Fruit in the Winchester area is at the ideal size for chemical thinning.
Thinning applications made on Monday through Wednesday of this week will likely see an excessive amount of thinning, especially if fruit was 8-12 mm in diameter. Thinners that were applied on Thursday will likely have a moderate to strong response. Thinners applied Friday (if it stops raining!) through the weekend will have a normal to weak response. If the weather forecast holds, growers should consider slightly increasing rates and using a surfactant for thinning applications made over the weekend. I’ll run another MaluSim model on Monday.
Table 1. Fruitlet sizes (mm) at the Alson H. Smith, Jr. AREC in Winchester.
| Variety | 12-May | 15-May |
| Empire | 10.4 | 12.2 |
| Fuji | 7.0 | 9.0 |
| Gala | 8.7 | 11.3 |
| Goldens | 8.0 | 9.5 |
| Idared | 8.1 | 9.5 |
| Pink Lady | 9.2 | 11.0 |
| Red Delicious | 8.0 | 10.1 |
| York | 7.9 | 10.7 |
Download the full Winchester report:
Fruit in the Central Virginia region is now beyond the size where chemical thinning with 6-BA or NAA is effective. If additional thinning is needed, growers should use ethephon. While these late or “rescue” thinning applications are not very responsive to the carbohydrate status modeled with MaluSim, ethephon does tend to be more active when applications are made on hot days. I will run a season recap for the Central Virginia region in a few days (I was having technical issues accessing the weather station data).