Some questions about declining Grapefruit tree...

9 years ago

Hello. Recently a friend of mine began renting a property which contains a large grapefruit tree. He has told me (although I didn't see for myself) that a couple months ago it was extremely healthy. Apparently, the previous owners very recently removed what appears to be major limbs off the tree for whatever reason, and he has told me that ever since then the tree appears to be unhealthy. I took a look at it earlier this week, and it did appear to have several problems, and upon closer inspection and taking photos, it looks to have a large infestation of what appear to be some sort of scale or something, and some sort of nutrient deficiency, though I can't figure out what, and was wondering if someone could help me identify these problems and how to fix them. I tried being as descriptive as possible with the photographs to help out.

This is the overall shape of the tree, and it appears that there is some outer twig dieback, though I don't know if that was there before the prune or not:

Here on the base of the trunk, it looks like someone may have recently hit it with a lawnmower or thread trimmer or something. Some of the wounds have begun to heal:

Here is where the majority of the limb removal took place. Elsewhere were signs of just some small branches having been removed:

This is the growth that indicated to me that it has a nutrient deficiency, though I have not much of an idea what:

Here are some of the parts that looked like they had an infestation. I *think* it might be scale, but I'm not sure:

Featured Answer

johnmerr

9 years ago

last modified: 9 years ago

If it is not infected with Greening disease, a good copper/oil spray would help a lot. You have a lot of issues from scale on the limbs, CLM, insect eggs, fungal infections and probably lack of food. If it indeed has Greening disease, it would be best for everyone if you cut it down and burn it; and replace it with a new healthy tree. Oh yes, the large white spots on the trunk are not scale, but lichens; they do no damage; but a copper/oil spray will help control them if you don't like the look.

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Comments (6)

perfectusinfinitusvita
Original Author
9 years ago
These leaves didn't have insects on them, but they did have black spots that look like they either used to, or had some sort of fungus:

The fruit wasn't the most attractive thing in the world, but I opened it and it looked good inside and tasted sweet (actually if anyone could tell me the cultivar that would be really awesome too!):

The ground around the base of the tree had a substantial layer of ashes and charcoal that I guess the owners had put there...Probably not helping with that nutrient deficiency thing lol:

That's it for pictures (I know there's a lot) If anyone can help me advice on with how to get this tree back into good health again, I will be very appreciative!
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Laura LaRosa (7b)
9 years ago
John is very knowledgeable. I can't help as I do not know much about in-ground trees. Best of luck and please let us know how it turns out.
perfectusinfinitusvita
Original Author
9 years ago
I don't really think it's greening, as I tried the fruit and it was sweet and fairly uniform in color, and the chlorosis on the leaves seems pretty symmetrical. I do agree with John as far as the insect, and lack of nutrient problems. I'm not really worried about the lichen, just the wounds. Any possible identification on the insect/fungus/nutrient needs? I do need to figure out why it got into this state in the first place, to help prevent it from happening again, and to build on my botany knowledge base. Also I was thinking of trying to spray it with Imidacloprid, removing all that ash and grass around the trunk, laying down a nice thick layer of pine needle/oak leaf/pine bark mulch, and maybe or maybe not applying a slow release fertilizer around the drip line. Not sure about the fert. though because I dont want to further stress the plant out.
johnmerr
9 years ago
last modified: 9 years ago
For a tree that size and condition, if you are going to apply imidacloprid, it is best applied as a soil drench around the base of the tree and around the dripline. If you are not a professional pesticide license applicator, the imidacloprid you can buy is pretty weak; so I would put a LOT, as in double the label recommendation. Note that Imidacloprid is only an insecticide and will not treat or prevent other problems.
perfectusinfinitusvita
Original Author
9 years ago
After doing a good bit of research, I think I found at least a couple of the main problems with the tree. Reading about symptoms of greening, like asymmetrical mottling, leathery leaves, bitter, half green fruit, and yellow veins makes me pretty confident that it's not that. What I do think I have is probably a manganese or a zinc deficiency. As far as those raised bumps all over... I'm about 90 percent sure now that its because of melanose. I still may or may not have scale, but I'll have to re-investigate to see if that's even a major issue. Tell me what you guys think.