Population genetics affected by pest management using fruit‐bagging: a case study with Grapholita molesta in China

Abstract

AbstractFruit‐bagging is being used as a pest management tool to control fruit moths on several continents. However, nothing is known about how this physical control method affects population genetics of these moths. Focusing on the oriental fruit moth, Grapholita (= Cydia) molesta (Busck) (Lepidoptera: Tortricidae), we used five polymorphic microsatellite loci and two mitochondrial gene sequences to investigate the genetic diversity and genetic structure of populations from three fruit‐bagged and two unbagged apple orchards in five regions of a major fruit‐growing area of China. We sampled each orchard 3× during the season and found high genetic diversity in the samples of populations collected. Populations from fruit‐bagged and unbagged orchards were genetically significantly differentiated, indicating a clear effect of the pest management method applied. Genetic structures of the populations under a given management regime changed in the course of the season in a characteristic manner, and within the same regime, patterns were always similar at a given sampling time. There was no significant isolation by geographical distance. Population genetics from both orchard types did not resemble one another at the beginning of the season, but they did rather at the end. Potential reasons for this unexpected direction of change in population genetic structure are discussed, and we hypothesize that diapause‐related characteristics may account for the patterns observed. The current study documents that pest management methods applied can have an important impact on the genetic diversity and genetic structure of targeted pest insect populations.