Downy mildew of poppy

Peronospora arborescens

Symptoms occur as angular, chlorotic to necrotic spots on the upper leaf surface, distorted growth and eventually a purplish, downy growth on undersides. Monitor greenhouses regularly for symptoms of Downy Mildew. Control depends on fungicide applications, the use of resistant cultivars, and cultural practices. Minimize periods of leaf wetness by reducing density of the plant canopy and avoiding overhead irrigation. High humidity, prolonged leaf wetness, and cool weather favor the development of Downy Mildew diseases. Heat and vent greenhouses in evening and early morning, especially when warm days are followed by cool nights, to reduce relative humidity. Once infection is established, sporangiophores emerge from the stomata on leaf undersides and sporangia are easily spread by splashing water,wind, or handling.

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