All,

I'm new to this gardening game, but bear with me. We have a plum tree
that's not too well. According to the arborists who have come to have
a look, we have black knot, aphids and something that does leaf cutting
(ants?). Now, both people who came out recommended pruning out the
black knot, which is okay with me. However, person A said that they
would use an insecticide and a fungicide to get rid of the aphid and
leaf cutter problem and then fertilise the tree, whereas person B said
that they would just fertilise and would not spray.

Now, my question is this, will fertilising alone invigorate the tree
enough so that it'll recover next year? i.e. come back with a
vengence. Or is it better to spray the tree now and then spray again
and again each year? Incidentally, the plum tree is (on their
estimates) approx 30 yrs old, so it must be relatively hardy? and we
are apparently in Zone 43 in Canada, if that helps?

I know it's hard to give advice without seeing the tree, but I guess
i'm really asking whether or not the aphid and leaf cutter problem will
always be there and one should just fertilise and let the tree look
after itself!

cheers

col