Foliar blight on Kalmia caused by Phytophthora syringae.
Photo by N. Grunwald.
Foliar leaf spots, shoot blight, and stem cankers.
|Foliar leaf spot on Rhododendron.
Photo by R. Linderman.
- Ash (Fraxinus)
- Crabapple (Malus)
- Flowering pear (Pyrus)
- Mountain laurel (Kalmia)
- Lilac (Syringae)
- Rhododendron (Rhododendron)
This disease is found wherever bare-root trees are grown, although development is favored by cool and misty conditions, such as foggy areas along waterways. Rhododendrons grown in containers and fields are also susceptible.
|Stem canker on crabapple
following winter infection with
Photo by R. Regan.
Rain splash from infested standing water spreads the pathogen. Plant tissue wounded by harvest or pruning is at increased risk of disease.
This pathogen survives as spores in soil and in fallen leaves; spores become active during prolonged periods of standing water.