ReTain Your Apple Crop For Timely Harvests

Erika DeBrouwer, Tree Fruit Specialist, OMAFRA

Many growers have started harvest on some apple varieties already, and the major varieties in the province are following quickly. In preparation for harvest, proper maturity is something that needs to be considered and should be known to maximize quality for sales and long-term storage. A successful harvest time will be reflected in your payments when harvest is performed at optimal times.

Picking at optimal times has become increasingly difficult as acreage of Gala, Honeycrisp and Ambrosia continue to rise. There are a few options available to extend the harvest window of your apples, including ReTain® (AVG) and Harvista (1-MCP). Harvista can be used 3 weeks in advance of harvest and up to 3 days of harvest. For further information regarding Harvista please refer to the following: Harvista Label, Timing of Harvista, Plant Growth Regulator Use in Apples, along with the article titled “Effects of 1-MCP Orchard Spray on Apple Quality” written by Dr. Jennifer DeEll found in the August 2020 issue of the Orchard Network Newsletter.

One potential solution to space out your harvest window is the use of ReTain®. ReTain® effects the fruits ethylene production, slowing apple maturity, allowing for a delayed harvest.

When you should consider ReTain®:

Harvest will require more than 5 to 10 days to harvest with your existing crew
The cultivar has a tendency for pre-harvest fruit drop
Fruit needs better size or colour
Fruit cracks around the stem
Fruit develops greasiness or water core

Some key points about ReTain®:

Treat only healthy trees
Utilize starch iodine testing to monitor maturity
Store ReTain® treated fruit separate from untreated to prevent ethylene exposure
Keep good records to learn more of how to use this tool
ReTain® can lower colour development, allow 10-14 days for apple to reach natural colour
Use lower rates during periods of hot weather
Generally, apply ReTain® 3 to 4 weeks before harvest
Varieties that require multiple picks should be applied with ReTain® 4 weeks before 2^nd harvest, delaying 2^nd, 3^rd and 4^th picks.
It is better to apply early than later, as once the ethylene pathway starts ReTain® isn’t as effective
Jonagold and Gala are more sensitive to ReTain® in comparison to McIntosh
A surfactant should be added to the tank
- Do not use a surfactant concentration greater than 0.1% (v/v)
- To reduce foaming, add the adjuvant last and minimize agitation.
ReTain® is only labelled for 1 pouch per acre and single applications
Combination with NAA is not recommended in very warm conditions at harvest as NAA may counteract the ReTain® effect. – Honeycrisp
Always read the label and follow instructions

Below is cultivar specific data that has been found from research conducted by Valent BioSciences. This data is not advised on the label so it is possible you may not see same results in own orchard. For additional information please refer to the ReTain® Technical Manual, and be sure to be in the correct section (U.S. & Eastern Canada) regarding suggested rates and observations.

Gala

Brookfield, Buckeye, Gale, etc. (High colouring red strains)

Single application
- 1 pouch per acre at 3 weeks before harvest
- Blocks prone to cracking should have no less than one full pouch of ReTain®
Split application (to minimize colour delay)
- ½ pouch per acre at 3 weeks before harvest
- Followed by ½ pouch per acre 1 week before harvest
- This provides no more than 7 days of harvest management and quality

Standards, Royals, Imperials etc. (Colour sensitive strains)

Single application
- 1 pouch per acre at 1 – 2 weeks before harvest

Honeycrisp

Harvest management and drop control (standard program)
- ½ to 1 pouch per acre at 3 weeks before harvest
- Higher rates result in longer delays in maturity and colour development of 2 – 3 weeks
Extended harvest window and drop control
- ½ pouch per acre applied at 3 weeks before harvest
- Followed by ½ pouch per acre 1 week before harvest
Minimize colour delay on colour sensitive strains
- ½ to 1 pouch per acre at 7 to 14 days before harvest
- Lower rates (less than ½ pouch) will provide shorter drop control and quality retention

McIntosh

Maturity delay and stop drop (standard program)
- 1 pouch per acre applied 3 to 3½ weeks before harvest
Minimize colour delay on colour sensitive strains
- ½ pouch per acre at 2 weeks before harvest
- This is for short-term delay and pre-harvest drop control

½ pouch 3 to 4 weeks before harvest
- Followed by ½ pouch 1 to 2 weeks before harvest
- This is for longer drop control and harvest management

Red Delicious

Harvest management, drop control, watercore reduction (standard program)
- 1 pouch per acre at 3 to 4 weeks before harvest
Enhanced drop control, watercore reduction
- 1 pouch per acre at 3 to 4 weeks before harvest with NAA at 5 – 10 ppm at 1 week before harvest

1 pouch per acre at 2 weeks before harvest combined with NAA at 10 ppm

½ pouch per acre at 3 weeks before harvest + ½ pouch per acre combined with NAA 5 – 10 ppm at 1 to 2 weeks before harvest

Ambrosia

Highly sensitive to ReTain®, which is why lower rates are recommended

Standard Program
- 1 pouch per acre 3 to 4 weeks before harvest
Poor colouring conditions
- ½ to 1 pouch per acre at 1 to 2 weeks before harvest

Further Information

Cline, J. 2011. Primer for Use of ReTain® in 2011. Orchard Network Newsletter. 13: 3. https://journals.scholarsportal.info/pdf/22915907/v15i0003/3_pfuori2.xml

Huffman, L. 2014. Using ReTain® to Manage Apple Harvest. http://omafra.gov.on.ca/english/crops/hort/news/orchnews/2014/on-0814a2.htm

Valent BioSciences. 2021. ReTain® Technical Manual. https://issuu.com/valentbiosciences/docs/retain_tech_manual_final_12-27-21

Valent BioSciences. 2020. ReTain: Plant Growth Regulator. Reg Number: 25609. https://pr-rp.hc-sc.gc.ca/1_1/view_label?p_ukid=245385021

ReTain Your Apple Crop For Timely Harvests