Floral resources and ground covers promote natural enemies but not pest insects in apple orchards: A global meta-analysis.

In recent decades, agricultural intensification has led to a loss of biodiversity and associated ecosystem services such as natural pest control. Conservation biological control addresses this problem by generally extensifying farming and/or providing alternative habitats and food sources for natural enemies of pest species. However, farmers implement conservation biological control sparingly, in part because of the confusing variety of measures with inconsistent effects. To shed some light on the effectiveness of conservation biological control measures in apple production, we conducted four meta-analyses to identify patterns of local measures on (i) insect pest abundance, (ii) natural enemy abundance, (iii) biological control, and (iv) fruit quality. Across the 54 studies, we found an overall significant, positive effect of local interventions on natural enemy abundance. Among our established intervention categories (flowers, ground cover, extensification), ground covers promoted natural enemies the most and tended to reduce pest insects. Likewise, providing flowers promoted natural enemies without affecting fruit quality. In contrast, extensification of orchard management alone, such as reducing agrochemical use and/or less disturbance, had no significant effect on the abundance of natural enemies, but showed a tendency to increase populations of pest insects and reduce fruit quality. Our results demonstrate that more floral resources and ground covers in apple orchards can reduce pesticide use while maintaining fruit quality.

Diverging Effects of Landscape Factors and Inter-Row Management on the Abundance of Beneficial and Herbivorous Arthropods in Andalusian Vineyards (Spain).

Land use at landscape and field scales can increase the diversity and abundance of natural enemies for pest control. In this study, we investigated interactions between landscape elements (semi-natural vegetation, olive orchards, vineyards, other agricultural areas) and inter-row management (vegetation cover vs. bare soil) in relation to arthropod populations in Andalusian vineyards. Arthropods were collected from grapevine foliage in 15 vineyards using suction sampling. Landscape structure was analyzed within a 750 m radius surrounding the studied vineyards. Arthropods were categorized into functional groups (predators, parasitoids, herbivores), and their responses to the most influencing factors were analyzed by likelihood methods and model selection. Of the total of 650 arthropods collected, 48% were predators, 33% herbivores and 19% parasitoids. Numbers of predatory aeolothrips, parasitoids and herbivorous cicadas in the study vineyards decreased with an increased proportion of vineyards in the surroundings. Spider populations in vineyards increased with increasing proportions of other agricultural fields (non-flowering crops) in the surroundings. Semi-natural elements and olive orchards had no influence on the abundance of collected arthropods. We observed synergistic effects between landscape elements and inter-row management. The total numbers of arthropods, herbivores and parasitoids in vineyards benefitted from inter-row vegetation, while spiders benefitted from bare soil. Our findings underline the importance of both surrounding landscape elements and vineyard ground cover management to promote beneficial arthropods for potential natural pest control.