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United States Department of Agriculture

Agricultural Research Service

Title: A Survey for the Prevalence and Distribution of Cercospora Beticola Tolerant to Triphenyltin Hydroxide and Resistant to Thiophanate Methyl

Authors
item Smith, Garry
item Campbell, Larry
item Lamey, H - NORTH DAKOTA STATE UNIV.

Submitted to: Sugarbeet Research and Extension Reports
Publication Type: Proceedings
Publication Acceptance Date: November 1, 1996
Publication Date: N/A

Interpretive Summary: Triphenyltin fungicides (hydroxide, chloride, or acetate) have been very effective against Cercospora beticola L. For the control of leaf spot on sugarbeet. Triphenyltin hydroxide (TPTH) is superior to copper and carbamate fungicides in toxicity and persistence on leaves and has been used extensively in the Northern Plains of the United States, where Cercospora leaf spot is a problem. TPTH usage increased dramatically after the rapid development of strains that became resistant tot he benzimidazole class of fungicides in the early 1980s in Minnesota and North Dakota. TPTH now is the primary fungicide for control of Cercospora leaf spot on sugarbeets.

Technical Abstract: Triphenyltin fungicides (hydroxide, chloride, or acetate) have been very effective against Cercospora beticola L. For the control of leaf spot on sugarbeet. Triphenyltin hydroxide (TPTH) is superior to copper and carbamate fungicides in toxicity and persistence on leaves and has been used extensively in the Northern Plains of the United States, where Cercospora leaf spot is a problem. TPTH usage increased dramatically after the rapid development of strains that became resistant to the benzimidazole class of fungicides in the early 1980s in Minnesota and North Dakota. TPTH now is the primary fungicide for control of Cercospora leaf spot on sugarbeets. We began testing field isolates of C. Beticola in our laboratory in 1986 for tolerance to TPTH and obtained negative results until 1994. Tests of conidia from leaf spots suggested that the fungus had developed tolerance to the fungicide. In 1995 and again in 1996, extensive surveys were made in the Red River Valley and Southern Minnesota extending to the Canadian border. Leaf samples were collected from fields in seven factory districts. These samples were tested in the USDA-ARS laboratory in Fargo to determine the prevalence and distribution of strains of C. beticola exhibiting tolerance to TPTH as well as resistance to benzimidazole-type fungicides represented by thiophanate methyl (TM).

Last Modified: 9/22/2014
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