Answer: Sweet viburnum is usually disease free but the frosty weather may have stressed them enough to be attractive to insect pests. Check for aphids or scale insects so you can eliminate those pests as problems. If you find aphids, insecticidal soap will control them; scale insects can be suffocated with applications of horticultural oil. The middles of your plants will thin out unless you force growth with annual pruning. Shearing your hedges will promote healthy new growth at the tips of the branches but will also force growth towards the center of the plant. If pruning doesn't help and your shrubs do not have insect pests, there may be a problem with root rot. Dig down near the roots and inspect both the soil and the root system. Snap a few small roots and look inside. Healthy roots will be creamy white inside; dead or dying roots will be brown or rusty colored inside. Hope this information helps you determine just what is happening with your viburnums so you can take corrective actions. Best wishes with your landscape!
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