Apple Thinning Update Based on the Carbon Balance Model
Posted: May 24, 2011
We ran the model based on weather data for upper Adams County and it shows several windows of carbohydrate stress in May 2011 when thinning may have been very strong (see figure). On Tuesday morning, May 24, 2011, we entered weather predictions for the coming week. The model predicts that there will be a large block of time over the next several days when fruits will be very sensitive to chemical thinning.
The model is still experimental, but I believe it reflects stresses that affect fruit set. While some blocks will still need to be thinned, growers are advised to monitor the weather forecast, to carefully re-assess the need to thin, and to consider reducing the strength of the thinner tank mix. This is done primarily by using lower rates of the thinners themselves, but also by reducing or dropping additives that promote thinning.