Thank you very much for your answer. I know you are right for the soil analysis, but I,m not in the US, I'm in Roumania, Europe and I don't really know where to do it, but I'll look it up. The soil is not sandy (it is muched with sawdust), and the garden was cultivated with potatoes until a few years ago. Since then it was used only as a pasture for hay. Until now humidity cannot be the problem, because my ph-metre does also humidity analysis and it always showed wet. I put another photo with the blueberries and the region.

Here is another photo of a bluecrop.

Is it my imagination, or does that weed leaf on the ground right below your thumb in the first photo also show some red pigmentation? That weed, and your bluecrop look like phosphorus deficiency causing anthocyanin pigment buildup. That can be caused by cool soils, or a deficiency in the soil. The newer leaf margins on your bluecrop look like typical P deficiency due to cool weather.

Do you know how much calcium was in the fertilizer? Excessive calcium can compete with the Mg (even if you applied Mg, it may not be available to the plant), and without adequate Mg, P cannot be utilized.

In your first photo, are those leaves that have turned red newer or older leaves? I can't tell for sure if that is the top of the plant, or an older lower section. I ask because Mg deficiencies often show up in older leaves prior to newer leaves.

To charina:
Thank you for your answer.
It is not your imagination, some of the weeds are realy red, and not only them but also the leaves of the very young trees in the forest are also red. The weather was indeed cold (4 degrees C during the night, several nights, and a lot of fog from 2 am to 9 am), but this is the usual weather in this region, although it got a little warmer in the last years.
The fertilizer did not contain calcium at all (Florovit special for blueberries, made in Poland).
In the first photo there is in fact a 1 year old Bonus and the red leaves are those from the top, so the newer.
In the third photo there is a 2 year old bluecrop.

You may have a few issues going on. The photo of the bluecrop looks like P from cool weather. However, that first photo is not typical of cool weather P problems. That is more strongly interveinal than would be typical. So, it could be that that plant(s) have something else going on - acute Mg deficiency?

The three Bluecrops dropping all their leaves probably is something else all together. Transplant shock and/or failure to establish? Or did they show red leaves like the first photo? Have you looked at photos online of blueberry shock virus? Photos I have seen look a bit different (varies depending on varient of virus infection) than your plant, but it does look somewhat like some virus infections.

I don't know anything about how to answer your question, but that photo is lovely! What a beautiful region.

The leaves on my blueberry plants regularly turn red as Winter sets in. I don't know anything about whether that is good or bad.

Was the conifer sawdust that you use fresh, aged, or composted? Sawdust, especially fresh, can strongly affect what nutrients are available to your plants.

I used aged sawdust with my blues, and I had to apply extra ammonium sulfate to get them going. Red leaves shouldn't be a symptom of N shortage though.

ali400,
I am not any expert in this field but your blueberry seems like it has Magnesium (Mg) deficiency as this website below indicated magnesium deficiency often happens in sandy soil like yours.

Here is a link that might be useful: Magnesium Deficiency

To Charina: I've attached one photo of a Legacy that has started to drop some of the leaves 5 days ago to see how the 3 bluecrop that lost all their leaves looked like. It is in the pot that it came from the nursery because at first I thought Ioverfertilized it and I wanted to get it out, wash it and see how the roots looked like. They seemed fine.
However, only the 10 bonus and 2 bluecrop have red leaves (like scorch virus infection, although the nursery gave me a virus free certificate), almost half of the bluecrop are looking like the one in the third photo (that you suspect P deficiency.
Should I destroy the 12 plants that are virus aspect?

To daisyjoy5: Thank you. Come and visit. There are also a lot of mineral springs water where you can drink for free at your good will.

To northernmn: the sawdust was fresh because the nursery told me that if is conifers sawdust I can use it fresh.

To Inkfin: the soil is more clay then sandy and I thought that if I fertilize them with a fertilizer that included Mg they couldn't be in such deficiency.

I would contact someone at the N. Balcescu, Agronomic College Bucharest. They should be able to help you get the soil and plant analysis.

Thank you very much for the idea. You are very kind. I'll call them first thing tomorrow.

Notice how that legacy in the photo is showing chlorosis. The leaf veins are darker than the interveinal leaf tissue, which is yellower than healthy plant tissue. Generally that means an iron deficiency (most likely caused by high pH), but Mg deficiency can do the same thing - albeit usually starting on older leaves whereas a Fe deficiency tends to be the whole plant, or newer leaves. The photos I have seen of Mg deficiencies in bbâÂÂs are quite variable. Then, the red color still could be either the cooler weather impacting P availability, or an additional symptom of Mg deficiency. The plant is already stressed/struggling even before the stress of transplanting.

