Title: Fruit Thinning and Return Bloom
1Fruit Thinning and Return Bloom
- Rongcai Yuan
- AHS Agricultural Research and Extension Center,
Virginia Tech
2Why Should We Thin Fruit?
- Increase fruit size / quality/fruit price
- Increase return bloom
- Maintain tree health, hardiness, and structure
- Chemical thinning is superior to hand thinning
- Earlier thinning gives best responses
- Less expensive
3Why can chemical thinners increase fruit size?
4Relation between fruit size and leaf number in
Delicious
Magness and Overley, 1931
5Fruit Size and leaf number in Stayman apples
6How Do Chemical Thinners Thin Apples ?
7What causes young fruit to set or abscise?
- Competition among young fruit for carbohydrates
and hormones - Competition between fruit and shoots
8Chemical thinners promote fruit abscission by
causing stresses
- NAA and BA reduce leaf Pn and reduce carbohydrate
supply. - NAA and BA also enhance ethylene production.
- Ethephon releases ethylene and promotes fruit
abscission.
96-BA on nonstructural carbohydrates levels of
McIntosh apple leaves
Yuan and Greene, 2000
10ReTain inhibited NAA-induced young fruit
abscission in Delicious apples-2007
Hong Zhu, 2007
11ReTain reduced NAA-induced expression of MdPG2
gene in Delicious
12Factors Affecting Chemical Thinning
13Chemical Thinners
- 6-BA, carbaryl, NAA, and ethephon
- Ethephon is temperature dependant.
- The combination of carbaryl and 6-BA or NAA is
much stronger than either alone. - NAA will cause pigmy fruit at low temperature (lt
70 oF). - NAA may cause pygmy fruit in Delicious if NAA
is applied at concentrations greater than 5 ppm
or applied when fruit size is larger than 10 mm. - NAA BA will cause pigmy fruit.
14Chemical thinner NAA may cause small and pygmy
fruit in Delicious
15Fruit Size
16(No Transcript)
17Effect of fruit size on fruit thinning of Golden
Delicious (2006)
a
NAA 4 oz Ethephon 1.5 pint Sevin XLR 1
pint Maxcel 2 pints Oil 4
pints Water 100 gal.
b
b
bc
c
c
Fruit size at application (mm)
18Effect of application date on fruit thinning of
Delicious/M26 in New York - 2007
NAA 3 oz Sevin XLR 1 pint Maxcel 3
pints Water 100 gal.
Courtesy of Dr. Robinson
19Effect of fruit size on fruit thinning of
Gala-2007
a
Ethephon 1.5 pint Sevin XLR 1 pint Maxcel 2
or 4 pints Oil 4 pints Water
100 gal.
b
20Fruit thinning on Gala fruit size
Sevin 6-BA
Control
21Summary
- Petal fall-7 mm Carbaryl
- 8-17 mm Carbaryl and NAA alone may effectively
thin apples, but the combination of carbaryl and
NAA or 6-BA is more aggressive than carbaryl,
6-BA, or NAA alone. - 18-28 mm Ethephon (1 to 1.5 pt/100 gal.) is
effective. - Carbaryl, 6-BA and NAA alone or in combination
have a slight or no effect. - 30 mm or bigger Ethephon has a slight or no
effect.
Special case Fuji gt18 mm, ethephon has no
thinning effect Gala gt18 mm, ethephon can
remove some fruit
22Temperature
- Effects of day and night temperature on the
efficacy of NAA in thinning apples when applied
at 10 mm stage of fruit development -
23NAA on Golden Delicious apple fruit thinning at
60/40 oF
24NAA on Golden Delicious apple fruit thinning at
70/50 oF
25NAA on Golden Delicious apple fruit thinning at
80/60 oF
26Summary
- 70 oF or higher is good for fruit thinning.
- 65 oF marginal for chemical thinners.
- lt60 oF too low for chemical thinners.
- NAA causes pigmy fruit at low temperature.
- Based on our field trials, the maximum air
temperature in the first 2 and 3 days after spray
is very important. More fruit thinning or
overthinning will be expected when maximum
temperature is gt85 oF in first 3 days after
spray. -
-
27Varieties
28Recommended fruit thinning programs
- Easy or moderate to thin varieties
- 1). Carbaryl (1 to 2 pt) oil (4 pt)/100
gal. - 2). NAA (2.1 to 4 oz)/100 gal.
- Hard to thin varieties such as Golden Delicious
- 1). 4-6 oz NAA/100 gal water
- 2). Carbaryl (1-2 pt) NAA (2.1 oz)
oil (4 pt)/100 gal - 3). Carbaryl (1 to 2 pt) 6-BA (2 pt)
oil (4 pt)/100 gal
- followed by ethephon (1.5 to 2 pt/100 gal.) when
fruit size is 18 to 28 mm.
29- For Fuji 1-2 pt Carbaryl 3-4 pt 6-BA 4 pt
oil/100 gal water. NAA will cause pygmy fruit. - For Gala 1).1-2 pt Carbaryl 2-3 pt 6-BA 4 pt
oil/100 gal water 2). 1-2 pt Carbaryl 2.1 3
oz. NAA 4 pt oil/100 gal water. - You need to increase the rate of 6-BA or NAA if
you do not add oil to the solution. - These rates are for dilute sprays. You need to
increase the rates accordingly if you do
concentrate sprays.
30Golden Supreme 6.4 mm
Average daytime high temperatures for the first
2 and 3 days after application were 63.2 and 65.8
oF.
31Effects of Sevin XLR and 6-BA on fruit thinning
of Red Delicious in 2007w
wFull bloom occurred on April 24, 2007. TRV was
200 gal./acre. xTreatments were applies with an
airblast sprayer. y Fruit/cm2 limb cross
sectional area was determined on June 14,
2007. zMean separation within column by Duncans
new Multiple Range Test.
32Delicious-2007
33Red Delicious-2008
Sevin 6-BA
Control
34Tree age and vigor
- Young trees are easier to thin than mature trees
because the competition between young fruit and
vegetative growth is more intense in young trees
than mature trees.
35Return Bloom
36Effect of ethephon at 200 ppm applied in on
years on flowering of Delicious
xEthephon was applied in 1998, 2000, and
2002 zBloom density ranging from 1 to 10
(highest).
Bukovac et al., 2006
37Effect of NAA and ethephon on flowering of York
apples-2007x
xTreatments were applied on 5/22, 6/5, 6/19, and
7/5/ 2006. zBloom density ranging from 1 to 10
(highest).
38Effect of NAA and ethephon on flowering of York
apples-2008
XTrees were treated with Sevin XLR 6-BA for
thinning.
39NAA ethephon on return bloom in York apples
Unthinned control
Thinned control
Chemical Thinning NAA ethephon
40Summary
- Ethephon and NAA alone can increase return bloom
in Red Delicious and Golden Delicious. - The combination of NAA and ethephon had better
effects than either alone in enhancing return
bloom in York apples.
41Acknowledgement
- David H. Carbaugh
- Amelia G. Engelman
- Virginia Apple Research program
- Virginia Agricultural Council
42THANK YOU !HAVE A GOOD YEAR!