brown branches on rio red

whiskers222April 28, 2012

I have a rio red grapefruit tree that has been in the ground about two years. This past season I had a lot of grapefruits on the tree. I know the tree suffers from citrus leaf minor which I use a monterey garden with spinosad spray and some volk oil that I heard about on this forum. My question is why are some of the branches losing their leaves and turning brown? I wanted to post some pics I have but I am not sure how to in this message. thanks in advance.

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Limb die-back has many causes. If you have alkaline soil or water and your tree is on a P. trifoliata (or one of its hybrids) rootstock, it is normal. It also can occur when you over fertilize with nitrogen. Several fungal diseases also cause this. Some scion varieties are more prone to this than others, but Rio Red is usually not a problem. Just one limb can be ignored but if there are more, I would suspect root damage.

    Bookmark   April 29, 2012 at 2:18PM
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Thank you for your response.

    Bookmark   April 29, 2012 at 4:16PM
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pgde(Tucson Zone 9)

Hey Tantanman: I seem to be having the same problem with my Rio Red. How does one fix root damage? Or do I need to start over? My other 6 citrus trees are doing fine. See below pix.

Thanks so much!


    Bookmark   April 29, 2012 at 4:50PM
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Yes that is what my limbs look like in that picture that pgde posted. I would say about 10% of the limbs are like that. Do I cut off the brown limbs or will they grow back?

    Bookmark   April 29, 2012 at 5:25PM
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When I said alkaline + trifoliate = normal, I should have added (normally) bad. And that leads to poor trees. They just don't like pH over 7.

In Peter's case, I see a lot of white rock. White rock usually means limestone, calcium carbonate. Water percolating down through limestone can get too high in pH. Peter you need to find what that rocks are and what your rootstock is. Most Arizona posters here have said their trees are on trifoliate or a trifoliate hybrid. Trifoliate rootstock needs some shade (mulch). P. trifoliata comes from China and grows as an understory tree in a temperate climate, not near as hot as this. In Tucson you really need 2-3 inches of pine or fir bark mulch for insulation from the sun. Do not use hardwood mulch as it will add even more calcium. I would try the mulch. And if the rock is limestone and it is mixed in your soil in small pieces you may need to acidify and or make a slightly raised bed. Bear in mind a raised bed is more difficult to keep cool in the long hot summer. I don't like bark mulch except in this kind of service. Later on when the canopy fills out and shades the roots, you can do without it.

    Bookmark   April 29, 2012 at 6:29PM
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pgde(Tucson Zone 9)


Sorry for the delay in responding. The rocks are camera overexposed non-limestone (sandstone, etc). While, fortunately, this side of Tucson does not have caliche, we do have high pH soil here (8.0-8.2) which is typical of desert soils. When it was planted, a good amount of sulfur was added in the hole to lower the pH. Last week I added an amount called for by the gardens sulfur calculator (see link below) and watered it in well. Am waiting for a while to check the pH with my meter. I have also added between 3-4" of bark mulch to the well I had created. I have increased water delivery (drip, 3 gal/hr, 3 hours) to twice a week. Finally, I have been using "Arizona's Best Citrus Fertilizer" supplemented by additional iron, zinc and minors. At this point, I guess I will need to wait and see what happens. BTW, I haven't a clue what the rootstock is. Will need to check around....



Here is a link that might be useful: Garden Sulfur Calculator

    Bookmark   May 2, 2012 at 1:24PM
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    Bookmark   May 5, 2012 at 3:12PM
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    Bookmark   May 5, 2012 at 3:19PM
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    Bookmark   May 5, 2012 at 3:21PM
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    Bookmark   May 5, 2012 at 3:23PM
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I have the same branch problem. Were you able to determine if you should trim them?

    Bookmark   May 21, 2012 at 11:29PM
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