Evaluating the exclusion and non-target effects of shade netting on apple orchards

Project Overview

Project Type: Graduate Student
Funds awarded in 2017: $23,678.00
Projected End Date: 11/30/2018
Grant Recipient: Washington State University
Region: Western
State: Washington
Graduate Student:
Major Professor:
Dr. Elizabeth Beers
Washington State University


  • Fruits: apples, general tree fruits


  • Pest Management: integrated pest management, physical control


    With apple orchards shifting towards high density production, sunburn has become a major threat to fruit quality and cosmetic appearance. Growers have tried many tactics to reduce sunburn, ranging from sprayed sunscreens to overhead misting systems. Recently, newer orchards are being equipped with shade netting structures which have shown to be the most effective method to reduce direct sunlight. While helping to prevent sun damage, these netting structures could also act as barriers to direct pests such as the codling moth (Cydia pomonella) and brown marmorated stink bug (BMSB) (Halyomorpha halys, Stål). Codling moth have been the primary insect pest of apples for the past century, whereas BMSB recently established in the United States. BMSB is already a signficant pest and has caused catastrophic losses to mid-Atlantic apple growers. Nets may successfully exclude direct pests, but they could also block natural enemies and disrupt biological. We aim to answer these questions with ­­­three main objectives: 1) Determine the effectiveness of different shade net structures in excluding direct pests; 2) Quantify the effects of netting on natural enemies and secondary pests of apple orchards; 3) Inform growers and the public on the role of netting in sustainable orchard systems. To accomplish these objectives we collaborated with five apple orchardists in central Washington and utilized two experimental apple plots provided by the WSU Tree Fruit Research Extension Center. In each research block, scaled-down replicas of commercial netting structures were installed; 16 cages were  built in 2015. In the privately owned plots, barriers at the interface of the natural habitat and the orchard were constructed in 2016. In the research blocks mark and recapture studies using the native stink bug E. conspersus, since BMSB has not established yet, were conducted  to determine the cages exclusion abilities. Coinciding with this were weekly sampling experiments to quantify the netting's effects on resident pests and their natural enemies for the 2016 and 2017 field seasons. Our two year study results show that full enclosure netting significantly reduced direct pest abundance and fruit damage compared to conventional practices. The barriers experiments in the private orchards were conducted for three years (2016, 2017, and 2018) and did not significantly affect stink bug damage, although the barrier reduced the proportion of stink bugs migrating into the orchard. Monitoring the stink bug populations throughout the season gave insight into their biology and behavior, which will be useful to developing future control tactics. Along with these experiments there has been an elaborate outreach program involving cooperation with current researchers, local orchardists, and public organizations. Efforts to date have included six scientific and twelve grower oriented talks, an informational booth at Wenatchee's farmers market, an updated BMSB article on the WSU TFREC website (treefruit.wsu.edu), and distribution of a brochure on BMSB in Washington. To continue we will send updates of our findings to the nationally recognized StopBMSB.org website, and submit our research for publication in entomological journals.

    Project objectives:

    Objective 1: Determine different shade net structures effectiveness at excluding codling moth and stink bugs.

    Objective 2: Examine the effects of shade netting on resident pest and natural enemies in apple orchards.

          (i). Sub-Objective 2a: Monitor resident pest and natural enemy densities inside and outside the cages.

          (ii). Sub-Objective 2b: Measure ambient air temperature and humidity inside and outside the cages.   

    Objective 3: Inform growers and the community of the effects of netting in orchards.

          (i). Sub-Objective 3a: Create online media focused on BMSB and netting implementation in orchards.

          (ii). Sub-Objective 3b: Update the WSU website and StopBMSB.org with our current research and findings.

          (iii). Sub-Objective 3c: Develop and distribute brochures on BMSB and shade netting at the community center and local environmental agencies.  


    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.