[NAFEX] controlling black knot

Alan Haigh alandhaigh at gmail.com
Sat May 9 17:10:39 EDT 2009


I manage and grow a lot of highly black knot susceptible plums in my own
nursery and on the many orchards I manage, so I have a lot of experience
dealing with this scourge.  During the growing season I usually have a
strong bladed pocket knife with me so I can cut out galls whenever I see
them on plums in my nursery and orchards I manage.  I don't actually cut
back too far beyond the galls themselves unless discolored wood extends much
beyond. I don't do anything to disinfect between cuts anymore and won't
until someone shows me evidence that the extra time will pay adequate
dividends.  Just didn't seem to help much in my anecdotal experience.

I used to spray all the cuts with Bravo but I'm not sure that was very
helpful either.  What really seems to matter is just keeping up with it as
much as possible and to remove all the black-knot you can on several
occasions during the growing season and then thoroughly cleaning up during
dormancy.  While it's also useful to eliminate wild cherries I have clients
with such trees loaded with galls standing right next to plums I've planted
that haven't seemed to exacerbate the problem much.

In addition to the knife with a tanto blade I  use my pruning shears and
Silky Gomtaro 300 pruning saw which all help me to remove these things.
Spring has been wet lately so diligence is required.  I've never lost a plum
to this disease in 20 years but I've sure lost a  few branches.  It's a good
reason to keep plums growing vigorously.  Methely is the most susceptible
plum to black knot I know and the Japs in general are more susceptible than
Euros.  Italian plum hardly gets it at all.
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