Answer: What you describe sounds like a fungal infection (Macrophoma or Volutella) Both are considered to be stress-related pathogens. These leaf spots and blights often occur on boxwood in early spring, and I suspect these pathogens may be dependent on stress (in this case winter time stresses or transplant stress) in order for plants to be weakened and thereby more susceptible to infection. I'd physically remove the affected leaves to stop the spread of the disease and avoid overhead watering for the same reason. Boxwoods need well-draining soils and about one-inch of water per week. The easiest way to water them is to build a watering well or watering basin beneath each plant and flood the basin; allow to drain, then flood a second time. This will concentrate water over the rootmass and allow it to trickle down and wet the entire root area. I wouldn't fertilize them now because they are under stress. Boxwoods typically don't need to be fed regularly but next spring (by then they should have recovered), you can side-dress them with a slow-release all-purpose garden fertilizer. Best wishes with your boxwoods.
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