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

    Proposal abstract:

    Tomato growers in northern Guam are being forced to abandon production due to the impact of the Tomato leaf curl virus. This project will screen tomato varieties for suitability on Guam and inform growers and the public about the virus and steps they can take to reduce the impact of the Tomato leaf curl disease. A similar approach proved successful for Hawaii growers when an emerging disease caused by a related Tomato yellow leaf curl virus (TYLCV) appeared in Hawaii in 2009. In the spring of 2011, severe leaf curling and stunting of tomato plants - Season Red variety - were observed in farms in the villages of Yigo and Dededo on Guam. At the time, it was only diagnosed as a virus disease. After considerable work on the virus’s genome sequence, Dr. Kai-Shu Ling of the USDA- ARS, U.S. Vegetable Laboratory in Charleston, South Carolina determined that Guam had a novel form of the whitefly-transmitted tomato leaf curl virus and developed, for the first time, a sensitive and specific molecular method for its detection. Because this virus is known to cause heavy losses and was not yet in the contiguous 48 states, Dr. Ling decided further research was warranted. In June 2012, he recommended, and Dr. Robert Schlub concurred, that the virus should be named Tomato Leaf Curl Guam Virus (TLCGV). An island wide survey conducted in July 2013 confirmed the virus is present in half of Guam’s farming areas and is virulent enough to cause farmers to cut back their tomato production or to abandon it altogether. For the past two decades, tomatoes have held the distinction of being the third most popular commercially grown crop on Guam. Of the roughly two dozen varieties of tomato that have been grown over this time, the determinate cherry tomato, Season Red, has emerged as the top choice among growers. No other tomato can beat its vigorous growth and tolerance to heat and humidity, while only costing $0.02 per seed. The legacy of the tomato's being a sustainable commercial crop for Guam may soon be over. The average farm on Guam is less than two acres in size, operates at a subsistence level, produces $21,000 worth of produce, and is largely dependent on family members as laborers. Farmers are willing to support research and education by supplying land and basic infrastructure but cannot afford to sacrifice produce. This project approaches Guam’s tomato virus disease problem in a unique and resourceful manner in order to keep growers from abandoning production before solutions can be developed. This project willto screen 18 varieties for virus resistance and suitability for production on five farms from a preselected list of 40 candidates generated by the PI and project graduate student. Only commercially available varieties which have promise of resistance to TLCV and suitability to Guam’s environment will be included in the final 18 varieties for field screening. The produce will be the property of the producers to offset their costs. The experimental design, data collection and analysis will be under the direction of a statistician, thereby insuring the results will be suitable for publication in a refereed journal. The educational plan will consist of educating producers and the public about Guam’s whitefly transmitted TLCGV and its associated disease. Producers will learn how to set up a virus screening trial, how to recognize symptomatic plants, and how to collect and record data. After the screening trial, a workshop will be held for tomato producers and the public concerning TLCGV and common IPM practices that can be used to reduce its impact. During the workshop, participating project producers will present their findings. Information from the workshop will be placed in a brochure and posted on the UOG/ANR webpage. A YouTube video will be created about TLCGV using the information in the brochure.

    Project objectives from proposal:

    This project has three specific and measureable objectives which will be achieved over a three-year period. These objectives will be the end result of various activities scheduled through the course of the project.


    Objective 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) June 2014, after consulting with project statistician, PI will meet with producers and instruct them on virus identification and score tomato varieties for resistance to TLCGV and suitablity for production on Guam. (2) Producers will be given pre- and post-tests to measure knowledge gained. (3) Producers will review the characteristics of 40 varieties prepared by the project graduate student and PI and select the 18 varieties that will be included trial. (4) August 2014, PI and graduate student will assist each producer with a wet season varietal screening trial. (5) October 2014, producers will host a producer field day and members will reevaluate plots. Rating will continue until December 2014. (6) March 2015, producers begin dry season varietal trial. (7) May 2015, producers will host a producer field day and members will reevaluate plots. Plot will continue until July 2015. (8) October 2015, project statistician will run a MANOVA of the response variable data and interpret screening trial results for PI and producers.


    Objective 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) December 2015, PI and producer will host a workshop onsite at one of the variety trial locations for the islands farmers, home gardeners, NRCS and the Department of Agriculture. After the workshop, an outreach survey will be conducted similar in design and purpose to the one posted on the SARE program website. (10) January 2016, Information from the workshop will be placed in a brochure and posted on the UOG/ANR webpage. (11) March 2016, a YouTube video will be created about TLCGV using information in the brochure.


    Objective 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) May 2016, Graduate student will distribute TLCGV brochures at meetings of the Guam’s Farmer Cooperative Association and Guam’s Northern and Southern Conservation Districts. (13) December 2016, a long-term outreach survey will be created to assess changes in farmer attitude and adoption of control strategies. The project statistician will assist in questionnaire development and interpretations. (14) February 2017, PI, graduate student and statistician will prepare and submit final project report.

    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.