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Ministry of Agriculture, Food and Rural Affairs

Powdery Mildew

Powdery mildew Powdery mildew (underside of leaf) Powdery mildew - advanced (underside of leaf)
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Beginner

Scientific Name
Leveillula taurica

Identification

  • A brownish powdery growth is produced on the underside of the leaves
  • The upper leaf surface may develop yellow patches
  • In severe cases, the leaf turns completely yellow and drops off
  • Symptoms appear on older leaves first

Often Confused With
N/A

Period of Activity
Powdery mildew of peppers can develop over a wide range of temperatures in low or high humidity conditions.  It can develop as early as late June.

Scouting Notes
It takes close examination to detect early signs of this disease in peppers.  In the early stages, no sign of the disease is present on the upper leaf surfaces.

Thresholds
None established.

Advanced

Scientific Name
Leveillula taurica

Identification
The organism that causes pepper powdery mildew grows within the leaf and produces spores on the underside of leaves.  Although powdery mildew typically appears as a white powdery growth on most plants, it may actually appear brown on pepper leaves.  The upper leaf surface may develop yellow spots, eventually turning completely yellow and dropping off in severe cases.  Symptoms appear on older leaves first.

Often Confused With
N/A

Biology
The pathogen that causes powdery mildew in peppers has a wide host range which includes tomato, however it has not been found to infect tomato in our growing region.  Powdery mildew found infecting tomato in the northeast U.S. and Ontario has been caused by a different organism.  Yet another organism causes powdery mildew of cucurbits.  The organisms infecting tomato and cucurbits can produce spores on both the upper and lower leaf surfaces.

Period of Activity
Powdery mildew of peppers can develop over a wide range of temperatures in low or high humidity conditions.  Due to its wide host range, it can be difficult to control with cultural practices.

Scouting Notes
It takes close examination to detect early signs of this disease in peppers.  In the early stages, no sign of the disease is present on the upper leaf surfaces.

Thresholds
None established.

Management Notes

  • Some varieties have resistance or tolerance to powdery mildew.
  • The fungicides that control other pepper fungal diseases are not effective on powdery mildew.  Powdery mildew specific fungicides must be used, and spray coverage of the underside of leaves and the lower canopy is important.
  • Due to its wide host range, powdery mildew can be difficult to control with cultural practices.