|
|
Cytospora canker (fungus) |
Widespread and serious, especially on Colorado blue and Norway spruces. Needles on affected branches turn light gray or brown and die. Bluish-white resin encrusts bark of branches or main trunk. |
(See the PDC Fact Sheet "Twig Blights and Cankers".) Promptly cut out and destroy dying branches. Trim back to trunk or nearest healthy lateral branch. Do not prune in wet weather. Disinfect pruning tools between cuts. |
|
| Rhizosphaera needlecast (fungus) |
 |
Older needles turn purplish brown. Younger needles remain green. Usually affects 2-year-old needles, but other needles sometimes affected. Branches may die after three or four years of defoliation.
 |
Prune surrounding vegetation to increase air circulation. Spray with Bordeaux mixture or chlorothalonil when needles are 1/2 inch to 2 inches long. Repeat as label directs. (See resistant varieties). |
|
|
Spider mite feeding injury |
Foliage may appear off-gray-green. Severely affected branches may die. |
See MU publications G 7274 and G 7273 |
|
| University Outreach and Extension does not endorse commercial products. Follow the label on all pesticides. |
