Blue Spruce with Needle Cast Disease
I have recently removed a 40-50 year old Blue Spruce that was rapidly losing its needles due to Needle Cast disease. I did try treatment but it didn't respond too well so I reluctantly had it removed. I would like to replace it with another Spruce, preferably a Blue. My questions are as follows...(1) How long should I wait before planting in the same location of the previous diseased tree? (2) Should I treat the soil before doing so? (3) If I should apply treatment, what should I use? (4) If you don't think a Blue is a good idea, then what Spruce would you recommend? (5)What size tree should I plant so the deer don't ravage it, as deer are a problem in my neighborhood?
Here are the answers to your questions:
1) You do not need to wait before planting in the same location. The needle cast pathogens are airborne, not in the soil.
2) There is no need to treat the soil.
3) If you decide to treat your new tree with a fungicide, you may need to treat as often as every 10 days (following your product label) depending on weather conditions. For most homeowners, this is neither practical nor desirable.
4) Blue spruces are not native nor adapted to our area and they do not like our region's hot and humid summers. They can look great for 10 years or so but they often decline over time. There are several alternatives to blue spruces listed at the bottom of this page on our website: https://extension.umd.edu/hgic/topics/cytospora-canker-spruce
Also, here is a related article written by our plant pathologist. https://marylandgrows.umd.edu/2018/01/08/whats-wrong-with-my-blue-spruce-tree/