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Patricia Asked

Thank you so much for responding to my question about the Mohawk viburnum. You mentioned a sulfur spray: is that the same as lime sulfur? When is it safe to spray and can I spray the viburnum or is it too late since they have foliage? Is there a safer, more natural way to control a botyris fungus problem? I have another problem in my landscaping plants. Last year I lost a blue moss cypress. It started turning brown then 80% was brown. I sprayed it with Diazinon Plus this fall and it seemed to arrest the damage. However, now my emerald arbovitae is showing brown leaf dieback. Could it be a similar problem? It appeared last year in a small area and we talked to a horticulturist who thought it was environmental but now the dieback is increasing. What do you recommend to spray on arbovitae?

The Gardener’s Answer

Hello again, Patricia: I mentioned the sulfur spray because it can potentially damage the foliage on your viburnums. I apologize, I should have been more clear. I do not recommend spraying this or lime sulfur on your shrubs. Both products can be effective fungicides but should not be used on evergreens or semi-evergreens. The best organic control is good sanitation practices as I mentioned before, as well as making sure the viburnums are planted in an ideal location and have good air circulation. Again, I cannot be certain that botrytis is the problem so you should take a sample to your County Cooperative Extension Service before treating the problem. If we do not know what we are dealing with and we just spray for the sake of spraying, it can do more harm than good, so it is always a good idea to know what we are dealing with so we can treat properly. Spraying is not always the answer. You mentioned that you sprayed your cypress with Diazinon? As of December 2004, this product has been deemed by the Environmental Protection Agency as unlawful to sell as a residential insecticide. It is very toxic and should be disposed of properly; visit the following Web site for more information:
. If your arborvitae is located in an area where you have sprayed, it is possible that the product traveled by wind to your arborvitae and has caused damage. However, it is normal for arborvitae to have some browning on the inner foliage this time of year. If this is the case, not to worry, it is just the plant’s way of making more making more room to grow. Otherwise take a sample of your arborvitae as well as your viburnum to the Extension office.

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