Edge effects concentrate Conotrachelus nenuphar (Coleoptera: Curculionidae) oviposition with consequences for larval...

Edge-associated distributions of animals are common in natural and managed landscapes, where habitat contrasts influence species densities, behavior, and population dynamics. In agricultural systems, field edges often concentrate insect pests and their associated damage, yet whether edge aggregation enhances pest performance or creates density-dependent constraints remains unclear. We investigated this relationship in the North American tree fruit pest, plum curculio, Conotrachelus nenuphar (Coleoptera: Curculionidae), by quantifying pest spatial distribution, fruit injury, and reproductive performance in a 4.2-acre peach orchard containing 355 trees (Prunus persica var. "Fantasia"). Between 19 May and 25 August 2025, we measured adult abundance, feeding injury, oviposition scars, larval abundance and emergence, and larval mass across trees and then evaluated density-dependent effects on adult injury behavior using no-choice bioassays. Although adult abundance was evenly distributed throughout the orchard, feeding injury, oviposition scarring, and larval abundance were concentrated along orchard edges. Increased oviposition at edges produced greater larval abundance and density than in interior trees, demonstrating enhanced reproductive output. However, larvae from edge fruit were smaller on average, suggesting density-dependent constraints on offspring development. No-choice bioassays supported these patterns, with doubled adult densities increasing feeding injury by 38%. Edge-associated pest pressure was linked with reduced fruit yield, with damage increasing and yield declining from the orchard interior toward the edge. Together, these findings demonstrate that orchard edges promote pest reproductive output through spatial aggregation while density-dependent constraints emerge at high larval densities.