F NORTH FLORIDA EXPERIMENT STATION
f IE5 Quincy, Florida
70 9 September 11, 1969
North Florida Station Mimeo Report NFES 70-2
Influence of succinic Acid 2,2-Dimethyl Hydrazide (Alar) on Fruit
Development of 4 North Florida Peach Varieties
J. B. Aitkenl/
In recent years the cost and availability of labor has prompted growers to seek ways
of reducing the amount of labor required to produce peaches in North Florida. The
possibility of mechanical harvesters in the future which would require uniform crop maturity
and the idea that uniform ripening would reduce the number of pickings stimulated a search
for a means of inducing uniform ripening.
In 1969, a study was initiated to determine what influence Alar would have on the fruit
development of peaches in North Florida. Alar was found to promote more uniform ripening
of peaches in South Carolina and pickings were reduced from 5 to 22/.
MATERIALS AND METHODS
Succinic acid 2,2-dimethyl hydrazide (Alar) was furnished by UniRoyal Chemical Div. of
UniRoyal Inc. as a 85% formulation.
Armgold, June Gold and Suwannee varieties were treated with 0, 500, 1000 and 2000 ppm
aqueous solution of Alar at stylar abscission and 4000 ppm 40 days before anticipated
harvest. Stylar abscission occurred about 40 days before anticipated harvest in Armgold and
June Gold. The June Gold and Suwannee experiments each had 3 replications of single-tree
plots of 5-year-old trees. The Armgold experiment consisted of 4 replications of single-
tree plots of 4-year-old trees.
An additional experiment was set up on 9-year-old Maygold trees replicated 3 times
using single-tree plots. This experiment involved a concentration x application date series
of treatments. Concentrations were 500, 1000, 2000 and 4000 ppm applied 5, 10, 15, 20, 25
'nd 30 days after full bloom. In addition 4000 ppm was applied 35 days after full bloom
(40 days before anticipate harvest). An untreated control was included in the experiment.
All of the experiments were arranged in a randomized complete block design for
Alar solutions in each experiment were applied as foliar sprays to run-off using a
-ortable pumping unit operating at 100 psi and applying 0.75-1.5 gallons of spray per tree
depending upon tree size. All sprays were applied in the morning with none of the sprays
being washed off the day of application.
Fruit weight was used as the index of treatment effect on Armgold and June Gold. All
fruit on each tree was harvested, counted and weighed in order to determine an average
:sight per fruit. The index used on Suwannee was fruit firmness as determined with a
-Assistant Professor (Assistant Horticulturist), North Fla. Expt. Sta., Quincy.
SE. T. Sims, Jr., Unpublished data, Clemson Univ., Clemson, S. C.
Magness Pressure Tester Model 30A equipped with a 7/16 inch plunger. Fruit weight and
firmness were determined on the concentration x application date experiment on Maygold
peach. The size of the Maygold experiment prohibited harvesting the entire tree so
approximately 1 bushel was harvested randomly from each tree. Limbs were selected at
random around the tree and all of the fruit on the limbs harvested. From each 1 bushel
tree sample, 30 fruit were randomly selected, weighed collectively, and firmness determined
on 15 of these at random.
All treatments were hand thinned at the proper stage of fruit development. Fruit in
all experiments was harvested at shipping maturity. A standard insect and disease spray
program was followed throughout the season consisting primarily of parathion and sulfur
and sulfur alone near harvest.
RESULTS AND DISCUSSION
The data in Table 1 indicate that Alar exerted little influence on the fruit weight of
Armgold and June Gold peaches. However, the 500 and 1000 ppm rates tended to increase
fruit weight above the control while the higher rates reduced fruit weight in comparison
with control. A considerable amount of leaf drop was noticed about 2 weeks after appli-
cation of the 4000 ppm indicating that this rate was probably phytotoxic to the Armgold
variety. The time of application appears to have been too late on these 2 varieties based
on pattern of fruit development.
All concentrations of Alar except 1000 ppm significantly decreased firmness on Suwannee
peach in comparison to the control (Table 2). Economically the 2000 ppm rate was as good as
4000 ppm and would require only half the amount of chemical.
