Journal of General Plant Pathology

, Volume 84, Issue 4, pp 284–295 | Cite as

Direct antifungal activity of tiadinil, a systemic acquired resistance inducer, and thymol formulations on Stagonosporopsis citrulli and control of watermelon gummy stem blight

  • Yonas Kefialew
  • Sanju Kunwar
  • Dawit Abate
  • Amare Ayalew
  • James Colee
  • Laura Ritchie
  • Stephen M. Olson
  • Mathews L. Paret
Disease Control


This study evaluated the direct antifungal activity of tiadinil [N-(3-chloro-4-methylphenyl)-4-methyl-1,2,3-thiadiazole-5-carboxamide], a systemic acquired resistance (SAR) inducer and two formulations of thymol (thymol I and thymol II) against Stagonosporopsis citrulli, the causal agent of gummy stem blight (GSB) disease of watermelon. Tiadinil, thymol I and thymol II completely inhibited the mycelial growth of S. citrulli in vitro at ≥ 100 ppm. Conidial germination and germ tube elongation were completely inhibited by tiadinil at ≥ 2000 ppm and by thymol-based formulations at ≥ 100 ppm. A single foliar application of tiadinil at ≥ 10 ppm or a single application of thymol I and II at ≥ 1 ppm, 48 h before or after pathogen inoculation, significantly reduced disease severity of watermelon seedlings inoculated with 105/ml conidial suspension of S. citrulli, compared to respective nontreated controls. Plants treated with foliar application of tiadinil at ≥ 1000 ppm before pathogen inoculation had significantly lower disease severity than plants that received an equivalent drench application. The efficacy of foliar application of tiadinil was affected by concentration and frequency of application. The study suggests direct antifungal activity of tiadinil, indicating a new mode of action of tiadinil against GSB disease of watermelon. The study also demonstrated direct antifungal action of thymol, a formulated active compound of essential oils, against S. citrulli and GSB disease of watermelon.


Stagonosporopsis citrulli Fungicide resistance 1,2,3-Thiadiazole Novel antifungal compounds SAR with direct antifungal activity 



The authors would like to acknowledge the National Watermelon Association Grant 0010592 for funding and Addis Ababa University and the Ministry of Agriculture, Government of Ethiopia for financial support of YK as a graduate student who completed the work at the University of Florida, North Florida Research and Education Center (NFREC), Quincy, FL. The authors acknowledge Hank Dankers, Binoy Babu, Sheeja George and Jim Marois for their valuable support and guidance in the project and Dr. Botond Balogh, Nichino America, Inc. and Marcel Barbier, AgriMor Int’l Co. for their support in this research.


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Copyright information

© The Phytopathological Society of Japan and Springer Japan KK, part of Springer Nature 2018

Authors and Affiliations

  • Yonas Kefialew
    • 1
    • 2
  • Sanju Kunwar
    • 2
  • Dawit Abate
    • 3
  • Amare Ayalew
    • 4
  • James Colee
    • 5
  • Laura Ritchie
    • 2
  • Stephen M. Olson
    • 2
  • Mathews L. Paret
    • 2
  1. 1.Ethiopian Institute of Agricultural ResearchGambella Agricultural Research InstituteGambellaEthiopia
  2. 2.North Florida Research and Education Center, Institute of Food and Agricultural SciencesUniversity of FloridaQuincyUSA
  3. 3.Department of Microbial, Cellular and Molecular BiologyAddis Ababa UniversityAddis AbabaEthiopia
  4. 4.School of Plant SciencesHaramaya UniversityDire DawaEthiopia
  5. 5.Department of StatisticsUniversity of FloridaGainesvilleUSA

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