Despite their continued popularity in landscaping, spruces are not well-adapted to our Maryland growing conditions. Occasional droughts stress them, as does our high heat and humidity. Planting locations with poor drainage can also cause root dieback that leads to foliage browning or shedding.

It's hard to determine the exact cause of decline from the photos, but depending on how or if they were watered last year during the significant drought, they likely became too stressed and lost roots to under-watering, which then predisposed them to additional stresses this year that they could not tolerate. Over-watering is also a possibility (the foliage symptoms would look about the same between the two), though you can check the roots by tugging on them to see what condition they're in. Roots that succumbed to root rot usually pull apart fairly easily with a mushy outer layer separating from a stringy inner core. In comparison, roots are are alive or which died from other causes take more force to break and tend to snap cleanly in two.

Spruce spider mites are only active in the cooler weather of spring and fall; even though their feeding damage becomes most apparent in summer when it gets hot, the mites are not active at that time and probably would not be detected by a "tap test" (knocking them onto a piece of paper where they'd be easier to see). Spruce spider mites don't make nearly as much webbing as summer-active spider mites on other plants, so the lack of webbing alone isn't a reliable indicator of their presence/absence. The pictured dieback looks too extensive to be due to mite damage unless it built up over several seasons.

There are some foliage infections (fungal needle cast diseases) that spruces can contract here in the mid-Atlantic, but that tends to result in leaf shedding more so than browning. Cankers from those infections can kill branches, but would be unlikely to kill large portions of the plant all at once, though we can't rule it out as an overlapping issue. Fungicide will not cure existing infections if they are present.

We do not recommend replacing these shrubs with more Dwarf Alberta Spruce. If your client prefers having a pyramidal-shaped evergreen in those locations, another species can be used instead, depending on the site conditions (sun/shade, soil drainage, deer browsing risk, mature size space, etc.). Even though the other spruces seem to be doing fine, they may be less stressed just enough to avoid dieback due to nuanced differences in their exposure to sun and heat, soil moisture and drainage, and other environmental factors. If the same species of plant fails to do well in a given location for 2-3 attempts at growing it there, it's best to switch to another species because something in that spot is not allowing it to thrive.

Miri

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