Spring is coming fast and people are starting to spend more time out in their yards and gardens. One of the most notable species to look at right now is evergreens, as most other plants are dormant. Every year I get calls from clients saying that their blue spruce trees that were planted 20 years ago are starting to look thin and ragged, and losing needles from the bottom up. Most of the time, this is a fungal disease called Rhizophaera Needle Cast. 

Once spruce trees reach 15-20 years old, they become very vulnerable to a disease called Rhizosphaera Needle Cast. Colorado Blue Spruce are the most vulnerable to this fungal disease. This disease is very prevalent in the area due to the very humid Wisconsin environment. Fungal spores grow at the highest rate during warm and wet weather.

Spruce trees are ideally planted on sites with acidic, moist, well drained soils and full sun. This mimics their natural environment and reduces stress levels. Trees planted on poor sites are more likely to be infected with Rhizosphaera needle cast due to prolonged stressful conditions. Most Outagamie county soils have poor drainage, heavy clay base, and are alkaline, which aren’t ideal conditions for spruce species. This doesn’t mean that they can’t grow here, but they are more likely to become infected over time. Drought and other factors can also stress trees. 

Impacted trees will start losing needles from the bottom up, and the inside out. Needles may also take on a purplish coloring. Infected needles will also have rows of small, black spheres form along the length and are visible with a 10X hand lens. These black spheres are fruiting bodies (i.e., reproductive structures) of the fungus that causes the disease and are diagnostic.

These fungal spores are spread through splashing water, avoid overhead watering such as sprinklers. Trees can be protected from needle cast with properly timed fungicide applications. Affected trees can be treated with fungicides labeled for use on evergreens and containing copper or chlorothalonil. Treatments will not cure existing infections, but can prevent additional infections. Read and follow label directions. 

Other things that can be done to limit infection and prolong the life of the tree include:

The disease also affects other conifers including black, Engelmann, Serbian, Sitka, and White (Black Hills) spruce; Austrian, mugo and eastern white pine; Douglas-fir, balsam fir and western hemlock.

For more information, please visit: https://hort.extension.wisc.edu/articles/rhizosphaera-needle-cast/ 

Don’t Spring Into Garden Cleanup

As the temperatures begin to rise, it is easy to find yourself wandering around the yard looking for something to do, but hold off on cleaning out perennial beds. The garden is a hot spot of insect activity in early spring!

Wait to clean up the garden until temperatures are consistently over 50 degrees at night. This allows time for overwintering insects (in twigs, leaf debris, and underground) to emerge and take up their role in the ecosystem.

Something eating your plant? Need help identifying a tree? Interested in the best way to care for your lawn? Submit your questions online!

920-832-4764
Kaitlin.Bricco@wisc.edu

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