Assessment of the Positive and Negative Effects of Earwigs in Apple Orchards

Project Overview

Project Type: Graduate Student
Funds awarded in 2018: $17,875.00
Projected End Date: 07/31/2018
Grant Recipient: Washington State University
Region: Western
State: Washington
Graduate Student:
Principal Investigator:
Dr. David Crowder
Washington State University


  • Fruits: apples


  • Education and Training: extension
  • Pest Management: biological control, field monitoring/scouting, integrated pest management

    Proposal abstract:

    Biological control (pest suppression by predators and parasitoids) is a critical component of integrated pest management (IPM) for apple pests. Biological control is particularly crucial for management of the woolly apple aphids (Eriosoma lanigerum), because they are difficult to manage with currently available insecticides. We interviewed apple orchard managers about the effectiveness of different predators for suppressing woolly apple aphids, and they clearly considered the European earwig (Forficula auricularia) as the least valuable. In contrast, many studies suggest earwigs are a key predator of woolly apple aphids. Apple orchard managers sometimes expressed concerns that earwigs directly damage apple fruits, but in fact, it is not clear whether earwigs cause damage or merely seek shelter in existing wounds. Given that earwigs are very common in apple orchards ,there is a need to assess whether earwigs in apple orchards are a pest, a beneficial, or both.

    We propose to quantify positive effects (aphid suppression) and negative effects (fruit damage) of earwigs in commercial apple orchards, and compare the perceptions of interviewed managers with our field data. We will accomplish this by (1) manipulation of earwig densities in commercial orchards, (2) molecular analysis of earwig stomach contents, and (3) in-depth interviews with apple orchard managers. Based on literature and our preliminary data, we hypothesize that earwigs suppress woolly apple aphids and do not initiate damage to apple fruit. The goal of our outreach program will be to use presentations, publications, and mass media to alert apple orchard managers to the effects of earwigs, and to recommend appropriate tactics to harness their benefits. This research and outreach will provide information to prevent unnecessary sprays targeted against earwigs and to improve woolly apple aphid management. Our project therefore meets SARE goals of promoting agricultural sustainability while minimizing impacts on the environment.

    Project objectives from proposal:

    Objective 1.  Test for positive and negative effects of earwigs in apple orchards

    Sub-objective 1a: manipulate and monitor earwig densities within4 apple orchards

    Sub-objective 1b: count the number of woolly apple aphid, rosy apple aphid, and green apple aphid colonies in the study sections (May to October 2017)

    Sub-objective 1c: quantify and characterize fruit damage in the study sections

    Objective 2.  Assess what earwigs fed upon in the 4 apple orchards by molecular analysis of gut contents

    Sub-objective 2a: collect samples of 20 earwigs from at least 6time points from a non-manipulated control section of each site

    Sub-objective 2b: Dissect stomachs of all earwigs and test each for presence of woolly apple aphid DNA

    Sub-objective 2c: Broadly characterize the diet of earwigs using next generation sequencing of DNA found in their stomachs

    Objective 3. Learn apple orchardist perceptions of earwigs through in-depth interviews

    Sub-objective 3a: conduct recorded interviews at least 20 apple industry professionals involved in pest management decisions (e.g., owners, managers, consultants)

    Sub-objective 3b: transcribe interviews to text and analyze responses

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.