Monday, April 22, 2013

Orange spots on canes? It could be Orange Cane Blotch AKA Orange Felt

Orange Cane Blotch. Picture Gina Fernandez.
Orange Felt or Orange Cane Blotch (Cephaleuros virescens) is a problem that occurs on blackberry canes in the warmer regions of NC. The "disease" is actually a parasitic algae.  It is usually first seen on the floricanes in the spring as yellow/orange disks. Plants with higher infection rates can have the disk shapes join into larger regions on the canes. In mid summer they can become velvety in appearance. Severe infections should be controlled as they will significantly weaken the plants.

I first saw this about 10 years ago in southeastern NC, before the blackberry industry expanded through the state. The site was in the extreme southeastern part of the state. Without the benefit of a digital image, I had assumed it was the more common disease orange rust. However, when I saw the the plants, the symptoms were not what I was expecting. We finally determined it was Orange Cane Blotch.

This disease is now in many counties in NC. I see it most often in plantings with high plant density, lots of vegetation in alleys (weeds or cover crops) and when beds are not raised or do not have plastic. A simple way to tell the difference between orange cane blotch and orange rust is to lightly rub the infection site. When the orange felt colonies are rubbed, they cause a stain, but a light rubbing of an orange felt colony does not cause a stain on your fingers.

Dr. Phil Brannen prepared a circular on this disease, including suggestions for biological and chemical controls. Here is a link:

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