Spruce trees showing signs of decay may be suffering from needle cast disease, which has been spreading at a faster rate in recent years due to cold and wet weather in springs. Needle cast disease is caused by two different types of fungi: Rhizosphaera kalkhoffii or Stigmina lautii. These fungi affect the needles of spruce trees, most commonly on Blue Spruce and White Spruce, but all spruce trees are susceptible to needle cast disease.
Signs of needle cast disease
- Needles turn brown to purplish-brown
- Small black spots can be seen with 10x hand lens on the stomata of needles
- Discoloration begins near lower end of tree on interior older needles
- Moves outward on the branches to newer needles and up the tree
- Needles and branches affected eventually die
Needle cast can eventually kill the tree. It usually takes three to five years.
The following treatment options are available for needle cast disease:
- Fungicide sprays can be used
- Timing is crucial
- Only preventative
- Will not get rid of fungus just prevents the spread
- Recurring annual treatments
- Two to three treatments a year in the spring
- Raking and removal of old needles and branches on ground
- Removal of affected branches
- Increase airflow
- Increase space between multiple trees
- Prune branches near the base of the tree
- Remove affected trees to help prevent spread
- If needle loss is significant enough to have lost screening capabilities or desired aesthetic, removal is better option
- Spruce trees do not regenerate well and will struggle to ever replace the needles that were lost
Contact an ISA Certified Arborist to evaluate your spruce trees if you have concerns about them. You may use treesaregood.org/findanarborist. If your arborist determines chemical application is the best treatment, verify that they are licensed by the Ohio Department of Agriculture to perform this treatment.
If you have questions or would like more information, you may contact the City of Dublin Forestry Division by calling 614.410.4701 or online here- https://dublinohiousa.gov/contact-us/contact-forestry/.