Cane blight at end of season?

Cane blight infection at tip of cane where it had been pruned as a primocane.

Cane bight symptoms in entire canes.  Dead canes are silvery/gray in appearance. Photo phil Brannen. UGA

As the blackberry season winds down, there are several reports of loss of crop and cane death before the crop ripens. This is often occurring in plantings that are low or no spray such as homeowners and small commercial plantings. The canes become infected when they are primocanes as tipping or pruning occurs in the summer. 

In at least one instance, samples sent into the NCSU Plant Insect and Disease Clinic have confirmed that Cane Blight caused by the fungus, Leptosphaeria coniothyrium. This disease is common in roses and some ornamentals. 

Here is a link to the disease. http://extension.uga.edu/publications/detail.cfm?number=C894

Here is a link to the IPM manual that has control methods: http://www.smallfruits.org/SmallFruitsRegGuide/Guides/2016/2016BrambleSprayGuide.pdf

and and article on the disease http://www.smallfruits.org/bramble/pestinformation/caneblightfactsheetii.pdf

Please send in samples to your states disease clinic to confirm any diagnosis.

Phil Brannen, UGA also sent these comments on fields with infected canes:

"On the current canes, there is nothing to be done to prevent it from spreading.  After harvest, I would immediately cut out the old floricanes.  The most full-proof approach to wiping out old inoculum would require complete removal and burning of the old canes.  Some producers hesitate to do this, so complete flail-mowing of the canes may work.  However, I would be careful to say that we don’t have research information to say that this completely destroys the inoculum.  I would tip or pinch prune where possible on the new primocanes, as opposed to large pruning cuts, and I would apply Pristine or Rally (make sure they are labeled for your state) after each day of pruning to prevent infection on the pruning cuts. Hopefully, this will break the cycle."

Blackberry tipping

Now is the time to tip your primocanes. The arrow shows the point were the cane was tipped. Tipping means that you only need to use your fingers to remove the top of the cane. This results in a smaller wound and will be less likely result in diseases entering this area (see earlier posts on Cane Blight). If you need to use pruners, you will need to apply a fungicide afterwards.

Two ovals show where the axillary buds below the tip are starting to elongate. Instead of having just one cane to produce fruit, you now will have 2 branches.

For floricane-fruiting blackberries, you should be tipping them about 6" below the top wire. This will enable you to redirect the growth in a "horizontal direction" and increase your fruiting area for next year. I use "" around horizontal because the canes are growing vertically in this picture and will do so in your field. Later in the year, they will start to bend over and will form the framework for next years fruiting laterals, and be more or less horizontal with some strategic training.

For primocane-fruiting types, we have found that tipping them at about 3-4 ft., will result in higher yields. We have yield data and a published paper that shows all this data, however, validation in the field is always great. Last week I was visiting a grower that had some Prime-Ark 45. He tipped some plants (on my recommendation) and did not tip some, just to see what happened. He told me last week, yields were much better when the plants were tipped. The picture above is from his field, where all plants were recently tipped.

Also see last years post on this subject:
http://teamrubus.blogspot.com/2011/05/blackberry-pinchingtipping-vs-pruning.html