2024 Capital Region 10-13mm Thinning Recommendations
Dr. Terence Robinson and Mike Basedow
Below is a review of recommendations from our Fruit Set Meeting that we held in Ballston Spa on May 22nd. The recording of which can also be viewed below:
Assess each block for flower damage.
We once again found variable levels of set throughout Saratoga county when evaluating orchards on Wednesday May 22nd. While there is much variability, and your mileage will vary, Honeycrisp and NY-1 had less damage than Gala, and Mac types like Mac, Cortland, and Macoun had the most. Honeycrisp and NY-1 were missing a few kings, Gala a few more, and the Mac types the most. When making your 12mm thinning decision, we recommend assessing each of your own blocks carefully, and adjust your thinning plans accordingly. We expect the cold damage, along with the carbohydrate deficits we had earlier this week, will likely lead to some good natural thinning as well.
Wait until king fruits are 10-13mm before applying your thinning spray. You can also use the NEWA carbohydrate model degree day calculator to target the best time for thinning. The 10-13mm thinner spray timing generally falls to when DD accumulations after full bloom are between 200-250 DD.
At Clifton Park the 10-13mm thinning window was likely Monday May 20-Thursday May 23. In the Ballston Spa area, we expect this window will likely be Saturday May 25- Monday May 27. Below is the current output from Ballston Spa with a full bloom date of May 9th. Given the variability of bloom dates around the Capital Region, we strongly encourage you to look at the carbohydrate model for your area with your bloom dates.
At 10-13mm, all thinners have a strong effect and are thus effective but also risky. Use the carbohydrate model to adjust your timing and rates. Don’t spray if your 5-day average deficits are -60 or below. With the weather forecast we currently have, the carbohydrate model indicates we are coming out of a severe deficit, followed by a mild deficit, suggesting we should achieve good thinning with our 12mm sprays. There is a risk of over-thinning this year due to the severe carb deficits of the last few days, which were likely a natural thinning event, and there is also a risk of overthinning due to the frost damage we saw. Consider reducing your rates this season to avoid potentially overthinning.
Here are our full rate recommendations for select varieties. Again, consider backing these down where necessary to avoid potential overthinning:
- Gala – Good year to use Maxcel at 64 oz TRVD basis + 1 pt Sevin XLR
- Honeycrisp – use NAA at 3oz TRVD basis + 1 pt Sevin XLR
- McIntosh – use NAA at 2oz TRVD basis + 1 pt Sevin XLR
- Empire – use Maxcel at 64 oz TRVD basis + 1 pt Sevin XLR
- Spur Delicious – use Maxcel at 64 oz TRVD basis + 1 pt Sevin XLR
- Fuji use Maxcel at 64 oz TRVD basis + 1 pt Sevin XLR
Suggested rates are dilute TRV rates. Calculate TRV for each orchard and then a concentration factor:
- TRV/Volume of spray per acre=Concentration factor
- Example: TRV=200 and spray volume is 100 then concentration factor=2
Multiply suggested rates by concentration factor to get rate/acre.
- Example 3oz NAA X Conc factor of 2=6oz NAA/100 gal X 5 for a 500 gallon sprayer=30 oz/sprayer tank
- Example 64oz Maxcel X Conc factor of 2=128oz Maxcel/100 gal X 5=5 gallons Maxcel/sprayer tank
Do not use concentration factor adjustment for Sevin or surfactants.
Nozzle the sprayer differently for the next sprays
1.For the 12mm spray, nozzle so that 75% of the spray is directed to the top half of the tree.
2.For 18mm (if needed) only spray the top of the tree.
Questions? Please feel free to reach out to Mike at mrb254@cornell.edu or 518 410 6823.