Problems with Boxwood - Knowledgebase Question

University Park, MD
Question by LynnHButler
June 23, 2006
Hello. I transplanted 6 boxwoods (about 4ft)last fall around a new patio. They did great all winter and had wonderful new growth this spring. However, I noticed this week on a few of them that the leaves are turning yellow and underside are a few round brown spots about 4 spots per leave and they are very specific looking spots. What could be the problem and what can I do?

The shrubs are in pretty much full sun. How much water requirment do they need and should I fertilize them? I've had the shrubs for about 4 years and have had no problems thus far.

Thank you, Lynn


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Answer from NGA
June 23, 2006

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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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