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Updated: August 8, 2017
For the next few days total daily carbohydrate production is increasing, resulting in a surplus and the recommendation to increase chemical thinner rates. Looking at the orchard at Rock Springs the first wave of dropping fruit is well underway. These fruit are characterized by their smaller diameter and yellow pedicels. When bending the fruit just a little they quickly drop. Another assessment method is to sharply strike the branch and the abscising fruit quickly drop off.
Earlier this month I indicated that we had two mornings of damaging temperatures--May 8 and 9. Apparently it was not damaging enough because fruit size is expanding and fruit are staying on the trees. However, fruit show cracking in line with where the sepals once were. Many years ago I reported the occurrence of frost and the resulting "pumpkin-shaped" fruit that persisted to harvest. It looks like there may be some of that in some orchards around the state this year, although mostly in central PA and not in major fruit producing counties. Other freeze damage that may appear is skin russet. The Asian pears at Rock Springs show varying amounts of freeze injury. In many cases the calyx lobes were destroyed.
The model was run at approximately noon today.
For more information on the carbohydrate thinning model, visit Carbohydrate Thinning Model. For more details on factors that affect plant growth regulator performance and chemical thinner rates, visit Growth Regulators in Apple and Pear Production.
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