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I have seen a number of these. Most often the cane does not leaf out in the spring, sometimes you will see the leaves of the cane wilt and die. I beleive that the culprit is a clear wing moth that emerges and lays eggs on the cane in early summer - June. The hatchlings bore into the cane and live there most of their life. They almost always bore downward toward the root, I have seldom found the grub in the cane because by the time that you notice it it is too late. The grub is a fairly large white/pink grub.

 

If you see leaves wilting, cut the cane back until you see healthy pith or centers. In the spring, cut thecane back to the first set of good green leaves.

 

There is another similar problen, cane dieback that is caused by greymold. This is much more common in gooseberries than currants. The cane looks similar to those affected ny bareers. This is often noticed while the cane is growing and in full leaf. The leaves yellow, wilt and die. These canes should be removed and disposed of promply.

 

There may be other borers but this is the main culprit.The difference can be seen by splitting the affected cane and if the pith is black or absent the problem is a borer, if the pith seems intact, it is most likley cane dieback. In either case, prompt removal is indicated.

 

 

 

Ed Mashburn
Central PA
Zone 5A