Like apple, chemical thinning in pear is intended to reduce the current season’s crop load in pursuit of three fundamental goals: 1) inhibit fruit set to minimize green fruitlet hand thinning; 2) improve size and quality of surviving fruit; and 3) promote return bloom to encourage annual cropping. While many pear varieties largely self-regulate their crops without chemical intervention, well-managed chemical and hand thinning programs can increase the long term profitability of some varieties including Bartlett. Some pear blocks can struggle to set commercially adequate levels of fruit and it may be advisable to clearly assess pear set before applying chemical thinners, especially when conditions have been cool and/or wet during bloom.
| Symptom/Behaviour | Chemical | Rate per Acre | REI | PHI | Notes |
|---|---|---|---|---|---|
| All varieties | 6-BA Exilis 9.5 SC | 9.6 - 25.6 fl oz | 12 h | 86 d | |
| 6-BA MaxCel | 48-128 fl oz | 12 h | 86 d | BA may be applied when pears are 5-15 mm in diameter to reduce fruit set, increase fruit size, and promote return bloom. | |
| ABA ProTone SG | 6.6 - 33.1 oz | 4 h | none listed | Target upper portions of tree canopy and apply during slow-drying conditions for better results. ABA may cause significant leaf yellowing and/or abscission.Organic | |
| Bartlett, Bosc | Naphthaleneacetamide Amid-Thin W | 1.6-8 oz | 48 h | 2 d | |
| NAA Fruitone L | 4 - 8 fl oz | 48 h | 2 d | See label for details | |
| NAA PoMaxa | 4 fl oz | 48 h | 2 d | Can be used to thin pears 15-28 days after full bloom. For best results, apply NAA products with a surfactant (wetting agent) when temperatures are between 70 and 75 F. | |
| Bartlett, Bosc, Comice | NAA Refine 3.5 WSG | 12 - 20 oz | 48 h | 2 d | |
| NAA Refine 6.25L | 8-12 fl oz | 48 h | 2 d | Can be used to thin pears 15-28 days after full bloom. For best results, apply NAA products with a surfactant (wetting agent) when temperatures are between 70 and 75 F. | |