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United States Department of Agriculture

Agricultural Research Service

Research Project: Cool Season Grain Legume Genetic Enhancement and Pathology

Location: Grain Legume Genetics Physiology Research

Title: Pythium Root Rot (and Feeder Root Necrosis)

Author
item Chen, Weidong

Submitted to: Compendium of Corn Disease
Publication Type: Book / Chapter
Publication Acceptance Date: May 9, 2012
Publication Date: N/A

Interpretive Summary: Pythium species cause seed rot, damping-off, seedling blight and root rot of corn. Among these Pythium diseases, root rot presents the least conspicuous aboveground symptoms. Broadly defined, root rot also includes feeder root necrosis. Pythium root rot is considered an important cause of low corn yields in poorly drained soils and in soils with conservation tillage. At least 16 species of Pythium are known to cause root rot of corn. They generally overwinter in soil as oospores. Oospores germinate producing mycelium or sporangia which may then produce zoospores. Mycelium, sporangia and/or zoospores can infect corn roots causing root rot. Management of the disease include improving soil drainage, planting corn in soils with temperature >9 C and the use of fungicides in seed treatments.

Technical Abstract: Pythium species cause a number of diseases on corn. Among the Pythium diseases, root rot presents the least conspicuous aboveground symptoms. Broadly defined, root rot also includes feeder root necrosis. At least 16 species of Pythium are known to cause root rot of corn. These include P. acanthicum, P. ad¬haerens, P. angustatum, P. aphanidermatum, P. arrhenomanes, P. graminicola, P. helicoides, P. irregulare, P. paroecandrum, P. pulchrum, P. rostratum, P. sylvaticum, P. splendens, P. tardicrescens, P. ultimum, and P. vexans. They generally overwinter in soil as oospores that germinate producing mycelium and sporangia. The sporangia may then produce zoospores. Mycelium, sporangia and/or zoospores all can infect corn roots causing root rot. Management of the disease include improving soil drainage, avoiding planting corn in soils, and the use of fungicides in seed treatments. However, Pythium spp. and isolates of a given species vary in their sensitivity to different fungicides. Appropriate rotation or combinations of fungicides with different modes of action should be practiced to improve control efficacy and prevent development of fungicide resistance in Pythium spp. No resistance is known in corn hybrids and rotation has not been effective in managing Pythium root rot of corn.

Last Modified: 8/22/2014
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