecosystems have crucially contributed to biodiversity loss. Moreover, decimating farmland biodiversity threatens associated ecosystem services such as the control of pest insects by natural enemies. This is also true for apples, one of the most intensively produced fruit crops in the world. Facing the growing demand and the high-quality standards (e.g., immaculate fruits, free from pesticide residues) of the market while at the same time minimising negative environmental impacts, producers need more ecological-friendly strategies.

Conservation biological control (CBC) is considered such a strategy. It attempts to counteract habitat loss and disturbance associated with intensive crop production by diversifying habitats or by reducing the management intensity to conserve natural enemies and thereby contribute to pest control. However, it is a complex strategy, encompassing various measures, and effects are inconsistent.

Researchers from the University of Natural Resources and Life Sciences (BOKU), Austria, and the Centre for Ecological Research, Hungary, found positive results by investigating the effects of environmental-friendly production strategies on the abundance of pest insects and their natural enemies, biocontrol and fruit quality in apple orchards. Their findings were published in the international journal Science of the Total Environment. To shed light on the effectiveness of CBC in apple orchards, the researchers investigated data from 54 studies worldwide. They identified the introduction of flowering components, (aromatic) ground covers and a general extensification in orchard management as the most common measures.

Ground covers increased natural enemies most and had especially positive effects on predators. At the same time, they showed the potential to decrease the abundance of pest insects. Several mechanisms might be involved, and especially aromatic plants seem to have repellent effects on pest insects. They repel them away from the host plant or attract natural enemies, thereby reducing the number of harmful herbivores. Similarly, flowering components increased the abundance of natural enemies, especially parasitoids, which might be attributed to the provision of alternative food sources such as pollen and nectar. In contrast, the extensification of apple orchard management showed no significant effects on the abundance of pest insects or their natural enemies. Extensification was also the only measure that resulted in a reduction in fruit quality.

Christine Judt, the first author of the paper, concludes that “More floral resources and ground covers are feasible alternatives to reduce pesticide use in apple orchards while maintaining fruit quality”. “Promoting these concepts and being applied to other annual and perennial cropping systems to achieve the upcoming policy goals, such as halting biodiversity loss along with a radical reduction of pesticide use, is a vital step towards environmental sustainability – adds Péter Batáry, a co-author of the paper.