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Evaluation of Control Efficacy of Phosphorous Acid Against Sweet Potato Foot Rot
Effect of neutralized phosphorous acid solution (NPA) with different concentrations on the mycelial growth of <i>Phomopsis destruens</i> on potato dextrose agar (PDA) medium at 20℃ for 20 d. (A) control, (B) 2.00 g L<sup>-1</sup>, (C) 1.00 g L<sup>-1</sup>, (D) 0.50 g L<sup>-1</sup>, and (E) 0.33 g L<sup>-1</sup>.
Effect of neutralized phosphorous acid solution (NPA) with different concentrations on the mycelial growth of Phomopsis destruens on potato dextrose agar (PDA) medium at 20℃ for 20 d. (A) control, (B) 2.00 g L-1, (C) 1.00 g L-1, (D) 0.50 g L-1, and (E) 0.33 g L-1.

Author:Yu-Ping Liang, Ching-Yi Lin, Chao-Jung Wu, and Hui-Fang Ni*

Abstract:

    Sweet potato foot rot caused by Phomopsis destruens is a serious disease of sweet potato recently in Taiwan. Currently, preventing this disease in the fields relies on these methods, including planting healthy seedlings combined with flooding before planting, applying chemical fungicides and other control techniques. In order to provide an environmentally friendly method of disease control for organic or eco-friendly farming system, this study evaluated the control efficacy of neutralized phosphorous acid solution (NPA) against P. destruens through in vitro and greenhouse trails. In vitro studies showed that mycelial growth and spore germination of P. destruens were significantly inhibited by 0.33–2.00 g L-1 NPA, and the inhibition of mycelial growth and spore germination were the highest (85.1% and 98.9%, respectively) while it was applied with 2.00 g L-1 NPA. In greenhouse trials, NPA was applied with different concentrations, application dosages, timings and times to pathogen-inoculated variety ‘TN-71’ seedlings to evaluate its control efficacy. The results showed that NPA could control the disease only in higher concentration (2.00 g L-1 and 1.00 g L-1), and the application dosage should be over 60 mL. The application timing of NPA was the best at 1 wk after inoculation, while applying NPA at 2 or 3 wk after inoculation showed lower control efficacy. For application times, applying 1, 2 or 3 times all showed significant control efficacy. This study showed that NPA might have direct inhibition effect on P. destruens, and its control efficacy against sweet potato foot rot disease was confirmed through greenhouse trials. In conclusion, this study proved that NPA could be applied as a low-toxic protectant for non-pesticide or organic farming systems to control sweet potato root rot in the field.

Key words:Sweet potato (Ipomoea batatas), Foot rot disease, Phomopsis destruens, Phosphorous acid

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Journal of
Taiwan Agricultural Research
Vol. 73, No.1 (2024) ISSN: 2790-086X Vol. 73, No.1 (2024)
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