I had a question about use of Topsin M for application to pruning wounds (see label below) and how to best apply this fungicide and others for this purpose. In an ideal world, we could have a sprayer designed specifically to go over the top of the cordons after each day of pruning – a banded application. I have seen photos of such from California, and that allows the best application of concentrated fungicide directly to pruning wounds. Painting on the fungicide is time consuming, so I would likely just concentrate a couple of spray nozzles directly at the cordon and go with that – using an airblast or similar sprayer.  You will likely do a better job if you spray down on the cordon/pruning cuts – assuming you can lift the sprayer and use the upper nozzles.  Temperature comes in to play on this, as we are often pruning in really cold conditions.  However, many days will warm up to above 50 degrees, so fungi can become active.  In addition, on sunny days, the plant surfaces actually heat up much more than the surrounding air, so I think fungi are more active than we might think based on air temperature.  The bottom line is that I think Topsin in particular can help to prevent wound-site infections, and I recommend it in our environment to prolong the productivity of vines. I would not use over 30 gallons per acre, as most material will be going on the ground anyway at this time of year; the key is to cover the cuts with the correct amount of fungicide, and less total spray volume will be more efficient than a greater spray volume for this application timeframe.  Follow the Topsin application with a Rally application two weeks later.

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