Blueberry leaves turning yellow to almost white

inkfinJuly 2, 2014

New shoots of my Austin blueberry are turning from yellow to almost white. Is it Iron Deficiency due to high pH or is it over watering stress, or insufficient nitrogen? Texas temperature has hit above 90F and I have been watering (rain water) everyday. This plant is in a well container having 50:50 peat moss and pine bark mulch. My other blueberry plants do not have this problem, all of them are fertilized with ammonium sulfate as fruitnut and other advised. Any suggestion, advice from blueberry experts will be highly appreciated.

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mhayes8655

Looks pretty green lower down. The lighter stuff may just be new growth that will darken over time

    Bookmark   July 2, 2014 at 11:12PM
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inkfin

soil pH is 4.35, plant getting worst, leaf margin turning almost black. Still can't figure it out what is the problem. Updated picture attached.

    Bookmark   July 17, 2014 at 2:05PM
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fruitnut Z7 4500ft SW TX

That's pretty strange. The dark older leaves gradually turning to chlorotic looking newer leaves I'd associate with excess pH. I haven't seen the blackening later on. Does appear to be a nutrient/pH issue.

They sometimes look like that when the media collapses and waterlogs. But not that much growth. That media should be pretty stable and doesn't appear to have shrunk in volume that much.

It's not your typical nitrogen deficiency symptoms.

    Bookmark   July 17, 2014 at 2:44PM
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ericwi

One way to get a rock solid pH reading would be to water the blueberry shrub with distilled water, and collect some of the excess outflow from the bottom of the pot. This sample can be tested for pH, either with bromocresol green indicator, or with a glass bulb type pH meter that has been calibrated. To my eye, this looks like "iron chlorosis," which would be caused by high pH.

    Bookmark   July 17, 2014 at 4:26PM
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fruitnut Z7 4500ft SW TX

If it's been in the pot long enough that it should have a rootball, pull it out of the pot and see what the roots look like. Are they solid enough to hold the media in a tight ball? Or is the bottom center without roots indicating water logged soil.

    Bookmark   July 17, 2014 at 4:28PM
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inkfin

Eric, I calibrated my glass bulb type pH meter and tested the pH of water squeezed from matrix around and just underneath the root is 4.13 now. However, the pH of outflow of the water collected under the pot is 4.73. Since the matrix is soil-less I don't know if the plant has no available Fe to uptake? Should I add liquid iron or iron sulfate?? What could have caused the marginal chlorosis on the younger leaves? Salt (ammonium sulfate) toxicity?

This post was edited by Inkfin on Fri, Jul 18, 14 at 22:18

    Bookmark   July 18, 2014 at 9:55PM
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fruitnut Z7 4500ft SW TX

Yes add some iron. Sometimes iron chlorosis becomes so severe that the leaves begin to die. That could be what's going on.

Don't expect immediate results. The white leaves won't turn green even if it is just an iron issue. New leaves will be greener.

    Bookmark   July 18, 2014 at 10:36PM
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inkfin

Dr. Winter, about two months ago this plant was in a one gallon pot when I purchased from a local nursery here at Aggieland ;) I transplanted it to this bigger container so I would not expect it would have a huge rootball. Our city water has pH of 8.6 and this nursery was watering all their plants with city water yet the plant was lush green at the time I purchased. It got these new shoots when I brought them home but the new shoots gradually turned pale yellow to almost white on my first picture. Anyway, as you suggested, I pulled out the plant from the pot today, and medium doesn't show water logged sign. What is your opinion?

    Bookmark   July 18, 2014 at 10:38PM
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inkfin

Here is another picture of rootball. Though I have not given up hopes yet the worst case scenario would be I will lose you Austin.

    Bookmark   July 18, 2014 at 10:42PM
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strawchicago 5a IL(zone 5a)

Hi Inkfin: I post in Organic Rose forum, and saw the same problem when the nursery used FRESH PINE bark, at pH 4, as the growing medium for a young rose. The leaves turned almost white. I re-posted what you wrote: " I have been watering (rain water) everyday. This plant is in a well container having 50:50 peat moss and pine bark mulch."

pH of rain water is 5.6, and pH of peat moss is 4. pH of pine bark mulch is lower than 4 when soaked in water. You got an EXTREMELY ACIDIC medium which result in "acid-burns" in your plant. A quick way to fix is to spread pulverized dolomitic lime (has both calcium & magnesium, at pH 9) ... that will balance the pH. Or use your city tap-water at pH 8.6 to correct the extremely-acidic environment.

