Assessing Grapevine Bud Damage
Damage from low winter temperatures is arguably the greatest risk to sustainable profitable winegrape production in the eastern US. The majority of Maryland vineyards have not experienced a significant amount of low-temperature damage over the past decade or so, however some vineyards have experienced damage this winter (2013/2014). The following “Timely Vit” will give an overview of how to assess the damage and how to modify your pruning based on the assessment. Please see the previous “Timely Vit” in the series on “Understanding Grapevine Bud Damage” for an overview of how vines attempt to prevent damage, the conditions which influence the level of damage, and types of damage.
When temperatures below 0˚ F take place, it is prudent for growers to collect canes and assess bud damage prior to pruning. Here are some guidelines for bud damage assessment and pruning adjustment.
How to assess the amount of low-temperature damage to buds (Handle sharp objects with CARE!!)
1) |
Collect enough canes so that you have about 100 buds from the block or variety that you are checking.
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2) |
Bring the canes indoors and allow them to warm at room temperature for a minimum of 24 hours. This allows the damage to develop and makes it easier to differentiate between healthy and injured buds. |
3) |
Use a sharp razor blade to cut cross-sections of the bud until you can tell if the large primary bud is healthy (green) or injured (brown) (all green in figure 5.)
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4) |
Count the number of dead or injured buds, and divide by the total number of buds sampled to get the percentage of injury.
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