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Suppression of Sclerotinia Stem Rot of Soybean by Lactofen Herbicide Treatment

July 1999 , Volume 89 , Number  7
Pages  598 - 602

E. K. Dann , B. W. Diers , and R. Hammerschmidt

First and third authors: Department of Botany and Plant Pathology; second author: Department of Crop and Soil Sciences, Michigan State University, East Lansing 48824

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Accepted for publication 20 April 1999.

Severity of Sclerotinia stem rot of soybean after treatment with lactofen (Cobra) and other herbicides was assessed in field experiments conducted in Michigan from 1995 to 1997. At sites where disease pressure was high, disease severity was reduced 40 to 60% compared with controls when lactofen was applied at the V3 (1995 and 1996) or R1 (1997) growth stages. Corresponding seed yields were unchanged or up to 20% greater when lactofen was applied at the R1 stage in 1997. Disease severity was not reduced by lactofen treatments in years and at sites where disease pressure was low to medium, and corresponding yields often were reduced by ≈10%. High levels of glyceollin accumulated in lactofen-injured leaves collected from field plots in 1996 and 1997. High glyceollin content in lactofen-treated leaves was associated with significant reductions in lesion size when leaves were challenge-inoculated with Sclerotinia sclerotiorum.

Additional keywords: diphenyl ether, protoporphyrinogen IX oxidase, Protox, white mold.

© 1999 The American Phytopathological Society