Every year I lose a few canes on my red currants. It's often plump
young canes that die over the winter, and if I cut them off halfway,
the pith is gone, so I would guess it's some sort of stem-boring
insect. I've ignored it in the past, and just cut off the dead canes
in the spring - sort of letting the insects chose my pruning strategy
- but the problem seems to be getting worse.
I had a much more serious problem with raspberry cane borers a few
years ago, and I seem to have solved it by careful hygiene - removing
canes as soon as they show signs of wilt below the level of the bugs,
and disposing of the prunings away from my plants. So I wonder if I
ought to address the currant bugs the same way.
Does anyone know at what time of year they hatch? Is it late in the
season enough that I can reliably tell which stems will sprout and
which are affected? Is there any other sign of affliction that I
should look for as an earlier warning?