Cultural Management of Onion Thrips and Iris yellow Spot Virus

Project Overview

Project Type: Research and Education
Funds awarded in 2008: $133,441.00
Projected End Date: 12/31/2011
Region: Western
State: Utah
Principal Investigator:
Dr. Jennifer Reeve
Utah State University

Annual Reports


  • Agronomic: corn, wheat
  • Vegetables: carrots, onions


  • Crop Production: intercropping, application rate management
  • Education and Training: extension, on-farm/ranch research
  • Farm Business Management: budgets/cost and returns
  • Pest Management: cultural control, disease vectors, trap crops
  • Production Systems: agroecosystems
  • Soil Management: nutrient mineralization


    Our farm survey showed no correlation between input intensity and yield or onion size. Thrips incidence was greater in fields fertilized with higher nitrogen (N). Moreover, considerable N was present in the soil at harvest. The impact of higher N on thrips and N leaching was confirmed in replicated trials. Yields and onion size were similar between higher and lower N rates when onions were planted in a timely manner. Thrips populations were lower on onions planted after corn than after wheat, and we saw no effect of a soil biostimulant. Lacy phacelia and buckwheat show potential as trap crops, although synchronization of trap crop blooming period with peak thrips densities may be critical.

    Project objectives:

    In order to meet the multiple goals of increased environmental and economic sustainability, enhanced quality of life and worker safety, and increased farmland diversification in onion cropping systems, we studied the following six objectives:

    1) work with local growers to determine onion thrips and IYSV pressure in primary Utah onion growing areas and correlate thrips and IYSV pressure to common farm practices;

    2) determine the effects of crop and pest management strategies on thrips survival and population size;

    3) evaluate nitrogen (N) inputs, N leaching potential, alternative fertilizers, trap crops and crop rotation on thrips, IYSV, onion yields and storage quality;

    4) conduct grower workshops and field days on control options of onion thrips and IYSV;

    5) conduct economic cost-benefit analysis of proposed changes to management of onion thrips and IYSV; and

    6) disseminate results through extension bulletins, the Internet, trade journals and scientific literature.

    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.