A couple of weeks ago I wrote an article about all the resources we have available for precision thinning. This time I want to provide recommendation specifically on chemical thinning options.

1) At Petal Fall (fruits 5-6 mm; 100-125 DD since bloom):

• Sevin (very mild thinner; good options in year where we have substantial frost damage; except if 75% kings are damaged)
• Amid-Thin (mild thinner and cold be a good substitute for NAA and Sevin)
• Maxcel + Sevin (it works great if the temperatures are warm, but with cold temperatures below 70℉ no effect)
• NAA + Sevin or Maxcel + NAA
• At petal fall almost all chemicals have moderate effects, so there is very little risk of over-thinning because fruits are not so sensitive to thinners.
• Examples for Mature Gala NAA (3oz/100 gal TRV* dilute basis) + Sevin (1pt/100 gal TRV dilute basis)
• Example for mature Honeycrisp NAA (4oz/100 gal TRV dilute basis) + Sevin (1pt/100 gal TRV dilute basis)

2) Petal Fall (fruits 11-13 mm; DD=200-250 since bloom)

• NAA + Sevin; or Maxcel + Sevin; or Maxcel + NAA (Good option if you don’t want to use Sevin; not for Fuji and Red Delicious)
• For HoneyCrisp NAA is great because it helps with the return bloom
• Examples for mature Gala: Maxcel (64oz/100gal =96oz/acre) + Sevin (1pt/100 gal=2pt/acre)
• Example for mature Honeycrisp: NAA (3oz/100 gal TRV dilute basis) + Sevin (1pt/100 gal TRV dilute basis)

3) Petal Fall (fruits 15-20 mm)

• NAA + Sevin; or Maxcel + Sevin + Oil; or Etherl + Oil
• NAA losses its effectiveness when fruit is over 15 mm
• Example For Mature Gala: Maxcel (64oz/100 gal TRV dilute basis) + Sevin (1pt/100= gal TRV dilute basis) + Oil (1pt/100gal water) don’t concentrate oil(directed to the upper part of the tree)
• Example for mature Honeycrisp: Sevin (1pt/100= gal TRV dilute basis) + Oil (1pt/100gal water) don’t concentrate oil(directed to the upper part of the tree)
• 1.5 pints per 100 gallons Etrhrel, with 1-quart Sevin and oil. One-quart horticultural spray oil can be added to this tank to boost the thinning response.

*TRV= Tree Row Volume.

This article was posted in Apples and tagged Amaya Atucha, apple thinning, Apples, chemical thinning, precision chemical thinning, thinning.