WHITE SPOT: A NEW EMERG­ING DIS­EASE IN CORN

Agriculture - - Research -

A WHITE SPOT DIS­EASE, ear­lier de­scribed as Phaeosphaeria Leaf Spot was first ob­served in Brazil in 1982. Later on, the dis­ease was re­ported in South and Cen­tral Amer­ica, South Africa, and Asia. Early stage of in­fec­tion is char­ac­ter­ized by the pres­ence of small, pale green spots on the leaf sur­face (Fig­ure 1). Ad­vanced symp­tom of the dis­ease in­cludes bleached le­sions caus­ing blight of the whole leaf (Fig­ure 2). Sim­i­lar type of dis­ease was first ob­served in Bukid­non in 2014 after a week of con­tin­u­ous light rain and foggy weather con­di­tion. Since then, se­vere in­fec­tion is com­monly ob­served in corn fields with mid-el­e­va­tions (350-955 masl) through­out the grow­ing sea­son. Aside from field corn, the dis­ease also af­fects sweet and waxy corn.

Sev­eral pathogens have been re­ported as causal agents of the white spot dis­ease, which in­clude Pan­toea ana­natis; Phaeosphaeria may­dis (anamorph: Phoma may­dis); Scleroph­thora; and Phyl­losticta sp., Phoma sorghina, Sporormiella sp. dis­ease com­plex. The use of re­sis­tant va­ri­eties if avail­able, ap­pli­ca­tion of fungi­cides such as man­cozeb (e.g. Dithane) or pyr­a­clostrobin (e.g. Cabrio) and re­moval of in­fected crop residues after each crop­ping sea­son are among the prac­ti­cal means of white spot dis­ease man­age­ment.

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