I had one of my blood orange trees get real sick on me all of a sudden. It had been in a pot and I had it outside after being indoors all winter to get some sun for a few days. It started looking bad, and I found out that ANTS were killing it! Have you checked to see if maybe there are insects that are bothering the root system? This is just one thing to think of, other than too much or not enough fertilizer.

Have you checked for aphids? Ants farm aphids.

You wrote: "the leaves look fine which is strange."

Um. What leaves? The branch in the picture should be full of them.

I'd also check for scale..if your citrus has ants it could be due to insects..aphids and scale are most common.
Inspect leaves, underside, upper, stems. Feel for stickiness on leaves..let us know what u come up with.
Toom, like Jean states, what leaves? I only saw a few..or perhaps it's just the one branch that's lacking foliage. Toni

thanks to all for the replies and they all help.

thought i'd replied to this yesterday!

there are ants around where we live but none that i can see near the tree itself. is there a particluar place i shoudl look?

regarding the leaves i should correct what i said. the leaves did all fall off but now they are growing back on many branches and look healthy with no sign of stickiness.

the most noticable problem is that all the flowers died and then the stem inside turned black. so when the flowers dropped off there was a little black stem, which just falls off too. this and the end of some branches being black worries me.

Toom, so the plant itself doesn't have ants on it? Well, that's good news.
In the meantime, I'd check for pests..and be sure not to overwater soil.
Cut off the black stems..
Since your tree is putting out new foliage, let's hope it's okay..
BTW, do you fertilize? If so, what do you use? Never overfeed a plant.
Keep us posted on its progress..Toni

thanks again for the reply.

all the black ends have been cut and it looks better. do you mean feed by fertilize? i have some plant food which seems to be for everything under the sun which i use but should i have something specific for citrus trees? and how often should i use it?

Toom, yep, when I say feed I mean fertilize. Sorry about that..The best fertilizer is Citrus or, if you can't find that, Azalea.
I don't want to tell you when to feed because all fertilizers differ..some are meant to use every 3 months, others a few times a yr. They all differ. It's important to read container directions. It describes the correct amount to use and feeding times. BTW, don't buy spikes..they're awful..Pellets/granuals are my favorite..just sprinkle on soil then water. There's no mixing involved, which means less work. LOL..
Hopefully new growth will appear on tips you removed..Toni