White Powdery Coating on Bay Plant
Answered by: Conrad Richter
Question from: Alexander Mckee
Posted on: August 02, 2007

I ordered three bay laurel plants (along with some other plants). Everything else looked fantastic and I was completely satisfied. The bay plants, however, all have a strange powdery coating on most of the leaves. I have tried to wipe this stuff off but it just seems to return.

We use soap sprays for insect control on our plants and these do accumulate as a sticky film on older leaves of some herbs, most noticeably on bay. When you wet the leaves the moisture darkens the white marks but when the leaves dry the marks come back. A little very gentle washing helps to remove the scum partially at least. In our experience those lower leaves eventually drop as they are replaced by newer leaves as the plant grows. Because bay is a slow grower it may seem like ages before the marked leaves disappear -- perhaps as long as 2-3 years.

Mildew is another possibility for the white coating. This is a fungus that attacks a lot of different plants. Treatment involves anti-fungals such as sulphur spray. But our experience suggests that the much more likely possibility is soap scum. A key test is to look at any new leaves: do they also have the same white marks? If not then you likely do not have a mildew problem.

I bought these plants with the intent of using the leaves in cooking but I’m not sure if I would be comfortable eating them. Any research I have done suggests that this white, powdery coating is likely a fungus. If this is true then what is your policy?

If the problem is soap residue washing the leaves prior to use should be fine. The soap we use is safer than most dish detergents. If the problem is mildew then we will replace or refund the plants depending on what is practical.

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