Tree Fruit Newsletter — June 2, 2026
Thinning Outlook
Most of our orchard blocks have excessive fruit set. Gala, McIntosh and Cortland have 4 to 5 fruitlets per cluster with almost no flowers dropping. Honeycrisp is showing signs of fruit set in most of the king blooms, but for side blooms, it’s too early to tell. In Macoun, it’s too early to see fruit set, but the trees are loaded with too many clusters of fruitlets.
I recommend checking each block to estimate the crop load potential and the amount of thinning needed. Apply higher rates of NAA (naphthaleneacetic acid) or BA-type (benzyladenine) thinners where needed.
The long-range forecast indicates warm temperatures through the week making this a good time to apply thinners. The Network for Environment and Weather Applications (NEWA) ‘Carbohydrate Thinning’ model suggests applying standard rates of chemical tomorrow which is as far forward as it goes today. As temperatures warm up, expect chemical thinners to become more effective. Hot temperatures are not in the forecast, so excessive thinning is not expected.
Because apple varieties vary in how they respond to chemical thinners, I am including the Tree Fruit Guide section with suggested rates for each variety.
| Variety | Petal Fall (1 week after bloom) |
8-14 mm fruit size (2-3 weeks after bloom) |
|---|---|---|
| Ambrosia | 3 oz NAA + 1 pt carbaryl | |
| Cortland | 1 to 2 pt carbaryl | 1 to 2 pt carbaryl |
| CrimsonCrisp | 3 oz NAA + 1 pt carbaryl | 3 oz NAA + 1 pt carbaryl |
| Delicious | 2 oz NAA plus 1 pt carbaryl | 64 oz 6-BA plus 1 pt carbaryl plus 1 qt ultrafine spray oil |
| Empire | 2 oz NAA + 1 pt carbaryl | 64 oz 6-BA + 1 pt carbaryl OR 3 oz NAA + 1 pt carbaryl |
| Evercrisp | 1 to 2 pt carbaryl | 1 to 2 pt carbaryl |
| Fuji | 64 oz 6-BA + 1 pt carbaryl | 64 oz 6-BA + 1 pt carbaryl |
| Gala | 3 oz NAA + 1 pt carbaryl | 64 oz 6-BA + 1 pt carbaryl |
| Gingergold | 2 oz NAA + 1 pt carbaryl | |
| Golden Delicious | 3 oz NAA + 1 pt carbaryl | 64 oz. 6-BA + 1 pt carbaryl OR 6 oz NAA + 1 pt carbaryl |
| Granny Smith | 3 oz NAA + 1 pt carbaryl | |
| Honeycrisp | 4 oz NAA + 1 pt carbaryl | 3 oz NAA + 1 pt carbaryl |
| Jonagold | 3 oz NAA + 1 pt carbaryl | |
| Lady Apple | 3 oz NAA + 1 pt carbaryl | 4 oz NAA + 1 pt carbaryl |
| Liberty | 3 oz NAA + 1 pt carbaryl | 64 oz 6-BA + 1 pt carbaryl OR 3 oz NAA + 1 pt carbaryl |
| Ludacrisp | 3 oz NAA + 1 pt carbaryl | 3 oz NAA + 1 pt carbaryl |
| Macoun | 3 oz NAA + 1 pt carbaryl | 64 oz. 6-BA + 1 pt carbaryl OR 4 oz NAA + 1 pt carbaryl |
| McIntosh non-spur type | 2 oz NAA + 1 pt carbaryl OR 36 oz 6-BA + 1 pt carbaryl | |
| McIntosh spur-type | 3 oz NAA + 1 pt carbaryl OR 48 oz 6-BA + 1 pt carbaryl | |
| Mutsu (Crispin) | 2 oz NAA + 1 pt carbaryl | |
| Northern Spy | 3 oz NAA + 1 pt carbaryl | 2 oz NAA + 1 pt carbaryl |
| Paulared | 3 oz NAA + 1 pt carbaryl | 3 oz NAA + 1 pt carbaryl |
| Sweet Sixteen | 3 oz NAA + 1 pt carbaryl | 3 oz NAA + 1 pt carbaryl |
| Zestar! | 1 to 2 pt carbaryl | 1 to 2 pt carbaryl |
Renae Moran
University of Maine Cooperative Extension: Tree Fruits
PO Box 179
Monmouth, ME 04259
(207) 933-2100
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