Earlier today, I ran the MaluSim Carbohydrate Model for Winchester. I used actual data from the meteorological station located at the AREC and forecast data from www.intellicast.com and the National Weather Service (NWS). The two forecasts produced reasonably similar carbohydrate balance simulations, so I just show the simulation using the intellicast forecast in the pdf. Also, intellicast provides ten-day forecasts for both temperature and cloud cover, while the NWS only provides a seven-day temperature forecast, with only five-day forecasts for cloud cover data.
This brings us to an important point that I’ve discussed before (and others have discussed about other weather-forecast dependent models), which is that the predictions of future carbohydrate balance are only as good as the weather forecast data that are used as inputs. Many weather forecasts are fairly reliable for three to five days and then lose reliability the further into the future they try to predict weather conditions. The take home message is that the conditions may change by the time we get to the 10 mm fruitlet size on many cultivars. I will continue to watch the weather and will try to run another MaluSim simulation towards the end of this week.
Nonetheless, the model is showing that there is not going to be a very severe carbohydrate surplus nor deficit over the next ten days. This means that you can expect an average or “normal” response from your chemical thinners. At the AREC, some cultivars will probably reach 10 mm this weekend or early next week. Areas to the south may already be at or beyond that size.
By now, you should be able to assess damage from the March 27 freeze. In fact, the damaged fruit has probably already fallen off the tree. If not, damaged fruit can be identified as having a red stem and being easily detached from the cluster. There seems to be a fairly large difference in damage between just a five or 10-foot change in elevation. In some blocks, this might mean using different rates on different rows, or turning on or off the sprayer as you drive up and down hills.