Internal defects from extreme summer heat

November 23, 2021

Image of an apple thats been cut into with threadlike corking showing

Threadlike corking from water *(and calcium) being pulled out of the fruit during heat / water stress

The extreme heat we experienced the end of June resulted in some internal fruit disorders that are starting to show up now. Among these are drought spot, internal browning, and the development of cork. Some of the cork that has shown this year has an unusual appearance of being thread-like or “veiny”.

I believe that in some extreme cases, the heat and water stress pulled water (and calcium) out of the fruit and into the leaves to help the trees cool themselves as the root system couldn’t keep up with the water demand. As the water was pulled out, cell walls collapsed along the vascular route and created the thread-like corking appearance as illustrated here. Fortunately, our modern internal defect sorters will catch these and keep them from getting into a packed box, but they do illustrate some of the stress the trees went through.

Byron Phillips, Wilbur-Ellis Key Account Manager


Drought spot on a gala apple, sunburn browning on apple, internal injury under the sunburn browning.An apple cut in half showing brown spots all over