Hello, I'm a beginner blueberry grower in Slovenia(Europe) and have what I...

Asked July 24, 2016, 4:01 PM EDT

Hello, I'm a beginner blueberry grower in Slovenia(Europe) and have what I was told a Phomopsis problem. The disease is producing a ring of brown bark at a few inches above the base of stems in a few bushes. I was told to cut out the infected stems as near to the crown as possible and burn the infected twigs until fall when most of the leaves fall off, then heavy spray the bushes with copper hidroxide. It's now mid-summer(July). Are there any other measures that I could use now to minimize the rate of infection, perhaps a light fungicide that can be applied to the bushes or something similar? Thank you, Matic

Outside United States

5 Responses

Dear Matic,

I am not sure it is Phomopsis since we usually don't see a ring around the stem close to soil level with that disease. It looks more like fertilizer, herbicide or other chemical burn. Or was there anything else around the trunk that could have conttributed to this? Are any canes dying? Just in case it is Phomopsis, you are taking the right measures, I don't think a fungicide would help at this point, but the most effective fungicides against Phomopsis are sterol inhibitors (e.g., propiconazole) and Pristine (pyraclostrobin + fenhexamid). Aliette (fosetyl-Al) or similar fungicides also have activity. Best of luck.

Thank you for the reply, Annemiek!

I have had it verified that it is Phomopsis amygdali(constriction canker) and as I couldn't find propiconazole at the time used Indar(fenbuconazole) three weeks ago. It suppressed it for a while, but now it seems to be active again. It's even on some of the stronger and more hardened bushes, as the canes are starting to dry up, but I couldn't see the canker ring as the bark is already hardened. Now I found propiconazole, but we do not have Pristine, we only have separate pyraclostrobin(BUMPER 25 EC) and fenhexamid(TELDOR PLUS) fungicides. I really do not want to lose any more bushes, can you please suggest what course should I take now? Should I spray with propiconazole or maybe combine the pyraclostrobin and fenhexamid fungicides and spray with that? Thank you, Matic

Hello again, I was advised by my local agricultural office, that as you mentioned before, nothing can be done to root out the canker, just moniter and cut out any infected stems as they are found and that I should only apply captan as a protective measure and wait for fall to apply a 10x dose of copper hydroxide. Is this a sound plan? Matic

Dear Matic,
My apologies for the late reply - I have been very busy. I have never heard of Phomopsis amydali infecting blueberry and there is no record of constriction canker (only in peaches). However, it is difficult to rule that out, since I cannot do a diagnostic lab test to confirm. They may have isolated Phomopsis from the tissues, but could have been present internally anyway or entered a wound caused by fertilizer burn. I showed the picture to our diagnostician and she mentioned and she was wondering if conifer mulch might be an issue as there are some Phomopsis species that infect spruce in Michigan. In any case, your best management is to cut out dead and dying canes during dry weather to prevent wound infections - cut to the base of the cane. Burn them or chop them up and bury or compost them. The apply a copper hydroxide dormant spray in the fall and again the spring. Pyraclostrobin and Indar would work as preventatives but not Elevate. The question is when the infections are occurring. A spray at the pink bud stage may be helpful as a time when many fungi become active and again in late summer to protect new shoot growth. Don't be dismayed if you still see canes dying next year, you need to keep up the effort several years to see an effect. Best of luck.