The data in Table 3 indicate that several concentration x application date combi-
nations could be used to obtain the same end result. The lowest firmness value of 5.69
pounds was obtained with 1000 ppm applied 25 days after full bloom. The largest fruit by
weight was 1000 ppm applied 20 days after full bloom. The 1000 ppm rate applied 15 or 25
days after full bloom would probably be the best treatments to use commercially followed
by 500 ppm applied 15 days after full bloom.
Several of the 2000 and 4000 ppm treatments had low firmness values but the fruit
weight in most cases was lower than the control though not significantly lower. A firmness
value of 7.25 pounds and fruit weight of 107.80 grams was obtained by applying 4000 ppm 30
days after full bloom. Not all of the combinations have been listed but from an economical
standpoint it seems that either 500 ppm applied 15 days or 1000 ppm applied 15-25 days after
full bloom would be the most promising.
The data reported in this paper are based on 1 year of research on the influence of
Alar on fruit development of peaches. The rates used on Armgold and June Gold were
ineffective at the time they were applied. The use of 2000 ppm Alar on Suwannee peach
appears to be slightly better than 500 ppm. Application of 500 ppm 15 days after full
bloom or 1000 ppm 15-25 days after full bloom on Maygold peaches gave the greatest decrease
in fruit firmness with an accompanied increase in fruit weight. This study will be
continued another year on each of the varieties.
Table 1. Dates of stage of fruit development by varieties.
Stage of Fruit Variety
Development Armgold June Gold Maygold Suwannee
Full bloom 3-4-69 3-10-69 3-20-69 3-10-69
Stylar abscission 4-4-69 4-16-69 -- 4-16-69
40 days prior 4-4-69 4-16-69 4-23-69 5- 8-69
Harvest 5-14-69 4-23-69 6-3-69 6-16-69
Table 2. Effect of Alar on fruit
and June Gold peaches.
weight of Armgold
Fruit Weight, g
Concentration, ppm Armgold-/ June Goldl/
Control 40.84 ab 49.20 a
500 41.80 b 58.18 a
1000 43.35 b 56.71 a
2000 37.60 ab 49.66 a
4000 35.19 a 43.09 a
Means not having
different at the
a letter in common
Table 3. Effect of Alar on firmness
of Suwannee peach.
Control 28.93 c
500 22.97 ab
1000 26.43 bc
2000 21.07 a
4000 20.83 a
~ Means not having a letter in common
are significantly different at the
Table 4. Effect of Alar on fruit weight, fruit diameter and firmness
applied at 5 day intervals after full bloom.
of Maygold peach
Concentration, Days after Fruit Fruit
ppm Full Bloom Firmness, Ibs'/ weight, g- Diameter, cm2-
500 5 16.38 de 75.67 a 5.07
10 10.50 abc 92.61 abcde 5.65
15 8.46 abc 97.46 abcde 5.82
20 10.69 abc 76.12 a 5.09
25 11.85 bcd 95.85 abcde 5.76
30 8.71 abc 91.71 abcde 5.62
1000 5 9.90 abc 82.33 abc 5.30
10 9.64 abc 87.32 abcde 5.47
15 6.93 ab 94.43 abcde 5.72
20 10.35 abc 108.51 e 6.20
25 5.69 a 94.89 abcde 5.73
30 8.99 abc 87.92 abcde 5.49
2000 5 10.88 abc 77.03 a 5.12
10 8.43 abc 79.45 ab 5.20
15 10.36 abc 100.48 bcde 5.92
20 7.30 ab 70.75 ab 5.21
25 8.08 abc 103.66 cde 6.03
30 6.82 ab 85.96 abed 5.42
4000 5 10.56 abc 86.41 abcd 5.44
10 7.27 ab 91.10 abcde 5.60
15 8.16 abc 79.75 ab 5.21
20 8.95 abc 85.95 abcd 5.42
25 9.19 abc 95.34 abcde 5.75
30 7.25 ab 107.80 de 6.17
35 12.49 cd 100.94 bcde 5.94
Control 17.69 e 82.93 abc 5.32
l/Within each column,
different at the 5%
any 2 means not having a letter in common are significantly
2/Fruit diameter determined from standard curve based on fruit weight.