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May 22 Freeze Injury

On May 22, temperatures in the Thousand Island region plunged to the upper 20s (27-31 degree F), causing extensive, late freeze injury to shoots that were out 6-12 inches:

1. Frost injury was extensive, with some portions of blocks having upwards of 90+ % of shoots frozen.

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2. Many shoots were totally frozen; some were partially frozen from the tips down.

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3. Some shoots appear to be intact.

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4.  Secondary buds,  basal buds (latent buds in cordons and trunks) and suckers are starting to emerge (May 29).

 

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Consequences.  Loss of primary shoots will severely limit crop potential for 2015.  Secondary buds may produce fruit, but it will be about a month behind the crop on the primary buds that survived the freeze.

Management. 

1. For fully frozen shoots, there is no need to remove them from the trellis.  They will dry up and are not in any sense a ‘reservoir’ for diseases.

2. Partially frozen shoots:  If just the shoot tip was frozen, they might throw lateral shoots off of the remaining green tissue, and possibly inhibit base buds from pushing.  Should they be removed?  Probably not, but I might experiment with doing so, and see if the latent buds push as a result.

3. ‘Second crop’: The late crop may, to a certain extent, ‘catch up’ as the season progresses.  (See Paolo Sabbatini’s article in Northern Grape News, May 2015 issue).  But it will probably ripen later and need to be harvested later.

4.  Defruiting?  Should the second-crop shoots be defruited to allow vines to recover better?  Probably not, as the vines still have a mature root system and will be looking to push out remaining reserves.  But the canopy development will be delayed.

5. Spray program?  This will disrupt timing in relation to disease management.  If you have no crop, a minimal spray program aimed at keeping the foliage healthy (powdery and downy mildew) may need to be adopted.

6. Future updates?  We’ll be following this event and trying to collect data on its impact in coming weeks.  Look for further updates on a regular basis.

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