NEWA Carbohydrate Run for May 4, 2021

All sites report only a mild efficiency for the application of chemical thinners as indicated by the blue text in the columns. Because we have not reached the targeted GDD Base 39°C of 200–250 hours; the general recommendations are for a higher rate of chemical thinner than your standard. The predicted maximum temperatures for the next few days are also not very high. Monday and Tuesday looked to be the warmest. Remember that most chemical thinners work best when temperatures reach above 75°F. Rainfall has kept solar radiation lower, resulting in less photosynthesis. The 7–Day Carbohydrate Balance graph below each table does not predict a large carbohydrate deficit.

(The MaluSim Carbohydrate Model)

Two points should be considered when looking at this information. First, you need to use your dates of green tip and full bloom. This may differ based on cultivar. The second is using the weather data from a site somewhat near your orchard. You should also consider if you had any frost damage from the week of April 19.

Apple Carbohydrate Thinning Models for Pennsylvania Counties

• Adams County
• Bedford County
• Butler County
• Centre County
• Erie County