In article ,
david wrote:
Your plant has scale insects, ...and the Pic didn't take long to open.

In which case, spraying won't help. They should be scraped off gently
with a bluntish but pointed knife or similar. Repeat a couple of
times as young ones grow, and they can be dealt with.

I should have remembered that scale insects are easy to see and hard
to notice! Exactly unlike red spider mite.


Regards,
Nick Maclaren.