The good potting soil, the Pro-mix, has peat moss, or composted pine fines (less acidic), plus dolomitic lime (pH 9) and gypsum (neutral pH). See below link for the red-cabbage pH test I did in Organic Rose, which shows how acidic pine bark is. Fresh pine bark is even more acidic than peat moss, when mixed with rain-water.

Optimal pH of blueberries is between 4.5 and 5.5 ... folks in Fig Forum tested pine-bark soaked in water, and it registered much lower than 4, plus killed a few plants.

Here is a link that might be useful: Red-cabbage pH test of many samples

    Bookmark   July 18, 2014 at 10:56PM
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fruitnut Z7 4500ft SW TX

The rootball looks OK. Try the iron sulfate if that's what you have.

    Bookmark   July 18, 2014 at 11:19PM
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strawchicago 5a IL(zone 5a)

I once ordered Iron Sulfate and put them around pale azaleas & rhododendrons ... ended up killing 3 of them. After that was done, I googled on Iron Sulfate and found the warning that it burns roots .. too late.

Iron Sulfate is acidic, will make the situation even worse. My soil pH is 7.7, and my acid-plants were much healthier & bloomed better BEFORE the Iron Sulfate application. So I used the left-over Iron sulfate to kill weeds ... that worked great !!

Iron doesn't work unless it's in a chelated form. Iron sulfate will acidifies, but doesn't help to green up. When the pH drops too low, iron won't be available either.

    Bookmark   July 18, 2014 at 11:28PM
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fruitnut Z7 4500ft SW TX

Strawberryhill could be right about iron sulfate. But burning and pH alteration are highly doseage dependent. Too much of lots of things is bad. I have mostly used iron chelate, expensive but effective. It won't burn

    Bookmark   July 19, 2014 at 12:10AM
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charina(6b)

Since the matrix is soil-less I don't know if the plant has no available Fe to uptake?Am I reading between the lines correctly that you are using a soil less media, but have not fertilized aside from ammonium sulfate?

    Bookmark   July 20, 2014 at 9:47AM
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charina(6b)

Some info about pine bark

"Pine bark should have a natural pH between 4.0 and 5.0, ideal for blueberries. Several sources disagree whether the pH goes up or down slightly with decomposition."

"Low oxygen composting of pine bark (anaerobic respiration) causing very low pH. This can occur in pine bark when mold (mycelia) develops in a band 24 to 30 inches below the surface of the pile. This creates a cap that seals off oxygen. Anaerobic respiration can occur producing acetic acid (vinegar), phenolic and alkaloid compounds toxic to plants. The pH may drop as low as 2.0, which causes nutrients (fertilizer salts) to be flushed from the pine bark. These can also be toxic. Check the pH before planting. If low pH is a problem, wet and aerate the pine bark. After three weeks the pH should return to about 4.0."

Source: http://extension.uga.edu/publications/detail.cfm?number=B1291

    Bookmark   July 20, 2014 at 10:48AM
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inkfin

Strawberryhill, thanks for your invaluable suggestions. I have started watering the plants with city water (pH 8.6) and monitoring the change in substrate and outflow water pH closely and avoided adding iron sulfate. Pine bark substrate I used was not fresh, it was composted bark. I have not measured the pH of pine bark by itself, maybe I will check it within next few days.

Fruitnut, I found a 16 oz bottle liquid iron chelate at the local nursery for $5.40 (w/tax) which I think is not terribly expensive, and I treated the plant as suggested on the label. Hopefully, it will take care of iron chlorosis.

Charina, thanks for the information about pine bark substrate. The link also mentions "High manganese levels" in pine bark substrate. My low substrate pH has not yet shown manganese toxicity sign in the plant leaf yet. I will also closely monitor any appearance of Mn toxicity. I have been fertilizing all of my blueberry plants including this particular one with Miracid (once a month) besides weekly ammounium sulfate as suggested by fruitnut. Another rabbiteye variety I have Climax or any other SHB varieties have not shown any of these symptomps and that is why I was puzzled.

Thank you all for your great suggestions I will post the updates in a month or so as it progresses.

    Bookmark   July 21, 2014 at 11:02PM
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inkfin

Updates
Thanks to everyone for your suggestions and comments. At one point the soil pH alarmingly dropped down under 3.0 but thanks to our city water of pH 8.6 (having 432mg/L bicorbonate) that helped to recover this plant. Though still struggling to adjust/maintain the pH above 4.5 as I might have more than enough sulfur at the beginning. Anyway, here is the current image.

This post was edited by Inkfin on Tue, Sep 16, 14 at 11:55

    Bookmark   September 15, 2014 at 5:11PM
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