Powdery mildew on roses

Powdery mildew is one of the most prevalent and common diseases of roses caused by the fungus sphaerotheca pannosa var.rosae, This results in the production of white powdery fungal growth over the surface area of leaves and stems and at times the flower heads. Severe infected leaves turn yellow or brown and become wrinkled, eventually dying. The disease can also disfigure flowers and new rose buds.

Powdery mildew is favored by warm dry days followed by cool humid nights. If left unchecked, the microscopic spores spread quickly to the other unaffected plants.

Weather conditions
Powdery mildew is prevalent during dry summers at a temperature between 16- 27C which make conditions favorable for development and spread of the spores.

Characteristics of affected plants

  • The affected leaves may appear discolored, curled or distorted.
  • The white powdery fungal growth can be sighted on stems, flower stalks, leaves, sepals and petals in severe cases.
  • The affected plant experiences decreased plant growth and vigor due to reduced photosynthetic efficiency.
  • In severe cases the leaves fall off.

Natural control

  • Roses should be well spaced while planting to allow easy transpiration.
  • The greenhouses should be well ventilated for circulation of air.
  • Watering should be done properly to avoid water logging and soils aerated during the cold season.
  • Plant disease resistant varieties.

Chemical control
This is the most effective way to prevent and eradicate the spores. Spot checks are done for early detection and to ensure timely control measures are taken.

Trustmate Xtreme 300 EC 0.4ml/L, Sacrifido 125 EC 1ml/L, Milestone 250 SC 0.75ml/L, Sparrow 500EC 0.75 ml/L, Monument 400 EC 2.5ml/L, Longstar 40 EC 0.2ml/L, Bradley 500 SC 0.5ml/L, Absolute 375SC 0.5ml/L, Discovery 400SC 0.5ml/L, Sahara 0.2ml/L, Souvenir 80WDG 2.5g/L, Jupiter 125 EC 0.75ml/L, Domain 25 EW 0.75ml/L, Cantona 230 EC 1ml/L.

Tank mix all products with Integra/ Agrigold 0.2ml/L for better coverage.

Source: Greenlife

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