New data shows need for an integrated approach to bacterial spot management in Ontario tomato production

Cheryl Trueman, College Professor, Ridgetown Campus, University of Guelph

Producers of transplants for field production of fresh market and processing tomatoes typically use regular applications of copper hydroxide (Kocide 2000 or Coppercide WP) to manage bacterial diseases during greenhouse production. The efficacy of this standard practice and other potential new management tools for bacterial spot (Xanthomonas gardneri) were recently evaluated at Ridgetown Campus, University of Guelph.

What we did:

  • Each plot consisted of tomato seedlings (cultivar TSH32) growing in one half of a 200-cell tray (approximately 100 plants). Plots were separated by barriers 40 cm in height to prevent interference from neighbouring trays (Figure 1).
  • Product application descriptions are summarized in Table 1. Products tested included:
    • Kocide 2000 (copper hydroxide 53.8%)
    • KleenGrow (didecyl dimethyl ammonium chloride 7.5%)
    • Actigard (acibenzolar-S-methyl 50%)
    • Actinovate (Streptomyces lydicus strain WYEC 108 1 x 107 cfu/g)
    • AEF 1301 (unknown)
    • Cyclone (lactic acid 10.73 g/L, citric acid 21.37 g/L; present as fermentation products of Lactobacillus casei strain LPT-111)
    • Zerotol (hydrogen peroxide 27%).
  • Trays were inoculated by replacing one healthy seedling at the center of each tray with one seedling inoculated with a copper-sensitive strain of Xanthomonas gardneri and showing symptoms of bacterial spot.
  • The area of the tray with bacterial spot symptoms was monitored over time.

Figure 1. Experimental plot showing location of inoculation with symptomatic seedling, spread of bacterial spot symptoms from inoculation point, and barriers used to separate plots.
Figure 1. Experimental plot showing location of inoculation with symptomatic seedling, spread of bacterial spot symptoms from inoculation point, and barriers used to separate plots.

 

Table 1. List of products tested and application timings.
Table 1. List of products tested and application timings.

What we found:

  • Foliar applications of Kocide 2000, with or without the Actigard seed treatment, had a smaller area of bacterial spot symptoms than the inoculated control 26 days after inoculation in 2014. However, 10 to 30% of the tray area still had disease symptoms in these treatments.
  • None of the treatments reduced the area with bacterial spot symptoms compared to the inoculated control in 2015.
  • Foliar applications of KleenGrow, Actinovate, AEF1301, Cyclone, and Zerotol, and seed treatment with Actigard (without Kocide 2000) did not effectively reduce disease spread.

Conclusions: Kocide 2000 reduced the spread of disease spread in one of two years, but the level of disease in the treated trays was still at a level of economic concern. Therefore, it is important to include other methods for bacterial spot management during tomato transplant production such as good pre-season and in-season sanitation practices, use of clean seed, and practices that limit periods of leaf wetness.

Figure 2. Area of transplant tray with bacterial spot symptoms 26 days after inoculation with one symptomatic tomato seedling, 2014. Columns with the same letter are not significantly different from each other (P ≤ 0.05), Tukey’s HSD.
Figure 2. Area of transplant tray with bacterial spot symptoms 26 days after inoculation with one symptomatic tomato seedling, 2014. Columns with the same letter are not significantly different from each other (P ≤ 0.05), Tukey’s HSD.

 

Figure 3. Area of transplant tray with bacterial spot symptoms 26 days after inoculation with one symptomatic tomato seedling, 2015. Columns with the same letter are not significantly different from each other (P ≤ 0.05), Tukey’s HSD.
Figure 3. Area of transplant tray with bacterial spot symptoms 26 days after inoculation with one symptomatic tomato seedling, 2015. Columns with the same letter are not significantly different from each other (P ≤ 0.05), Tukey’s HSD.

For more information or to request a full copy of the research report please contact Cheryl Trueman (ctrueman@uoguelph.ca).

Acknowledgements: The Ontario Farm Innovation Program is funded through Growing Forward 2 (GF2), a federal provincial-territorial initiative. The Agricultural Adaptation Council assists in the delivery of GF2 in Ontario. Portions of this work were also sponsored by the Fresh Vegetable Growers of Ontario and the Ontario Tomato Research Institute.

Acknowledgements

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