Mysterious blueberry disease

Asked April 1, 2020, 3:52 PM EDT

I have a blueberry plant with a disease I cannot identify. Plants are being grown in pots with a combination of RAC, peat, and bagged organic compost. They were fertilized with 1/2 cup of Ammonium sulfate about 3 week ago, and there were no signs of disease at the time. Also, when plants were fertilized they were also lifted and more RAC was placed in the bottom to return soil level to proper height. Plants are about 10 years old. My first thought was scorch disease but I could find any evidence that it is occurring in California. Also thought about twig blight?

Santa Clara County California

1 Response

Well that does not look like any disease I recognize. Black stems are very unusual. We see black stems from bacterial canker but that is a disease of a cold wet spring and I doubt you have that. Fungal diseases usually cause the stems to wilt and turn brown.
I also see black stems when a grower applies too much fertilizer and burns the roots. This causes a distinct wilting and dieback. The roots will die and the leaves will burn brown and fall off I see burnt leaves shriveled and dead black and brown stems that look consistent with fertilizer burn. I suspect when you stirred up the soil, adding soil and fertilizer, the soil solution was too salty and the roots died. If the plant was healthy before and declined after I would think it was something you did rather than a disease.
The fact that you have new shoot growth coming is a good sign indicating the plant has but out new roots and is absorbing water again and putting out new leaves. We probably watered pretty heavily and that would have diluted the salty fertilizer solution. Let me know if you have more questions.