My vanda just bloomed a week ago & I noticed yellow spots on the lower leaves. It has been outdoors for 4 months in SW florida, could it be fungal? If so how do you treat it?
Look on the back side of the leaf... Scale does this. (It is not the only thing that does, but it's the first thing I'd think of) If you see white stuff on the back of the leaf, spray with soap solution, clean it off, then spray with your pesticide of choice (I like Bayer's 3-in-1, but others work fine too)
Anything that injures the leaf can lead to spots like that, especially in humid areas. Scale and mealybugs certainly do it. Other sucking insects can, as well. Other kinds of insects may bite and leave.
There is a lot of information by Motes Orchids on growing Vandas in Florida. Check out their Web site and videos on YouTube.
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