Comparing Insect Predation by Birds and Insects in an Apple Orchard and Neighboring Unmanaged Habitat: Implications for Ecosystem Services

SIMPLE SUMMARY: The study aimed to understand the differences in predation of insect pests between managed apple orchards and surrounding habitats. The researchers used mealworm (Tenebrio molitor) pupae as a proxy for coddling moth (Cydia pomonella) pupae and placed them in 42 stations within the orchard and 42 stations in a Eucalyptus stand. Half of the stations were covered with nets to prevent bird predation, while the other half were accessible to birds and insects. The researchers recorded the predation of the pupae and analyzed the videos to determine which species were responsible for the predation. They found that in net-free stations, the predation rate inside the orchard was higher than in the Eucalyptus stand, and the video analysis confirmed that birds were responsible for most of the predation. In netted stations, the predation rate was higher in the Eucalyptus trees, and most of these predations were carried out by ants. The results suggest that the orchard environment negatively affects insect activity as the distance into the orchard increases, specifically predatory ants and that bird predation of insect pests inside the orchard may be more intense than in the surrounding unmanaged habitat. This study highlights the importance of considering the impact of insecticides on the activity of beneficial insect predators in agriculture and suggests that birds may play an important role in controlling insect populations in the orchard. ABSTRACT: Preserving ecosystem services, such as natural enemies that can provide pest control, can positively impact crops without compromising agricultural yield. Even though controlling pests by natural enemies has been suggested to reduce pests in agriculture, growers continue using conventional pesticides that kill beneficial predators. Here we studied whether the predation of avian and insect-beneficial predators varies in an apple orchard with conventional insecticide use compared to a bordering tree stand without insecticides. We studied the predation rates of mealworm pupae as a proxy to coddling moth pupae at 42 stations in both an apple orchard and a Eucalyptus stand at three distances (0 m, 50 m, and 100 m) from the border. Half of the stations were netted to prevent bird predation but were accessible to insects. The other half were non-netted and accessible to birds. We conducted six trials, each lasting two weeks, during which we recorded the predation of 504 stations with 5040 pupae. To validate which species predated the pupae, we added video cameras that took RGB videos during the day and IR videos at night in 45 stations and found that in net-free stations, birds preyed in 94.1% of stations in the orchard and 81.8% in the Eucalyptus stand. However, ants predated 70% of the pupae in stations with nets in the orchards and 100% in stations in the Eucalyptus strands. In addition, we found a significant rise in predation by birds as the distance into the orchard increased. Conversely, insect predation declined within the orchard but escalated in the adjacent unmanaged area. These findings suggest that the orchard’s environment negatively affects beneficial insect activity, specifically predatory ants. This study demonstrates that birds can play an essential role in predating insect pests inside the orchard. In addition, we believe that the decreased predation of ants within the orchard was due to intense insecticide use.