What is causing white patches on the underside of my bamboo palm?

Question

I have a bamboo palm, which when i first bought was infested with mealy bugs. Over a period of two months I have regularly used rubbing alcohol to reduced the infestation as much as possible. And now it is very hard to find one, sometimes I have to really search in the nooks and crannies .

Now that the bugs are almost gone I have started paying attention to the white patches found on the underside of the leaves (picture below). At first i thought it was because of the mealy bugs but since they are almost gone I think there might be another reason. I was hoping if someone can help me identify the cause for these patches? (they look like water stains, pretty flat)

Answer 1

They are either pesticide residue from when it was sprayed in the growers greenhouse or, most likely, hard water deposits that are typically seen in areas where the tap water is sourced from areas with limestone that is rich in calcium or magnesium.

They are not harmful to the plant and can be removed by:

• making a mixture of half water and half white vinegar.
• take a cloth and wet it in the solution,
• wipe the leaves
• wipe the leaves again with a cloth soaked in 100% water or give the plant a shower to remove the vinegar solution
• repeat if necessary