Causal Agent: 

Fungus (Podosphaera xanthii holomorph Oidium)

Characteristic Symptoms:

Whitish, powdery fungal growth develops on both leaf surfaces and on petioles, and stems.

Infected leaves usually wither and die causing premature senescence of melon plants.
Conditions for Disease Development
Disease emergence is favored by dry weather and high relative humidity.
Favorable conditions include dense plant growth and low light intensity.

The primary source of inoculum is the airborne conidia which are dispersed over long distances.

Management and Control:
Use of resistant varieties, if available.
Maintain good field sanitation (e.g. remove & burn plants/plant parts as soon as symptoms are observed).
Follow proper plant spacing.
Avoid too much application of nitrogenous fertilizer.
Apply fungicides such as  thiophanate methyl (e.g. Tango®, Topsin®), azoxystrobin (Amistar®, MiradorⓇ, RobatoⓇ), difenoconazole (e.g. ScoreⓇ, MontanaⓇ, PursueⓇ, BashⓇ), tebuconazole (e.g. Folicur®) or  sulfur-based fungicide  (e.g. Kumulus®), or thiophanate-methyl (e.g. Tango, Topsin®), cartap hydrochloride (e.g.  PadanⓇ, Barena 50 SP, Gemtrak®), acetamiprid (e.g. MospilanⓇ), acephate (e.g. AcetamⓇ, CompeteⓇ), chlorphenapyr (e.g. Kotetsu) or penthoate (e.g. PennantⓇ, VidexⓇ).


Compendium of Cucurbit Diseases (2010) by The American Phytopathological Society

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