Fruit thinning, branching, and stop-drop of pears : New England Tree Fruit Management Guide : UMass Amherst

Written by: Win Cowgill, Win Enterprises LLC

Chemical fruit thinning

Some general comments on chemical fruit thinning of pears, including Asian pears:

use/calculate diltue tree volume, which is typically 100 to 200 gallons per acre for pears; then
when applying chemical thinners, use the table rate below per 100 gallons (dilute TRV)
dilute (1X), up to 2X concentration works best with chemical thinners, do not exceed 4X concentration
if spraying concentrate, also concentrate the thinning chemical as you would any other pesticide application
apply chemical thinners when the temperature is rising into the 70's or low 80's and will remain there for 3 to 4 days
for Aian pears, apply chemical thinners when largest fruits are 10 to 14 mm in size; 6-BA (Maxcel, Riteway, Refine) at 200 ppm (high rate) has worked good on Hosui and Kosui Asian pears in trials, however, Asian pear varieties differ in their sensitivity to chemical thinners
for more detailed information, see the following publications

Chemical thinners
timing	product	concentration	rate	comments
5-7 days after petal fall	Amid-Thin W (NAD)	10 to 50 ppm	1.6 to 8 oz per 100 gal	Label specific for use on Bartlett and Bosc.
14-21 days after full bloom	Fruitone-L, PoMaxa, Refine 3.5 WSG	10 ppm	4 to 8 oz per acre	Apply as soon as fruit set is apparent and weather favors chemical thinning efficacy. Late applications may result in pygmy fruit. Apply when temperature is 70 to 75 F. Thinning efficacy depends on variety.
fruit size 8-14 mm (7-28 days after bloom)	Maxcel, RiteWay	75 to 200 ppm	80 to 128 fl oz per 100 gal	Start with 150 ppm for Bartlett, 75 ppm for Bosc. Apply when temperature is 60 to 85 F. See comments.
fruit size 8-14 mm (7-28 days after bloom)	exilis Plus	75 to 200 ppm	46 to 122 fl oz per 100 gal	See comments
fruit size 8-14 mm (7-28 days after bloom)	exilis 9.5 SC	75 to 200 ppm	9.6 to 25.6 fl oz per 100 gal	See comments
fruit size 5-20 mm	Protone®	100 to 500 ppm	6.6 to 33.1 oz per acres	Make 1-2 application, but one application during a period of carbohydrate deficit is usually sufficient. Protone® may be a particularly good pear thinner.

Branching young trees
Timing	product	concentration	rate	comments
BEFORE buds break in spring on 1-year old wood	Maxcel, Promalin; exilis plus, exilis 9.5 SC	5,000 ppm	see label	If dormant buds are present on one-year-old wood only. DO NOT apply after bud break. See product labels for more details and instructions.
AFTER bud break in spring on 1-year old wood	Maxcel, Promalin; exilis plus, exilis 9.5 SC	500 ppm	see label	If buds have broken, and the leaf tissue is showing on one-year-old wood. Apply by spraying with a back-pack sprayer. Works best when temperatures are warm and there is enough tissue to absorb the PGR. Note: Never add surfactant to a solution of MaxCel as it is already included in the formulated product. Promalin should be combined with a NIS following the label instructions.

For more information on branching young trees, see the UMass Fact Sheet F-140 Branching Young Apple Trees with Plant Growth Regulators

Pre-harvest fruit drop control
tming	product	concentration	rate	comments
7-14 days before anticipated harvest	ReTain	NA	333 g per acre (one pouch)	Apply in sufficient water for good coverage. Add organosilicone surfactant at 12 oz per 100 gallons.
5-7 days before harvest	Frutone-L, PoMaxa, Refine 3.5 WSG	10 to 15 ppm	4 to 6 oz per 100 gal	Apply 7 days before harvest to D'Anjou, Bosc, Bartlett. Make separate sprays to early, mid, and late varieties.
5-7 days before harvest	Refine 24.2L	NA	2 to 4 fl oz per acre	Bartlett, Bosc only. Effective in 3-4 days after application and controls drop for 2 weeks.