Ramorum Shoot Dieback
Phytophthora ramorum
0 host plants
Last updated
This profile synthesizes data from multiple published sources. Expert field review is in progress.
Symptoms associated with Phytophthora ramorum infections include needle blight, a shoot blight resulting from needle infections, and stem lesions resulting from the growth of the pathogen from infected newly emerging needles/shoots into older wood. Symptoms are similar to Botrytis shoot blight on young seedlings.
Remove infected material promptly and improve air circulation. Avoid overhead irrigation that prolongs leaf wetness. For persistent problems, consult WSU Extension for current treatment recommendations.
Quick Reference
Management
Peak activity during cool, wet springs (March-May in the Puget Sound region) when daytime temps are 50-65°F and leaf wetness persists. Also active in fall (September-November) during wet weather. Dormant in hot, dry summers and below-freezing winters. P. ramorum requires moisture and 50-65°F for optimal infection. # Source: PNW Plant Disease Management Handbook
Cool (50-65°F), wet conditions; persistent leaf wetness from rain or overhead irrigation; higher humidity from dense plantings; susceptible host species including rhododendrons, Pieris, Viburnum, Camellia, Kalmia. # Source: PNW Plant Disease Management Handbook - Ramorum Leaf Blight and Shoot Dieback
Cultural Controls
- Avoid conditions that promote long moist foliage conditions such as overhead watering, evening watering, and planting too close to a fence.
- Give plant adequate spacing.
- Avoid overwatering plants by watering deeply but infrequently.
- During dry summer months, allow the soil to drain and dry out between waterings.
- Do not plant junipers in poorly draining soils.
- Improve drainage when possible.