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Pruning a rhododendron!

Why is my rhododendron wilting?

There are a few different causes of wilt on a rhododendron. The most common, of course, is drought. Here are a few others to watch for:

Botrytis Blight is caused by a fungus that overwinters in dead and decaying plant material. It begins sporulating when humidity levels get high and is spread through moving water.

Symptoms:

  • Spotted or discolored flowers
  • Bud rot
  • Discolored leaved and shoots will wilt, decay, and drop
  • Gray to brown spore masses on leaves

Control:

  • Remove and dispose of dead and decaying organic debris around plants
  • Prune and dispose of infected issues, making sure to disinfect pruners between cuts
  • Avoid overhead watering
  • Thin canopy of plant to increase air circulation

Whitefly infestation can go unnoticed until there are large colonies. The pupa and the adults will cause damage to the plants. They also favor wet, humid conditions for reproduction.

Symptoms:

  • Leaves curl, yellow and wilt
  • Honeydew turning to sooty mold on lower leaves
  • Flat, oval, transparent insects on undersides of leaves

Control:

  • Spray undersides of leaves with insecticidal soap if beneficial insects are present
  • Use indicated insecticide as directed

Phytopthora Root Rot is the most common fungus in rhododendrons because of the growing conditions needed for healthy plant growth. It is a parasitic fungus that attacks water conducting tissues, spreading through wet soils.

Symptoms:

  • Brittle brown to reddish brown leaves
  • Yellowing at shoot tips
  • Rolling or wilting leaves
  • Slowed growth and limb dieback

Control:

  • Low pH (4.5) will suppress spore release
  • Remove infected plant tissues, disinfecting between cuts
  • Improve drainage in root area by adding peat or perlite
  • Beneficial mycorrhizae applications to soil will help strengthen roots and prevent infection
  • Use approved fungicide applications, soil first, then plant.

Do not over-fertilize! Nitrogen pushes growth that will be tender and easily colonized by fungus. Treat problems first, fertilize when plants have recovered.

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