Photo: T. Baugher, Penn State

However, if you need a rescue treatment for underperforming previous applications, please refer to the section in the current Tree Fruit Production Guide titled "Late Thinning" (bottom of page 66 and continued onto page 67 in your paper copy). There is a discussion for late thinning depending upon how much fruit you need to remove.

Most of the sites are now beyond 25 days after full bloom or will be so by the end of the week. If you look at the model you will note that there is no longer a recommendation for chemical thinner adjustment although the model will continue to run the numbers. If you need to know what the model recommends look in the "More Info" tab and select "Model overview." The table at the bottom of that page will provide the appropriate recommendation for the 4 day average balance.

This year's weather has certainly been challenging. In addition to the charts for the past week I created two season long charts for Biglerville and Rock Springs. You will notice that in general the two sites had similar trends rising and falling in unison. However, the peaks and valleys for Rock Springs never hit the highs and lows that occurred in Biglerville. We also had cold damage on the mornings of May 8 and May 9 that resulted in damage to the young fruitlets. After looking at the fruit the afternoon of May 8, I thought we would not have any fruit. As it looks now we have fruit albeit some frost rings as well as cracked fruit that look like they will stay on.

Apple Carbohydrate Thinning Models for Pennsylvania Counties

• Adams County
• Allegheny County
• Bedford County
• Berks County
• Butler County
• Centre County
• Erie County
• Lackawanna
• Schuykill County

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 .