Citrus Leaves - White ... stuff?

[Viking Guy]

Need help identifying this white stuff.

I installed citrus on my mother's property awhile back, and she sent me these photos wanting to know what this white stuff is.  No, it's not a web.  It is a Rio Red Grapefruit tree.

[stormin]

Looks like powdery mildew to me.

[Viking Guy]

She says it appeared right after a mild rain.

[simon_grow]

looks kinda like residue or hard water to me.  Dried up rain water should be clear.  Do you have sprinklers near by or have you used a foliar spray recently?

Simon

[Rtreid]

Was that the first rain in a while?  It looks like dust that has washed off the leaves and collected in the upturned leaves that are able to trap water. I see this after a rain with my citrus.


Richard

[Viking Guy]

She said she has been without rain for awhile.  Dust and dried foliar spray rinsed down sounds right to me.