Here are the berry weight curves for 1999, 2000, 2001 and the start of the 2002 curve for balanced pruned vines at the Fredonia Lab.
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Many growers are out checking vineyards and possibly picking test plots for crop estimation. Here is the current berry weight information to help you out.
On average, Concord berries are 20% of their final berry weight at 20 days after bloom and 50% their final berry weight at 30 days after bloom. Typically, 30 days after bloom and 1200 GDD are very close to each other. With the above average temperatures we have had since bloom, 2002 berry weights are a bit off from the average.
In 2002, Concord berries were 40% of their projected final berry weight at 20 days after bloom and almost 50% of their projected final berry weight at 25 days after bloom (we also hit 1200 GDD at 25 days after bloom). By 30 days after bloom (Friday or Saturday of this week) the berries will probably be more in the area of 60% of their final berry weight.
The larger than normal berries for this time of year could throw off your crop estimate. If you are picking vines for a crop estimate this week, I always recommend taking a random berry sample (100 berries or more) and getting a berry weight that you can compare to a projected final berry weight.
What is my projected berry weight guess? Given the high crop potential in unfrosted vineyards, the current weather conditions, and the current berry weight, I would predict that balanced pruned vines will have about 3.2 gram berries at the end of the season. Minimal pruned vines will have about 2.7 gram berries and 80 to 120 node vines will fall in the middle range of 2.8 - 3.0 gram berries.
Here are the berry weight curves for 1999, 2000, 2001 and the start of the 2002 curve for balanced pruned vines at the Fredonia Lab. |
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Thanks to the Fredonia Lab crew, we have new pressure bomb readings to determine the water status of Concord vines. In short, pressure bomb readings of 6 and 7 indicate good vine water status and correlate with high potential photosynthesis. Readings around 8 put the vine on the edge of water stress where we record slight decreases in photosynthesis. Readings of 9 or 10 indicate vine water stress and correlate with reductions in photosynthesis from 40 to 60%.
Pressure bomb readings taken today (7/16/02 - 1pm) are: