I acquired a black pine about 6 months ago I initially did some decandleling and some pruning and wiring. I've then left over the last 5 months during the summer to just let it rest and grow and see what happens next Spring. Over the last few days the needles have started turning Brown and I don't know whether it's due to lack of fertilizer or whether it's been over Or underwater. I did apply some conifer fertilizer just after I got it.

This plant looks dead. It also looks dry. Several of the branches are dead, including the top, what little green there is is unlikely to sustain the tree. You don't say what country you are in, and unless you took it in to take pictures it should be outside. Water it place it in some shade, cut the dead branches off and hope. No fertiliser and do not re pot.

I'm in the US zone 9 and It's always been outside. It was looking fine until just a few days ago. In fact there was a new green shoot at the very top of the tree a week ago.

Hello, a tree doesn't fade like that for lack of fertilizer (It could happen because too much chemical fertilizer tho), but it does like you underwater it at some point, maybe a heatwave? I know very little about Black Pines, but I think they're more suitable to colder environments...

Maybe it can still recover, I second Geoff about the procedures.

The tips looks like they are still green. In authum JBP loose all 3 years old needles naturally. I agree it looks bad in this case. But it can be that it has been heavily decandled the last two years and that the green you see is the only needles left that are one and two years old.

I would not give up on this tree as it may just be part of the natural growth habit for the species.

mine have never lost that amount of needles, I have several and they are not losing the old needles yet and we have a hot dry summer. I wonder if it got very dry at some point recently.

Not mine as well. But the amount of lost needles is the same amount that was grown three years ago. If it had a good growing season that year and been decandled hard after that, It could still be a possible cause.

Yes, I agree that it is quite possible it dried out at some point. That would also explain the early shedding if it is the normal anual shedding.