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 addresses 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, Beauveria bassiana, and reflective plastic mulch to suppress insect vector.
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

Two open field trials were conducted in Waialua and Kahuku at Twin Bridge and Ho Farms, respectively. The Waialua field trial was conducted from 06/25/13-11/05/13 and the Kahuku field trial from 01/30/14-07/30/14. Fifteen commercially available tomato varieties (Table 1) were chosen for their individual or dual resistance to TSWV and TYLCV, along with a susceptible control. The trials tested five different types of tomato variety types and two different growth forms (Table 1). Field trials were arranged in a completely randomized design, five replicates per variety and seven plants per replicate.

During the harvest period, fruits were collected weekly from all replications, sorted, and weighed to assess yield productivity of each variety.  In both trials, smaller tomato varieties flowered two weeks before bigger tomato varieties, and thus, fruit production and harvest occurred earlier. Harvest started at different times, but all varieties generally had a three – five weeks harvest period that varied from field trials due to seasonal differences.

Fruits were sorted into six different categories: Marketable, Damaged/Injured, Mite, Splotchy, Fruit Fly, and Hemiptera yield. Fruits were sorted by these six categories, since these were the most common traits observed. Marketable fruit refers to saleable fruits, while Damaged/Injured is not, due to the lack of aesthetic qualifications. The pests causing fruit damage determined the Mite, Fruit Fly, and Hemiptera categories. And the Splotchy category could signify possible virus symptoms, by expressing splotchy patches on the fruit.

Hathor and Rona were the two varieties that produced the highest marketable yield throughout both trials (Figure 1). These two varieties, along with the remaining smaller tomato varieties 72618, Sarina, and 75125, generally had higher yields than the bigger tomato varieties: Katya, Shanty, Matty, 72103, V3051, 72061, 74956, Indigo Rose, Inbar, and Kewalo. In the Waialua trial Katya, Shanty, and Matty were the highest yielding bigger tomato varieties. Unfortunately the Kahuku trial was infected with late blight in the middle of the cropping season, and even though plants were treated, it caused a decline in tomato production for these varieties. Big tomato varieties 72103 and V3051 were globe and roma types that generally had the same marketable yield in both trials, despite late blight infection. Even though variety V3051 showed late blight resistance, it did have the highest unmarketable yield due to other factors in both trials (Figure 2 & 3). Kewalo, which was susceptible to TYLCV only, was the lowest yielding tomato variety in both trials. The susceptible control Indigo Rose generally had a lower yield than the other tomato varieties.

For the smaller tomato varieties such as Hathor, Rona, 72618, 75125, and Sarina, the marketable yield was generally greater than the unmarketable yield for both Waialua and Kahuku trials (Figure 2 and 3, respectively). For the bigger tomato varieties the opposite trend was observed; the unmarketable yield was generally greater than the marketable yield (Figure 2 and 3). The categories Mite, Fruit Fly, and Hemiptera (Figure 4 and 5), were the most important unmarketable categories. A regular commercial treatment for the damaging pests can potentially reduce the unmarketable yield in these categories.

• Figure 1
• Table1
• Figure 5
• Figure 2
• Figure 3
• Figure 4

Impacts and Contributions/Outcomes

An extension article entitled “Field screening of tomato varieties resistant to Tomato Spotted Wilt Virus and Tomato Yellow Leaf Curl Virus in Hawaii” was produced and it is part of the December 2014 CTAHR Sustainable Agriculture and Organic Program H?nai?Ai Newsletter (to be realeased in website: http://www.ctahr.hawaii.edu/sustainag/news/index.html, in January 2015).

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