Twig blight (blueberries)

I planted these blueberries at the first week of April and irrigated till first week of July with 5.5 ph water only… (the substrate being 40% peat %30 pinebark %30 perlite)

On 9th of July I started fertigation. 3 weeks of 0,30 gr N per week for July. And for the first 2 weeks of August 0,50 gr N per week.

K,P and other minerals accordingly…

The interesting thing is that the response of Darrow and Duke (especially Darrow) has been very negative to this fertigation at each week whereas of Patriot Chandler and Bluecrop very positive…

What do you think the reason might be…

When I search at internet for twig blight (at Darrow below) there are comments about a fungi causing that…

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What form of nitrogen? What is the current pH?

%40 urea, %40 NH4, %20 NO3. I ll re-measure the pH for each and write …

NH4 is going to make the mix more acidic and it is already there with the composition you’re using for soil. And the NO3 I assume is a nitrate, which blueberries can only absorb a limited amount. Too much will kill the plant, eliminate it. Blueberries have limited receptors to process, and when they get too much they overdose and die. The urea is only slightly acidic and is your best option. I add ammonium nitrate only once a year. And if you added sulfur, well that could make it too low too. For micros and stuff I use Holly-tone once a month.

If your soil turns out to be below 4.0 just flush it for 5 minutes with tap water (not rainwater). That should help rasie it back up. It’s easy to go too low in containers. I killed a couple that way!


I was thinking ammonium sulfate, as acidic I don’t think ammonium nitrate is acidic. But it is a powerful nitrate so should not be used. I put the sulfate on potted plants once a year, not nitrate.

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Andrew, I measured yestersay each each pots soil pH with Hanna probe. there is nothing wrong. all around 4.80-5.5…

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I will measure the soil EC as well and share…

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Ok what that is great. Avoid nitrates. Are these to stay outside during the winter? You are in a fairly mild zone, I would probably wind down fertilizer now. I myself stop August 1st. Maybe they got a little too much? Or you do have a blight problem. Usually occurs early in spring, but can anytime. Remove a stem that contains both dead and green leaves and split it lengthwise. If you find a light brown line down one side of the inside of the stem, suspect stem blight.

Thank you very much Andrew. I ll do that. I have read that one can give fertilizer up to 6 weeks before the first frost… In this area first frost date is around end of October.

I also measured the salinity of the soil. There is nothing unusual.

I ll take 2 measures: In order to avoid nutrient leaching I did not irrigate with normal water after fertigation because I was irrigating almost everyday…I will not do that anymore and start irrigation to a small extent after fertigation.

And secondly I will decrease the weekly N ratio by half because other varieties literally “freaked out” with the current amount.

I think and hope these will help…

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Speaking of blueberries I had a great year. Most I ever harvested. I still have 4 plants that have some berries. I have been harvesting for about 2 months now. I have 9 plants.
Here Ka-Bluey, it’s an early ripener, and is long done. It continues to grow like a beast

Chandler is 5 feet high and 5 feet wide. It is still producing and will for a couple more weeks.