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Disease Control and Pest Management

The Systemic Antifungal Activity of Ridomil against Phytophthora infestans on Tomato Plants. Y. Cohen, Associate professor, Department of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel; M. Reuveni(2), and H. Eyal(3). (2)(3)Ph.D. candidate, and technician, respectively, Department of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel. Phytopathology 69:645-649. Accepted for publication 8 January 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-645.

Ridomil® (dl-methyl N-[2,6-dimethylphenyl]-N-[2-methoxyacetyl] alaninate), a new systemic fungicide effective against plant pathogenic species of the Peronosporales, effectively controlled Phytophthora infestans on tomato plants. A single soil drench containing 0.25 mg a.i. applied to a 7-leaf plant in a 1 L pot was sufficient to protect plants against blight. Protection of potted plants treated by soil drench was observed within 1 hr from time of fungicide application at 25 C. The fungicide was slightly toxic to sporangia and zoospores in vitro. Penetration and initial establishment of P. infestans in leaves and fruits was not inhibited by the fungicide. Instead, minute, restricted, sterile lesions were produced, even if the compound was applied 2–3 days after inoculation. To achieve the most efficient control of blight, plants must be treated with the fungicide either before, or within the first 2 days after, inoculation.