The Use of Straw Mulch to Enhance Predator Populations Along with Biopesticides to Control Onion Thrips in Dry Bulb Onions

Project Overview

Project Type: Research and Education
Funds awarded in 2002: $73,800.00
Projected End Date: 12/31/2004
Matching Non-Federal Funds: $10,750.00
Region: Western
State: Oregon
Principal Investigator:
Lynn Jensen
Oregon State University

Annual Reports


  • Vegetables: onions


  • Education and Training: demonstration, extension, on-farm/ranch research
  • Pest Management: biological control, biorational pesticides, integrated pest management, mulches - killed
  • Production Systems: holistic management


    Wheat straw used as a mulch on top of the onion bed has proved useful in reducing injury to thrips (onion and western flower) when used in conjunction with two “soft” insecticides. The insecticides are spinosad (Success – Dow Agra) and azadirachtin (Ecozin – AMVAC Co., and Aza Direct - Gowan Co). These active ingredients are registered for organic production. Four years of testing have shown this insect control program to be equal to or in most cases superior to conventional thrips treatments. Yield and size have been increased by the use of this program, and storage losses to red onions from thrips scarring is reduced.

    Project objectives:

    Determine the relative effects of straw mulch, Success (spinosad), Ecozin (azadirachtin), and Messinger (harpin protein) on thrips control, predator populations, and on yield and quality. Three years duration.

    Demonstrate the effectiveness of the procedures on a larger scale in grower fields.

    Conduct tours to familiarize and educate growers about the project.

    Educate growers on the advantages of alternative thrips control through presentations and publications.

    Evaluate the financial impact of standard grower practices versus alternative control methods.

    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.