July, 1997
Harvest Management Tool for Apples and Pears
Win Cowgill, Area Fruit Agent, Rutgers Cooperative Extension
ReTain is a new harvest management tool labeled for both apples and/or pears.
It has received a full federal label for use in 1997. In 1996 growers applied
and evaluated ReTain on nearly 4,000 acres of apples in 18 states. Half
of the acreage was in the Pacific Northwest, while the rest was used in
the Great Lakes region and eastern U.S. It was used on many varieties including
Red Delicious, McIntosh, Gala, Golden Delicious, Empire, Jonagold, Jonathan
and Rome.
I have had two years experience working with ReTain in New Jersey under
and an EPA-approved experimental use program on seven different apple cultivars
with excellent results. ReTain was evaluated on six grower orchards and
at the Rutgers Snyder Research and Extension Farm on McIntosh, Cortland,
Liberty, MaCoun, Stayman, Mutsu, Empire.
ReTain works by retarding the development of ethylene, the chemical that
causes ripening. The active ingredient is a natural occurring product aminoethoxyvinylglycine(AVG)
which is produced by fermentation.
ReTain is a true harvest management tool with multiple benefits. It works
as a stop drop material, as good or better than NAA, holding drop prone
varieties on the tree. It does delay maturity on average from 7-10 days.
Fruit treated with ReTain can be picked during the normal harvest period
for enhanced retention of firmness in CA or regular cold storage, or harvest
may be delayed, allowing the fruit to continue to grow and develop red color
for an extended time.
Our experience in NJ is that ReTain reduces preharvest drop o McIntosh from
10-20%. Dr. Ed Stover, formally with Cornell University, Hudson Valley Lab,
says "McIntosh apples typically grow about 1% per day during the few
weeks around harvest. If we can delay harvest, we can take advantage of
additional fruit growth to produce a significantly higher proportion of
100 count fruit."
For varieties with narrow harvest windows like the scab resistant variety
Liberty, ReTain allows growers to delay harvest up to two weeks and pick
larger, more highly colored fruit that is firmer than untreated fruit.
Research in 1996 showed ReTain was also effective in reducing stem cracking
in Gala. This may be an added benefit. It will be interesting to see if
ReTain can help prevent cracking on Stayman as well.
In Washington State growers are excited about ReTain because of its ability
to enhance the storage quality of Red Delicious. In a 4000 bin pooled experiment,
2000 treated with ReTain and 2000 untreated, ReTain treated fruit treated
was 2lbs firmer allowing it to make export grade. NJ grown apples in regular
cold storage will see the same firmness enhancement with ReTain treated
fruit.
ReTain is a natural product which is very expensive to manufacture. Because
of this, ReTain should only be used in blocks with large crops of unblemished
fruit.
There are some important considerations to follow with ReTain applications
in New Jersey this year.
Use the full rate of ReTain, 1 pouch or 333 grams/Acre of formulated product
with an organosilcone surfactant at 0.10 % (v/v)
ONLY use one of the following organosilcone surfactant at surfactants:
Silwet L77 at 13 fluid ounces per 100 gallons
Sylgard 309 at 13 fluid ounces per 100 gallons
Apply 4 weeks before anticipated harvest (28 day PHI), it is better to apply
slightly earlier rather than later
Water Volume- ReTain should be applied with a sufficient amount of water
to ensure thorough wetting of the fruit while avoiding spray run-off. Adjust
water volume based on tree size and spacing
For optimum results apply during periods of slow drying weather conditions.
No rainfull or irrigation should occur within six hours of ReTain application
Do Not tank mix ReTain with other agricultural products
Do not apply NAA or ethephon products to ReTain treated blocks
For Pears: Contact your local Abbot Lab Ag Specialist or
call 1-800 323-9597 for specific information regarding the use of ReTain
on pears
ReTain is an exciting new harvest management tool for New Jersey growers.
Supply of this product is limited in 1997. Order your product now if you
hope to get some this season.
If you have specific questions regarding the use of ReTain please feel free
to contact me.