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Level of thinning by cultivar
Easy to Thin
Intermediate to thin
Difficult to thin

You can also use 3-5 ppm NAA at petal fall and follow up at 8mm with 1qt of Sevin/A if Needed.

All the above petal fall treatments allow for you to come back with a second application of the
appropriatematerial at 8-10MM. Also a third applications is possible with the use of Ethephon in the
late fruit set window of 12-18mm. Ethephon can be used up to 25mm as a last resort.

A second approach might be to try using Sevin XLR at petal fall at 1 qt/A. It can be used alone or
combined with NAA. Combined with NAA it is more aggressive. Varieties like Gala are hard to thin
and will benefit from the multiple approach. Since Gala, Fuji, Golden Delicious and others are hard to
size and thin, be aggressive if bloom warrants at petal fall.

For Gala, time sprays based on bloom on the older wood, not one year old wood. Time the rate by
sizing the fruit on the older wood, i.e. 5-8mm for sprays later than petal fall. The goal is to thin off the
bloom on the one year wood, the fruit is always smaller on one year wood on Gala.

Golden Delicious: consider the use of Ethephon 2 (21.7%) at 1/2 pint per 100 gallons plus 10ppm of
NAA. Ethephon is labeled for Goldens. The label calls for an increased rate for spur Goldens. One
north Jersey grower has used this combination on Goldens for over 15 years with goo d success.

Fuji can be thinned successfully at petal fall according to reports from British Columbia, CA.
According to a report published in Compact Fruit Tree, Vol. 31 No1, April 98, Dr. Norm Looney
conducted two sets of experiments in 1995 and 1997 with Fuji. Carbaryl (Sevin) proved to be an
effective thinner of Fuji at petal fall. The addition of ACCELL enhanced the thinning effect and
appeared to improve return bloom.
For Jersey Reds try 5ppm NAA plus Sevin XLR at 1 quart/A, again this combinationhas been
successful in North Jersey consistently.
As you can see there are a lot of ways to go. Try some bloom and petal fall sprays, use
multiple applications. Keep detailed records including weather two days before and two days after
application. and always leave some check trees. Experiment slowly on portions of your acreage by

If you still have too much fruit after petal fall and 8-10 MM applications, consider the use of ethephon
or ethephon combinations.

A review of Chemical Choice for Apple Thinning

NAA- is one of our oldest and most reliable thinners. It can be applied from petal fall to 20MM fruit
size at rates of 5ppm to 20ppm per 100 gallons. It is especially effective in helping to return bloom.

Caution Note:on red delicious do not apply concentrations more than 5ppm to avoid pygmy
fruits. Do not use NAA or NAD on any trees that are to be treated with Accel, Promalin or
Provide this year! Pygmy fruit may result.

NAD- is a mild form of NAA and is used at PF and early fruit set only! It is very affective on summer
varieties such as Paulared, Jerseymac, Macintosh cultivars and Macoun. It is usually applied at 40-50
ppm per 100 gallons at PF-5MM. (See above caution)

1999 North Jersey Tree Fruit Annual Report