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My citrus tree is not healthy. The leaves are falling off, and the twigs are becoming brown and dying:

dying twigs

In the middle trunk, where a large branch was pruned years ago, there seems to be some burrowing insect that's causing saw dust and what looks like tunnels.

burrowing insect citrus

Also I've been scraping black scale off the citrus and have sprayed with white oil, pyrethrum spray.

Any other ideas about what could be happening? What should I do about it?

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  • How long ago did you first start noticing the branches dying? What did you do around that same time? Fertilize? Where do you live? Are you in spring or summer where this plant resides? I would like to see the base of the trunk of this tree where it meets the soil. Looks like the vascular system has been compromised and only a bit is left to function. The scraping bit is worrisome, the black might just be honey dew, bacteria growing on insect excrement and scraping could ruin the epidermis...don't spray anything else until we sort this out, okay? Check the bark, is it covered with soil?
    – stormy
    Nov 26, 2017 at 4:24
  • Thanks for getting back to me Sue. I guess I noticed it around 2 weeks ago, I haven't done anything different to the plant from usual. It gets slow release fertiliser every couple of months and some seaweed liquid furtiliser now and again. Here's a picture of the base of the plant : i64.tinypic.com/2r7a6tc.jpg It's Spring coming into Summer here. Yup, I'm sure the black stuff was definitely black scale and I have pretty much gotten rid of that but still the green twigs are turning brown :(
    – loginid
    Nov 27, 2017 at 2:34
  • Did you use a magnifying glass/loop to look at the black? Black stuff is usually fracas the poop of the insects...whatever insect problem you have. The reason plants become infested is the plant itself is not happy. Not vigorous. More vulnerable. That major pruning job might have ruined a big chunk of the vascular system...it was cut way too close to the main trunk/stem. Otherwise, need to see the base of your tree and the soil. What soil did you use? Oh, I see the link to your new picture. I'll be back...
    – stormy
    Nov 27, 2017 at 6:03
  • Yup, your tree was buried too deeply. The soil and chips kept the moisture next to the bark long enough for the bacteria to damage the cambium just beneath...the vascular system. Only a third is viable thus the green growth you have left. Pull the soil back until you see the tops of the roots, take a picture. A weak plant is susceptible to disease and insects. Insects are not your problem, the damaged trunk is your problem...hummmm. One more picture? Is this soil potting soil or is this garden soil?
    – stormy
    Nov 27, 2017 at 6:16
  • I will pull the soil back to expose the tops of the roots. The plant has been in this pot for about 3 years now and has been really healthy without any issues apart from at the moment. The pruning was done then. The soil used was good quality potting soil from bags and not garden soil. I'm pretty sure the black stuff was black scale because I identified it from pictures on the Internet.
    – loginid
    Nov 27, 2017 at 22:16

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"Looks like the vascular system has been compromised and only a bit is left to function. The scraping bit is worrisome, the black might just be honey dew, bacteria growing on insect excrement and scraping could ruin the epidermis..."

"Black stuff is usually fracas the poop of the insects...whatever insect problem you have. The reason plants become infested is the plant itself is not happy. Not vigorous. More vulnerable. That major pruning job might have ruined a big chunk of the vascular system...it was cut way too close to the main trunk/stem."

"Yup, your tree was buried too deeply. The soil and chips kept the moisture next to the bark long enough for the bacteria to damage the cambium just beneath...the vascular system. Only a third is viable thus the green growth you have left. Pull the soil back until you see the tops of the roots, take a picture. A weak plant is susceptible to disease and insects. Insects are not your problem, the damaged trunk is your problem..."

"I see no sign of any boring insect. I do see a compromised vascular system. The bark with bacteria and rot would be attractive to boring insects. ... I am so happy that you used potting soil!! Good job! ... The health and vigor of your tree has been compromised by soil and moisture up on your trunk."

"I am almost sure that these 'chewed' portions were after the pruning, during the last 3 years. I don't see sawdust. Sawdust would mean recent damage. That would still not mean the cause of your problem was because of borers, this might be a secondary problem. The dead branches would be good to cut off right at the trunk. I'd love to see what is going on between the trunk and one of those dead branches. Clean pruners with alcohol [before cutting] the end of the dead branch ... off the trunk."

~stormy (from comments)

"I'd suspect too much fertilizer to be the cause. A build-up of excess nitrogen may weaken the plant, and inhibit potassium (potassium strengthens stems and such; too much potassium is bad, too, though)."

~Shule (from comments)

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