2018 Crop Protection Guide for Tree Fruits in Washington

Bioregulator Sprays

Monday, March 25, 2019

Pear Chemical Thinning

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.

BA (MaxCel, Exilis Plus, Exilis 9.5SC) may be applied when pears are 5-15 mm in diameter to reduce fruit set, increase fruit size, and promote return bloom. NAD (Amid-Thin W) may be applied to reduce pear fruit set 5-7 days after petal fall. NAA (K-Salt Fruit Fix 200, K-Salt Fruit Fix 800, Fruitone, PoMaxa, Refine) 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. Please refer to individual product labels for more detailed information. No chemical bloom thinners are registered for use in pear at this time.

Tree Fruit Research & Extension Center, 1100 N Western Ave, Washington State University, Wenatchee WA 98801, 509-663-8181, Contact Us