The rosemary plant in my kitchen has developed a white powdery residue on the leaves and stems. What is that?

It could actually be aphids. woolly aphids look like "white stuff" on a plant. Look close, and blow on it - does anything move? If so, the best thing to to is remove them. squish the little buggers, and wash the plant.





If the residue is powery and very thin, it could be powery mildew. In which case, it's harder to treat. It's especially hard to control indoors. And once it appears, you can't fix it - only prevent its spread. Remove the affected parts, if it's only a little bit, and try to improve the conditions. Good air circulation is important - difficult to acheive indoors. You can also spray the plant with 1/2milk-1/2 water in a spray bottle. It will change the ph on the surface of the plant to a level that powery mildew doesn't like.





Again, most treatments (if it's powdery mildew) are preventative - not cures. But it shouldn't kill your plant outright.





When it gets warm, plant it outside and cut it back, and it should spring back just fine.

The rosemary plant in my kitchen has developed a white powdery residue on the leaves and stems. What is that?
Powdery mildew, aphids or mealy bugs.


Being an indoor palnt I'll asume it is still small? Stuff paper or foil in balls around the stem of your plant, to hold the soil in the pot. Then fill sink with warm dish soapy water and swish plant back and forth - gently rubbing areas that are affected. Be sure the plant dries - daub with paper towels - to prevent more mold or mildew.


BTW: Never spray milk on your plants as it clogs up the "pores" and can cause a bad case of mold or mildew.
Reply:strange, and I have actually proven that the milk sprayed on the powery mildrew actually kills the fungus..and is a good thing..
Reply:Most likely it is powdery mildew. I have had some luck with milk also, but your best bet is to remove it from the house or it will spread. Prevent this in the future by making sure you wash the pot you are planting in with warm soapy water and spray with a disinfectant like lysol prior to planting. Also make sure you are not overwatering. Too much moisture (like on a ledge over the kitchen sink) will set your plant up for this.
Reply:lime.Mildew.