Viruela de la Alfalfa (Pseudopeziza medicaginis)

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Condición fitosanitaria: Presente

Grupo de cultivos: Forrajeras

Especie hospedante: Alfalfa (Medicago sativa)

Etiología: Hongo. Necrotrófico

Agente causal:  Pseudopeziza medicaginis  (Lib.) Sacc.

Taxonomía: Fungi > Dikarya > Ascomycota > Pezizomycotina > Leotiomycetes > Helotiales > Dermateaceae > Pseudopeziza

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Antecedentes

La viruela de la Alfalfa es la más frecuente de las enfermedades aéreas en la alfalfa. Ataca principalmente a plantas jóvenes y hojas inferiores. Las manchas son redondas, pardas, del mismo tamaño pero salpicando desigualmente las hojas. Suele presentarse en rodales aparentemente cloróticos. Los daños pueden ser importantes en alfalfares jóvenes que aún no tienen suficientes reservas.

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Sintomatología

Se observan manchas pequeñas pardo oscuro, de hasta 2-3 mm de diámetro, con bordes aserrados. En el centro de la mancha se forma un pequeño disco ó elevación hacia la cara superior del folíolo, que corresponde a la fructificación sexual del hongo (apotecio sésil). Las hojas severamente afectadas amarillean y caen. Durante períodos de tiempo húmedo, la defoliación puede ser severa y todas las hojas, excepto las más jóvenes, se desprenden de los tallos.

Los apotecios de Pseudopeziza medicaginis miden 200-320 µm de diámetro, en un principio subepidérmicos y luego erumpentes. Ascas en empalizada junto con parafisos, contienen ocho ascosporas aseptadas, hialinas y ovoides que
miden 8,7-9,5 µm de diámetro.

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Manejo Integrado de la enfermedad

Siembra de variedades de alfalfa tolerantes

Aplicación de fungicidas foliares

Adelantar el corte, segar muy bajo y retirar el forraje con la menor pérdida posible de hojas, ya que podrían reinfectar el suelo.

 

Videos

Scouting for Common Alfalfa Diseases in New York State

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Bibliografía

Alfalfa Common Leaf spot. UC Pest Management Guidelines

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