[NAFEX] Dealing with raspberry cane borer
jfruth at tds.net
Sat Jun 14 09:58:17 EDT 2008
Robert C. Mullins wrote, "I have a strange situation. I planted a red
raspberry last year and it seems fine. This year it put on flowers and
started to 'berry-up' but then one day I went out to check on it, and
noticed that the entire flower stem were dead, dead, dead."
It is not so strange at all. If you'll look near the bottom of your
dried up canes, you'll likely find a swelling of the stem or, at the very
least, some stretch marks, symptoms of a cane borer. There is no spray
recommended for its control. The only (approved) method of control is
sanitation. Being in the fruit and berry business, I do it all the time.
So far as I've been able to ascertain, as with aphids, the female gives
birth to live young which are deposited, most often, on a growing primocane
or (rarely) on a fruiting cane. Once deposited at, or near, the apical
meristem, the grub immediately moves to girdle the growing stem. When the
stem is entirely girdled, the stem wilts in a somewhat more exaggerated form
than if caught in direct sunlight. This is the easiest time to recognize an
infestation and deal with it. Look for a faint brown-green line
circumventing the stem - sometimes appearing as a brown internal cavity -
and snip the stem just below the problem area. Separated from the plant,
the stem will wither and dry up killing the grub. Otherwise, after a day,
or more, of wilting, the stem will repair itself and continue growing.
If you fail to catch the infection at its most obvious, there are either
of three other ways of recognizing it on a growing primocane:
1) An infected stem may resume growth exhibiting a slight ess to its cane.
2) An infected stem might be growing at an odd angle.
3) One or more leaves may be crippled, wilted or dried.
If you bend an infected cane into a sharp arch, it will usually snap at
the site of the girdling. Again, snip the cane below the infection and
discard it. When I see a symptom and bending the stem doesn't expose the
problem area, I remove it entirely, just to be sure.
If you fail to deal with cane borer among growing primocanes, snip out
primocanes that have swellings in the Fall or Spring when you prune out the
Pequot Lakes, MN 56472
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