Cover crops to enhance control of leaffooted bug, Leptoglossus zonatus, in California tree nut crops

Project Overview

Project Type: Graduate Student
Funds awarded in 2020: $24,796.00
Projected End Date: 07/31/2022
Host Institution Award ID: G150-21-W7902
Grant Recipient: University of California, Riverside
Region: Western
State: California
Graduate Student:
Principal Investigator:
Dr. Houston Wilson
University of California, Riverside
Principal Investigator:
Dr. Kent Daane
University of California, Berkeley


  • Nuts: pistachios


  • Crop Production: alley cropping, cover crops
  • Education and Training: on-farm/ranch research
  • Farm Business Management: budgets/cost and returns
  • Natural Resources/Environment: biodiversity, habitat enhancement, strip cropping
  • Pest Management: biological control, chemical control, cultural control, economic threshold, field monitoring/scouting, integrated pest management, row covers (for pests), trap crops
  • Production Systems: agroecosystems
  • Sustainable Communities: sustainability measures

    Proposal abstract:

    Leaffooted bugs are significant pests of tree nut crops in California. In almond and pistachio, feeding damage can lead to epicarp lesions, kernel necrosis and stigmatomycosis. Given the pest’s rapid and unpredictable colonization into orchards, and lack of effective monitoring tools to detect such migrations, growers rely extensively on pesticides to control these insects, commonly at first perceived risk of pest activity. This management approach is both economically costly and environmentally unsustainable. In 2018-19, our group initiated a collaborative project with a large nut producer to explore the use of summer cover crops as an integrated pest management (IPM) strategy for large hemipteran pests. Here, we assessed the influence novel, irrigated strips of ground cover in both reducing pest damage and increasing biological control of leaffooted bug. Building from preliminary findings, ground covers will be selected that are attractive to leaffooted bugs, but also provide nectar resources for its primary parasitoid, Gryon pennsylvanicum. In this way, covers may provide multiple services, including (1) act as a trap crop to hold leaffooted bug away from the crop canopy, and (2) provide flowering resources for key natural enemies of these pests. Partnering with UC Cooperative Extension and collaborating producers, our finding will be disseminated to relevant stakeholders, producers, and the academic community to address a growing need in California tree nut IPM. Improved methods in leaffooted bug management will reduce pesticide application costs, as well as environmental costs derived from the overuse of insecticides in California tree nut crops.

    Project objectives from proposal:

    Objective 1: Quantify leaffooted bug attraction to candidate trap crop species.

    Evaluating leaffooted bug attraction to selected ground cover plants (e.g. mustard, vetch, clover, buckwheat, and garbanzo bean) will provide a targeted and measurable assessment to the efficacy of trap plants in controlled conditions. We will use these results to evaluate findings under field conditions, as well as provide insight to alternative trap plants.


    Objective 2: Measure the impact of trap crop plants on life parameters of leaffooted bug parasitoid Gryon pennsylvanicum.

    Understanding the influence nectar provisions from candidate trap plants have on G. pennsylvanicum life parameters will provide insight to the role ground covers have on this key natural enemy. Influence of nectar feeding from trap plants will be compared to optimal sugar diets.


    Objective 3: Evaluate the influence of ground covers on biological control of leaffooted bug and crop damage.


    (3A) Monitor seasonal abundance of leaffooted bug and their key natural enemies in nut orchards with and without trap crops.

    Assessing the spatiotemporal abundance of leaffooted bugs and their natural enemies in plots with and without trap crops will provide insight to the efficacy of trap cropping for (1) luring and holding the pest away from the canopy and (2) supporting natural enemy populations.


    (3B) Assess parasitism of leaffooted bug in plots with and without trap crops.

    Using sentinel egg masses, we will measure parasitism and predation rates in the presence and absence of ground covers. Natural enemy abundance measured in 3A will be compared to the degree of biocontrol observed in plots.


    (3C) Determine whether trap crops reduce crop damage.

    Quantifying insect damage provides the ultimate measure of whether trap cropping can be a viable pest management tool in nut crops. We will compare leaffooted bug feeding damage to nuts in plots with and without trap crops.

    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.