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Poster Presentations


Poster Presentations


In vitro and greenhouse trials of the fungicides chlorothalonil and tebuconazole

Presenter: J. Marois

All authors and affiliations: B. Leite, J. MAROIS, and D. Wright. NFREC, IFAS, University of Florida, Quincy, FL 32351

Phakopsora pachyrhizi urediniospores were exposed to dilutions of fungicide formulations: chlorothalonil, tech. and Echo®, and tebuconazole, tech. and 3.6 F. Germ tube inhibition and the effect on appressoria formation were evaluated. Echo® and chlorothalonil tech. were clearly the most active fungicides. Echo® reduced germ tube formation in all dilutions tested. Chlorothalonil tech. was not as effective at the dilutions of 10(^–3) and 10(^–4). Tebuconazole tech. and 3.6 F were marginal to poor in the germ tube inhibition test and fair for appressoria inhibition. Under greenhouse conditions, soybean plants were sprayed with the same formulations. Plants were treated 3 days prior to inoculation with P. pachyrhizi. Urediniospores were applied over the leaves (3 ml of a 40,000 urediniospores/ml suspension), followed by a period of 18 h in a humidity chamber. Evaluation was performed 30 and 60 days after inoculation. Chlorothalonil tech. did not affect the rust. Tebuconazole (tech. and 3.6 F) apparently protected plants but resulted in reduced plant growth. Echo® was considered the best fungicide formulation. Secondary influence on the plants metabolism would never have been detected without the greenhouse trial. Tebuconazole influence on plant growth requires further investigation. It is possible that these effects are only effective during early stages of plant development. Tebuconazole is known to have plant growth regulatory activities on flax (Linum usitatissimum).

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