Today, I ran the MaluSim model for both Central Virginia <pdf> and Winchester <pdf>.
For Central Virginia, fruitlets are just starting to approach the 10 mm stage. It looks like the best chance to get a strong thinning response will be Wednesday and Thursday. After that, the model is showing that chemical thinners will have more of an “average” response. Target blocks that have a heavy crop load on Wednesday and Thursday, and leave blocks with more frost damage and lighter crop loads to thin on Friday and over the weekend.
Table 1. Fruitlet sizes at Silver Creek Orchards.
| 1-Apr | 28-Apr | 30-Apr | 2-May | 6-May | |
| Empire | Silvertip | Petal Fall | 5.6 | 7.3 | 10.9 |
| Red Delicious | 5.7 | 6.5 | 9.3 | ||
| Pink Lady | 5.4 | 7.5 | 8.3 | ||
| Gala | 5.4 | 6.4 | 8.8 | ||
| Fuji | 4.4 | 5.8 | 7.8 | ||
For the Winchester area, most blocks are at petal fall or just beyond. We’re forecasted to have some summer-like weather over the next several days, which will cause a fairly strong carbohydrate deficit in the trees. Petal fall thinning sprays rarely over thin, even in hot weather, however blocks with fruitlets approaching 10 mm may see a strong thinning response from applications made over the next three to four days.
I will run another set of models on Friday. I will also start posting fruitlet sizes from fruit at the AREC. Download the above linked pdf files to view the full reports.