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

Abstract

Fruit-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 39 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.

Variability of Gut Microbiota Across the Life Cycle of Grapholita molesta (Lepidoptera: Tortricidae)

“…In China, it occurs in most of the fruit-growing regions except Tibet and can harm apple, pear, jujube, peach, plum, apricot, hawthorn, and other fruit trees by boring and feeding in twigs and fruits at larval stage, resulting in shoot dieback and fruit shedding ( Myers et al, 2006 ; Cao et al, 2015 ; Duarte et al, 2015 ; Tian et al, 2019 ). G. molesta undergoes multiple generations in a year and has the habit of host switching, which cause serious economic losses to the fruit industry every year ( Zheng et al, 2015 ). Intensive use of insecticides in orchard poses risks to fruit quality and environmental contamination and selection pressure on the oriental fruit moth to evolve resistance.…”

Integrated management of tortricid pests of tree fruit

“…Two additional physical methods have been considered and used on a limited basis to manage tortricids: bagging individual fruits on trees (Sharma et al 2014;Zheng et al 2015) and the use of overhead watering to disrupt moth flight, oviposition, and egg and larval survivorship (Knight 1998b). Bagging is obviously a highly labour-intensive method and likely has no practical use in commercial fruit production in developed countries, except very niche markets, that is special gifts in Japan.…”

Diversity of tortricid moths in apple orchards: evidence for a cryptic species ofGrapholita(Lepidoptera: Tortricidae) from China

“…After verification via gel electrophoresis, the PCR products were purified with a Wizard PCR Preps kit (Promega, Madison, WI, USA), and then sequenced in both directions with the PCR amplification primers on an ABI3730XL DNA analyzer (Applied Biosystems, Foster City, CA, USA) using the commercial services of Sangon Biotech (Shanghai, China). For genetic diversity analyses, a 740 bp mitochondrial cytochrome oxidase subunit I (COI) sequence and a 683 bp cytochrome oxidase subunit II (COII) sequence, which were applied to analyze genetic diversity of G. molesta (Zheng et al, 2013;Zheng et al, 2015), were adopted in the current study. The COI sequence of the second species was amplified with the primer pairs C1-J-2183 (5′-CAACATTTATTT TGATTTTTTGG-3′) and TL2-N-3014 (5′-TCCAATGCAC TAATCTGCCATATTA-3′) (Simon et al, 1994), while the COII sequence was amplified using the primer pairs TL2-J-3037 (5′-ATGGCAGATTATATGTAATGG-3′) and TK-N-3785 (5′-GTTTAAGAGACCAGTACTTG-3′) (Simon et al, 1994).…”

“…The oriental fruit moth occurs on several pome and stone fruit species (Rothschild & Vickers, 1991;Natale et al, 2003;Najar-Rodriguez et al, 2013), and to exclude effects of different host plants on herbivore diversity (Zheng et al, 2013), we focus here on apple, which is rapidly gaining importance in China (http://faostat3.fao.org/download/Q/QC/E). For field trapping of G. molesta, we used the commercially available pheromone trap developed for monitoring, which proved to be highly selective for this tortricid in previous work in other regions of China (Li et al, 2008;Wang et al, 2013;Zheng et al, 2015).…”