Screening tomato varieties for suitability on Guam in response to the arrival of Tomato leaf curl Guam virus in the Western Region

Project Overview

Project Type: Professional + Producer
Funds awarded in 2014: $49,500.00
Projected End Date: 08/31/2017
Grant Recipient: University of Guam
Region: Western
State: Guam
Principal Investigator:
Dr. Robert Schlub
University of Guam

Annual Reports

Information Products


  • Vegetables: tomatoes


  • Crop Production: tissue analysis
  • Education and Training: extension, farmer to farmer, focus group, on-farm/ranch research, participatory research, workshop
  • Pest Management: disease vectors, field monitoring/scouting
  • Production Systems: general crop production


    The project “Screening tomato varieties for suitability on Guam in response to the arrival of Tomato leaf curl Guam virus in the Western Region” was completed over a three-year performance period and a no-cost extension period. This project centered on reducing the impact of this virus on Guam through the introduction of resistant tomato varieties among growers, the elimination of chemicals by farmers to control the disease through controlling whitefly population, and finally the return of the economic vitality of growing tomatoes on Guam.

    The need for this project arose after tomato growers in northern Guam began abandoning production due to yield losses attributed to Tomato leaf curl virus. An island wide survey conducted in July 2013 confirmed the presence of the virus in half of Guam’s farming areas and validated that the virus was in fact responsible for the losses reported earlier by farmers. The research approach used in this project was one of farmer engagement; thereby, giving some growers an incentive to continue producing tomatoes even though Guam’s preferred tomato variety was suffering yield losses.  

    In the first year of the project the groundwork was put into place, meanwhile the virus was confirmed to be a strain of Ageratum yellow vein virus (AYVV) unique to Guam rather than Tomato leaf curl Guam virus (TLCGV). The 5 participating producers were trained and educated on recognition of virus symptoms and on how the variety trial would be conducted. Producers reviewed the characteristics of 40 varieties, prepared by the project graduate student and PI, and then selected 17 varieties for inclusion in the variety trial. The wet season trial was completed in December 2014, at which time the 5 participating farmers visited each test plot and selected the top varieties. Results from the wet season varietal trial were presented in a poster at the 8th International IPM Symposium on March 2015, and included in the 2016 revision of the “Eggplant, Pepper and Tomato Production Guide for Guam.”  

    In the second year of the project the dry season variety trial was planted, unfortunately it was discontinued after the passing of Typhoon Dolphin. In its place another variety trial was conducted, this time using the top 5 varieties identified by the farmers at the end of the dry season. A producer and professional field day was held on October 21, 2015 where participants examined plots and provided variety recommendations. The project was highlighted in the 2015 annual impact report for the College of Natural and Applied Sciences.

    In the third year, a workshop was held for 55 farmers and home gardeners at the University of Guam where the results of this project’s tomato virus resistance variety trial were presented. In an attempt to unravel the cause of tomato leaf purpling, symptomatic leaf samples were sent off-island for DNA analysis; it was determined that Guam’s tomato crops are suffering from a complex of virus diseases and a bacterial disease. An Ageratum yellow vein virus brochure was distributed at meetings of the Guam’s Farmer Cooperative Association, and Guam’s Northern and Southern Conservation Districts.

    The project’s no-cost extension period allowed for the completion of several items: the tomato virus YouTube video; the inclusion of the list of known tomato virus on a 2017 APS Caribbean Division poster, “Plant Diseases of the Western Pacific Tropical Island of Guam”; the presentation of the poster, “Survey and Identification of Viruses Infecting Tomato Crop on Guam” at the 2017 annual meeting of the American Phytopathological Society in 2017 in San Antonio, Texas; and the completing of the project’s final report.

    Project objectives:

    The goal of this project was to return tomato production on Guam to the levels preceding the impact of AYVV (formerly identified as TLCGV). With the completion of our project, tomato grower profitability will improve as growers adopt the recommendations covered in the workshop and the 2016 updated “Eggplant, Pepper and Tomato Production Guide for Guam.”  

    Over the course of this project, three specific and measureable objectives were completed.

    Objective 1 (Year 1): Improve the ability of producers to screen tomato varieties for Tomato leaf curl Guam virus (TLCGV) resistance and suitability for production on Guam.

    Activities for Objective 1: (1) After consulting with project statistician, PI met with producers and provided instruction on virus identification and scoring tomato varieties for resistance to AYVV and suitability for production on Guam. (2) Producers were given pre- and post-tests to measure knowledge gained. (3) Producers reviewed the characteristics of 40 varieties prepared by the project graduate student and PI and selected the 18 varieties that would be included in the trial. (4) PI and graduate student assisted each producer with a wet season variety screening trial. (5) Producers hosted a producer field day and members reevaluated the plots. (6) Producers begin a dry season variety trial but it was terminated due to damage from Typhoon Dolphin. As a replacement, a smaller trial consisting of the local preferred susceptible variety Season Red and 5 resistant varieties were planted. (7) Producers hosted a 2nd producer field day and members evaluated the plots. (8) Project statistician ran a MANOVA of the response variable data on some of the dry season trial data and interpreted the screening trial results for PI and producers.

    Objective 2 (Year 2): Bring awareness to producers and the public about Guam’s whitefly transmitted tomato virus and steps that can be followed to reduce its impact.

    Activities for Objective 2: (9) PI and producers hosted a workshop onsite at one of the variety trial locations for the island’s farmers, home gardeners, NRCS and the Department of Agriculture. After the workshop, an outreach survey was conducted similar to the one posted on the SARE program website. (10) Information presented in the public workshop was included in the 2016 revision of the “Eggplant, Pepper and Tomato Production Guide for Guam” and in a brochure on AYVV produced by the project graduate student. (11) A YouTube video was created about AYVV.

    Objective 3 (Year 3): Bring about the adoption of farm practices that will reduce the occurrence of TLCGV in tomato fields and result in produce production returning to pre-Tomato leaf curl Guam virus levels.

    Activities for Objective 3: (12) The project’s graduate student distributed AYVV brochures at meetings of the Guam’s Farmer Cooperative Association and Guam’s Northern and Southern Conservation Districts. (13) Impact of the project on tomato producers.

    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.