I have a potted lemon tree which I was thinking I ought to bring indoors again soon, but discovered that a lot of the leaves have light brown spots on them, which you can scrape off with a thumbnail. I guess it's some kind of insect/pest, how do I get rid of it because I really don't fancy it indoors with these on it?
It may be related as it's been stood on the patio next to a large bay tree which I've noticed over the past month or so seems to have attracted loads of wasp type insects - I don't think they're the type that sting you though. There are also some of these brown patches on the bay leaves but also, all around the bay there is a sort of black soot-like deposit on the patio. I tried to scrub this off with soap & water & a stiff brush at the weekend, but couldn't shift it at all.
Does anyone have any ideas what either or both of these problems might be please?