Cause Pseudomonas syringaepv. viburni, a bacterium that can be a
problem in cool, wet springs. Pseudomonas syringaepv.
Symptoms Spots are at
first water soaked, then turn brown and irregular in shape. Oregon observations
are that spots may be angular. Margins frequently develop a bacterial exudate.
Numerous spots during early shoot growth can deform leaves. Stem lesions are
elongate and generally not as obvious. Severe infections can result in a shoot
Remove and destroy infected leaves or plant debris.
Space plants for good air circulation.
Avoid high nitrogen fertility that promotes excessive growth.
Protect plants from extremes of weather early in the season.
Plastic shelters have been as good as or better than chemical methods against
the same disease on other crops.
Cultivars reportedly resistant include V. x burkwoodii`Mohawk`, V.
x carlcephalum`Cayuga`, V. lantana `Mohican`, and V. rhytidophyllum`Alleghany`.
Bacteria resistant to copper
products have been detected in many nurseries.
Copper-Count-N at 1 quart/100 gal water. Oregon only. 48-hr
CuPRO 2005 T/N/O at 0.75 to 3 lb/A (or 1 to 3 Tbsp/1000 sqft)
dormant or at 0.75 to 2 lb/A when new growth is present. 24-hr reentry.
Junction at 1.5 to 3.5 lb/A. 48-hr reentry.
Monterey Liqui-Cop at 3 Tbsp/gal water.