Author
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Gulya Jr, Thomas |
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Submitted to: Proceedings Sunflower Research Workshop
Publication Type: Proceedings Publication Acceptance Date: 2/1/2001 Publication Date: N/A Citation: N/A Interpretive Summary: Field evaluations of three promising fungicides (azoxystrobin, zoximide, fenamidone) were made at 26 locations (in five U.S. states and in Canada, Hungary and Argentina) to assess control of sunflower downy mildew (Plasmopara halstedii). Twenty treatments were tested, including different rates and combinations of fungicides, plus comparisons with the four currently registered fungicides of Allegiance, Apron-XL, Maxim and Captan. Downy mildew developed at only two of 24 locations (Wahpeton and Minot, ND). The lack of rainfall immediately after planting is suspected to be the major cause for lack of mildew infection in the remaining locations. None of the fungicide treatments gave 100% control, nor did they perform as well as greenhouse trials would have predicted. Fenamidone at 200 g ai/100 kg (=3.2 oz ai/cwt) was the most effective treatment with 8% infection averaged over two locations, compared to 62% infection on the untreated control and 60% infection on Apron-XL treated seed. The combinat ion of azoxystrobin at 1/2 oz ai and zoximide at 2 oz ai/cwt had 21% infection, averaged over the two locations, compared to 1% in greenhouse trials. Future field evaluations of fungicide efficacy will utilize drip irrigation to insure waterlogged soil conducive for mildew infection, and supplementary inoculum applied through the irrigation hose. Modifications of greenhouse fungicide tests, detailed in the paper, should allow more accurate prediction of field performance of fungicides. Technical Abstract: Field evaluations of three promising fungicides (azoxystrobin, zoximide, fenamidone) were made at 26 locations (in five U.S. states and in Canada, Hungary and Argentina) to assess control of sunflower downy mildew (Plasmopara halstedii). Twenty treatments were tested, including different rates and combinations of fungicides, plus comparisons with the four currently registered fungicides of Allegiance, Apron-XL, Maxim and Captan. Downy mildew developed at only two of 24 locations (Wahpeton and Minot, ND). The lack of rainfall immediately after planting is suspected to be the major cause for lack of mildew infection in the remaining locations. None of the fungicide treatments gave 100% control, nor did they perform as well as greenhouse trials would have predicted. Fenamidone at 200 g ai/100 kg (=3.2 oz ai/cwt) was the most effective treatment with 8% infection averaged over two locations, compared to 62% infection on the untreated control and 60% infection on Apron-XL treated seed. The combinat ion of azoxystrobin at 1/2 oz ai and zoximide at 2 oz ai/cwt had 21% infection, averaged over the two locations, compared to 1% in greenhouse trials. Future field evaluations of fungicide efficacy will utilize drip irrigation to insure waterlogged soil conducive for mildew infection, and supplementary inoculum applied through the irrigation hose. Modifications of greenhouse fungicide tests, detailed in the paper, should allow more accurate prediction of field performance of fungicides. |
