Low-input integrated management of tomato viruses in Hawaii

Low-input integrated management of tomato viruses in Hawaii

Summary

Tomato production in Hawaii has been severely hampered by insect-vectored plant pathogenic viruses for decades. Varieties resistant to the major pathogen, Tomato spotted wilt virus, have been used extensively to deal with this problem, and the industry has grown substantially. The recent advent of Tomato yellow curl virus in Hawaii has set the tomato industry back to depending extensively on insecticides for virus vector management. There are currently no varieties with dual resistance to these viruses available for commercial production in Hawaii. This project will address this problem through screening tomato varieties with putative dual resistance to confirm resistance and to determine their desirability for the local industry. We will also consider integrated management options for virus vector suppression (thrips and whiteflies), including barrier sprays (kaolin), horticultural oils, insect pathogenic fungi and use of reflective mulches to deter the insects. A combination of tolerance or resistance with low-input insect suppression techniques will provide an effective and valuable tool that will enable farmers to continue producing tomatoes in Hawaii.

Objectives/Performance Targets

1. Evaluation of resistant varieties

2. Evaluate effectiveness of kaolin clay, horticultural oil, B. bassiana and reflective plastic mulch to suppress insect vectors

3. Conduct economical analysis of sustainable strategies to control TSWV and TYLCV in tomato in Hawaii

4. Disseminate research findings to tomato growers and agricultural professionals

Accomplishments/Milestones

During 2013, two field trials were carried out in two locations on the island of Oahu to test commercially available tomato varieties resistant  to two viruses: Tomato Yellow Leaf Curl (TYLCV – transmitted by whiteflies) and Tomato Spotted Wilt Virus (TWSV). The trials also included susceptible varieties to be able to assess the difference. The first trial tested 10 tomato varieties (Table 1) and was done in Waimanalo from April to August 2013. The second trial tested 15 tomato varieties (Table 2) and was done in Waialua from July to November 2013. In both trials insect vector density data was collected for eight weeks starting from the second week after transplanting. Bemisia  argentifolii nymph densities (vector of TYLCV) were assessed by collecting three terminal leaflets from the seventh node down from the terminal growing point of the plant. Thrips species, Thrips tabaci and Frankliniella schultzei, densities (vectors of TSWV) were assessed by collecting two flowers per three randomly selected plants within each variety, per replicate. Flowers were dissected and thrips were counted using a dissecting microscope. DAS-ELISA was used to confirm TYLCV and TSWV infection at the midpoint of the trial. For both trials yield data was taken for four to six weeks.

• Figures and tables pertaining to Wright et al, low-input integrated management of tomato viruses in Hawaii

Impacts and Contributions/Outcomes

Many of the varieties tested during 2013 proved to be resistant to one or both viruses when grown side by side with susceptible varieties. At the end of the Waialua field trial, a field day was hosted for farmers and agricultural professionals to give them an opportunity to observe the varieties in the field and to taste the tomatoes. Taste tests were done at the field day and at the university campus to assess the acceptance of the different varieties (results are still being analyzed).

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