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

Project Overview

GW18-039
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:
Major Professor:
Dr. David Crowder
Washington State University

Commodities

  • Fruits: apples

Practices

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

    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 woolly apple aphids (Eriosoma lanigerum) because they are difficult to manage with currently available insecticides. Previously, 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. 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. In contrast, many studies suggest earwigs are a key predator of woolly apple aphids. Given that earwigs are very common in apple orchards, there is a need to understand whether earwigs in apple orchards are a pest, a beneficial, or both.

    In this project, we quantified the positive (aphid suppression) and negative effects (fruit damage) of earwigs in commercial apple orchards, and compared the perceptions of interviewed managers with our field data. To accomplish this, we (1) manipulated earwig densities in commercial orchards, (2) analyzed earwig diets through molecular analysis of their stomach contents, and (3) conducted new in-depth interviews with apple orchard managers about their perceptions of earwigs. Our results provide clear evidence that earwigs suppressed woolly apple aphid populations without initiating damage to apple fruits. However, in our interviews, earwigs were not generally considered a key biological agent of woolly apple aphid, and several interviewees reported spraying insecticides to eliminate earwigs. Taken together, our results suggest that greater appreciation for earwigs and consideration of their conservation in IPM strategies could improve woolly apple aphid biological control and reduce insecticide use.

    Project objectives:

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

    Sub-objective 1a: manipulate and monitor earwig densities within 4 apple orchards

    Sub-objective 1b: count the number of woolly apple aphid colonies in the study sections

    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 4 time points from a 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 16 apple industry professionals involved in pest management decisions

    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.