White Pine - needles turning brown
Dear Expert, Our pines were always very healthy. For the past couple of months, the lower branches of one Eastern White Pine tree have started to turn brown. It looks like it is spreading to another tree. Looking closely, there are white spots on the needles. The affected branches are cracked open with black wounds, oozing sap. Could this be a fungus or a parasite? If yes, would it help to cut the affected branches off? Do you recommend any sprays for treatment? Thank you very much. Regards,
The pine tree in the left photo is declining and fading out. The tree most likely started to decline in the fall. Evergreens in general can stay green for a while before they decline. The tree may have declined due to several reasons such as poor drainage, girdling roots, drought, soil compaction, etc. The trees are also planted closely together and there is a lot of root competition for moisture and nutrients.
The last several years has been difficult for woody plants. We had abnormal rainfall in 2018 and the spring of 2019. Saturated soil reduces oxygen for the roots and the roots dieback. We also had a drought last season and this was the tipping point for many woody plants. Drought affects the root system as well.
The middle photo looks like a possible scale insect on the foliage. This is a secondary insect and not the cause for decline.
Right photo shows old damage to the trunk and branches. We cannot say from what but the tree needs to be removed. There is no control.
In general, bark beetles can attack stressed trees. Remove them from the property and keep the remaining trees as healthy as possible. Water the trees during dry periods and make sure the soil drains well. Mulch should be no thicker than several inches and away from the base of the trunk. Here is our publication on pine for more information https://extension.umd.edu/sites/extension.umd.edu/files/_images/programs/hgic/Publications/HG54_IPM_...
Thank you very much for your response.
I have a couple more questions based on your answers:
1. The trees certainly did get sufficient water, however, we never fertilized or mulched them. Do you recommend any fertilizer? We are aware on how to apply mulch properly; we have mulched younger evergreens but never the white pines.
2. What kind of trees do you recommend to plant? We would plant additional trees in other areas of our property where they would have a lot of room to grow. Are spruces and firs good choices? Our soil consists of decomposing slate, drains very well and is very poor in nutrients, with a pH around 6.5.
Again, thanks a lot for your help and we are looking forward to your answers.
Best regards, Susanne Kuehne
We would not recommend fertilizer at this time for two reasons: first, a soil test should be done to see if there are any particular nutrient deficiencies, as often balanced fertilizers contain nutrients not needed (or could create excesses, which is either damaging to roots or polluting in runoff); and second, stressed, diseased, or otherwise ailing plants should not be fertilized until the causal agent is controlled. Fertilizer can stimulate growth which will be either vulnerable to infection/infestation or which the plant's other tissues (especially if compromised from dieback) will not be able to support. Although you mention the soil is poor in nutrients, it would be beneficial to know exactly which nutrients are lacking so they can be replenished, if needed, in a more targeted manner. Information on soil testing and local labs, if needed, is on our page here: https://extension.umd.edu/hgic/topics/soil-testing.
Alternatives to pines are many, depending on your desired use (screening, windbreak, aesthetics), desired mature size, and the site conditions. If fairly sunny and there are no browsing deer to contend with, options include Japanese Cedar (Cryptomeria), Western Arborvitae (Thuja plicata and hybrids), Holly (American - Ilex opaca - or several hybrids), Juniper (several species), and as you mentioned, Spruces (Picea). While Colorado Spruce (Picea pungens) is the most drought-tolerant of the spruces, it has been succumbing to various stress-induced ailments in our area for several years now and would not be a good choice. Better-suited spruces include Norway (P. abies) and Serbian (P. omorika). Firs do appreciate well-drained gritty soils as would be found in mountainous habitat and the somewhat cooler summers that you may get out in Frederick County, but they are still borderline hardy (mostly regarding heat tolerances) in the mid-Atlantic. While there are a few cut-your-own Christmas tree farms that grow fir in Maryland, they are few and the plants need to be monitored for various ailments due to stress. Another, harder-to-find option that appears to grow well in Maryland is the False Arborvitae (Thujopsis dolabrata), which as the name implies, resembles Arborvitae in both shape and foliage. Cedars (Cedrus atlantica and C. deodara) may also work, though their branch spread tends to be greater at maturity than most of the above-mentioned evergreens.
If you wish to try amending the soil to add organic matter (which will aid in the retention of nutrients and water during drought), you can "mulch" the plantings with compost annually. About an inch topdressing will work its way into the soil over time (with freeze/thaw cycles and with organism activity such as ground insects, foraging birds, mole tunneling, etc.).
Thank you very much for your very comprehensive response. I appreciate you taking the time to respond so thoroughly. I will follow your advice and see what happens!