DonâÂÂt destroy any plants based on my commentary! I have limited practical experience with bbâÂÂs, and have never dealt with a virus issue myself. IâÂÂve simply done a lot of reading, and am trying to provide possible suggestions to investigate.

One source that I refer to often is Spectrum Analyticsâ document on fertilizing blueberries. See Spectrum Analytic Inc. FERTILIZING BLUEBERRIES The photo on page 24 is the closest I have seen to your plantâÂÂs red, other than some virus photos (e.g. cornell) I would suggest reading there about P and Mg, along with all the other good info, if you havenâÂÂt already.

You fertilized with a fertilized that included Mg . . . but what is your native soil like? Could it already have been Mg deficient? High in K or Ca that could make the Mg less available? (seems plausible if your region has natural mineral springs). Plus, it appears, based on the potted plant, there may have been preexisting issues - perhaps with Mg.

BlueberryHillsFarm had the best suggestion right at the beginning. A leaf and soil analysis is in order. Otherwise, itâÂÂs just guesses and testing to see what various treatments might do. Even so, were it me, I might try a test on one or two plants by applying espom salts to provide additional Mg. 1/4 cup evenly distributed in a 10-inch diameter circle around the plant. (source for application recommendation). When I recently suspected a Mg deficiency in a couple plants, I added 1 Tbs per gallon of water and wetted the root zone. Results are yet to be determined.

DonâÂÂt forget, the fresh sawdust will tie up nitrogen in itâÂÂs decomposition. You may need to add more nitrogen than normal to compensate for this.

You are right that the soil might have been deficient in P and K because it was cultivated with potatoes which I read today that are big P and K eaters.
We will try to do the soil analysis.
Thanks.

I agree, the photo of the farm was beautiful indeed! I am most impressed with the blueberry expertise on this forum.

ali400,
BlueberryHillsFarm, Charina, and all others provided you the best solutions and expert advises. I have also found a few other websites listed here that provide some information on blueberry diseases as well and maybe helpful to know:
http://mtngrv.missouristate.edu/assets/commercial/BlueSchilderOverviewBlueberryDisease101912.pdf
http://blueberries.msu.edu/uploads/files/Scorch.pdf
http://www.ncipmc.org/alerts/blueberry_scorch.pdf

I took in touch with someone to perform the soil tests.
However, I read the pdf from the missouristate.edu, that Inkfin recommended, and all the symptoms that my blueberries showed (red, brown, yellowing and lost leaves) are, as everyone suggested it, a sign of Mg deficiency.
I bought Epsom salt and I will apply to those showing symptoms, see what will happen and wait for the tests results. Thank you very much to everyone and I'll keep you in touch.

Please do post a follow up report when you get more information. I'm very interested in the outcome.

Hello everybody,

I've just got the soil tests results.
First of all, the soil sample was took from the area between the rows which was not fertilized, as we only fertilized the plants, and we have two and a half meters between the rows. Here are the results:
N good,
P low,
K moderate,
Ca low,
Mg low.
We added Epsom salt for all the plants and a little bit of ammonium sulphate (the last one in a very large circle of about 20 inches diameter around the plant).
We also spoke with a horticulturist and he suggested a fungal infection (we also observed signs of spotted leaves on some of the bushes), so we treated them with a fungicide and an insecticide (aphides began to appear after the warm, rainy days).
However, we've got good news. The bbs are doing better, their leaves, generally, got a lot greener and they began to produce new leaves.
The 3 bluecrops that lost all their leaves appear to be dead, but the legacy that you saw in the last photo is much better, greener, and has new little leaves growing.
The ones that appear to recover very slow are the 1 year old bonus (first picture), but we only have 10 of these, so even if we will loose 5 (which we think we will), there is no drama. First when we planted bbs we wanted only 3 year old plants, because we thought the bigger the plant and the pot it comes in, the bigger the chances of survival, and we were right. As you can see the 1 year old bushes are more sensitive, then comes the 2 year old and the 3 year old are much stronger.
Fortunately, the big majority of them is doing much better and this is the most important.
We want to thank everybody again for their advices and we'll keep in touch on the forum.

phosphorus deficiency.

phytotoxicity with aluminium from soil, probably