Getting the most out of ReTain

Jack Bartels, Sumitomo Agrosolutions Australia

ReTain® contains aminoethoxyvinylglycine (AVG), a naturally occurring fermentation product that has been helping growers manage their apple harvest for over 20 years. ReTain inhibits ACC Synthase, the key enzyme pathway used for ethylene to be produced. Ethylene affects plant processes such as fruit maturation, ripening and fruit drop. When used correctly ReTain is a proven tool that allows growers to delay harvest, increase fruit size, increase firmness, and improve fruit quality for the fresh market or coming out of long-term storage.

Application

ReTain has two key application windows which might vary slightly depending on your end goal.

• Applying ReTain 21-28 days before harvest will give you the best response for delaying fruit maturation, increasing fruit size and decreasing fruit drop.
• Applying ReTain 7 days before harvest will have a larger impact on improving fruit quality and storage potential but it won’t significantly delay harvest.

There is no need to pick one application timing over the other.

To ensure good coverage and the best performance ReTain should be applied with Maxx Organosilicon Surfactant. Applying ReTain when drying conditions are slower such as early morning will ensure adequate absorption.

The earliest time that fruit can be harvested for long term storage is normally within a week of the first signs of starch being converted to sugars, when cut apples are tested with iodine. This is a starch pattern index (SPI) of about 1.5 on the chart shown below. Fruit going straight to market will generally be picked later with an SPI of roughly 4. It is important that you pick at the right time for your intended goal. Because poor quality fruit going into storage won’t improve. Fruit which is picked too late and put into storage will also be more likely to develop disorders such as internal browning. It’s for this reason it’s important to be flexible with your harvest plan.

Figure 1: Starch Pattern Index Chart

Improving Storage Potential

Quality at end consumption is always the main goal but when apples go into long term storage this can be harder to achieve. ReTain maintains the quality of fruit well after it has been picked. As shown below ReTain treated Galas have better firmness, background colour, less greasiness & less physiological disorders coming out of storage. This includes fruit that is placed into 1-MCP storage.

Figure 2 & 3 ENZA/ESP Monitoring Blocks, Hawkes Bay

Harvest Management & Increasing Size

Managing a harvest can become a complex task when considering parts of the process such as organising staff, packing, storage, and transport. By delaying fruit maturation ReTain gives you extra time to assign your resources efficiently allowing you to pick fruit at the ideal maturity. As a result of delaying maturity, ReTain can provide larger fruit at harvest.  Galas and Braeburn which produce higher levels of Ethylene can increase yield by 1% per day harvest is delayed. Lower ethylene producing verities such as Fuji and Granny Smiths respond well to ReTain by having improved internal pressures and skin finish.

Summary

ReTain is a proven tool with important benefits for growers including:

• delayed harvest timing
• increased fruit size and firmness
• improved fruit quality particularly coming out of long-term storage.

Growers should plan their ReTain usage well before harvest and monitor their crops to get the largest and best quality fruit.

For more information and assistance with starch testing and Retain application timing reach out to your agronomist, advisor, or local Sumitomo AgroSolutions representative.