Effects of hedgerow characteristics on intra-orchard distribution of larval codling moth

The spatial distribution of diapausing larvae of codling moth (Cydia pomonella), a common pest species, was analysed in several commercial orchards during 3 consecutive years. Extent and location of the clustering of diapausing larval codling moth were first assessed in each orchard. The between year differences in clustering patterns were then checked. The relation of clustering patterns to characteristics of neighbouring hedgerow was finally tested. Clustering was detected in 16 orchards out of 53 (30.2%) in 2006, in 10 orchards out of 50 (20%) in 2007, and in 13 orchards out of 40 (32.5%) in 2008. The clustering pattern was generally similar between years. There was a consistent influence of neighbouring hedgerows on the spatial distribution of individuals. The number of larvae was lower – depending on the year – in areas either closest to hedgerows or under the influence of hedgerow shadow or wind protection depending on the year. Further, in one of the years, the number of larvae was negatively correlated with the floral diversity of the nearby hedgerow. This study suggests that hedgerows influence codling moth population dynamics and may play a key role in reducing the abundance of this species within orchards.

Research highlights▶ Clustering was detected in 20–32% of the orchards and was similar between years. ▶ The density of larvae was consistently lower in areas close to or protected by hedges.