Table 5. Estimated volume (cubic yards) for the total number of pesticide containers generated by pesticide class. Dade County, Florida.

Paper n

Glass

Plastic II

Metal a

a

it

Size

^10#

>10#

lgal

lgal

5 gal

lgal 5 gal

30 gal

55 gal

Insecticide

44.6

145.8

11.6

81.9

365.1

22.0

633.4

103.4

165.1

Fungicide

251.4

123.0

0.1

33.4

77.9

13.7

13.8

0.2

0.0

Nematicide

0.7

10.2

0.0

0.0

0.0

0.0

32.1 152.6

0.0

Herbicide

7.0

12.1

0.5

52.8

1.9

3.4

17.3

6.7

0.0

Total

303.7

291.1

12.2

168.1

444.9

39.1

696.6

262.9

165.1

The 5 gal metal containers compose 696.6 cubic yards Selected References

and make up 29.2% of the total volume. The 5 gal metal I. Environmental Protection Agency. 1974 Pesticides and pesticide container is by weight and volume the biggest disposal containers; regulations for acceptance and recommended procedures problem. for disposal and storage. Federal Register. 39(85): 15235-15241.

2. . 1974 Pesticides; EPA proposal on disposal and storage. Federal Register 39(200):36847-36950.

3. Day, H. R. 1976. Disposal of dilute pesticide solutions. Environ

mental Protection Agency Report SW-519: 18 pp.

Proc. Fla. State Hort. Soc. 89:266-270. 1976.

EFFECTS OF PREHARVEST APPLICATIONS OF ETHEPHON AND SADH ON RIPENING, FIRMNESS AND STORAGE QUALITY

OF RABBITEYE BLUEBERRIES (cv. 'T-19')1

Elias D. Dekazos

USD A, Agricultural Research Service,

Richard B. Russell Agricultural Research Center,

Athens, Georgia 30604

Addition index words. (2-chloroethyl)phosphonic acid, suc-

cinic acid-2,2-dimethylhydrazide, blueberry storage, texture,

Vaccinium ashei.

A bstract. Succinic acid-2,2-dimethylhydrazide (SADH)

and/or (2-chloroethyl)phosphonic acid (ethephon) were ap

plied as preharvest fruit sprays to rabbiteye blueberries

(Vaccinium ashei Reade cv. T-19) at specific stages of berry

development. Fruit receiving ethephon treatments, regardless

of concentration, ripened significantly earlier than untreated

fruit. The multiple applications of ethephon, as well as the

application of SADH followed by ethephon, brought 95%

of the berries to full ripeness, reduced the length of the har

vest period by approximately 1 week, and had no significant

effect on the size of the berries.

The multiple applications of ethephon increased fruit

coloration without sacrificing firmness, reduced titratable

acidity, but had no significant effect on pH. SADH application

followed by ethephon resulted in highly-colored, firm fruits.

Storage quality of blueberries was maintained for 40 days—

a prolongation of their marketable life. The waxy bloom,

freshly harvested appearance, of the treated berries was re

tained throughout storage. Anatomical studies of treated

blueberry tissue showed that a relationship exists between

cell wall thickness and texture of sprayed berries.

lEthephon was supplied by Amchem Products, Inc., Ambler, Pa.,

and SADH by Uniroyal Chemical Division of Uniroyal, Inc., Nauga-

tuck, Conn.

Mention of growth regulators in this paper does not constitute a

recommendation for use by the U. S. Department of Agriculture.

Acknowledgement is given to Ruel Wilson, Biometrician, for sta

tistical analyses of the data.

266

Recent pomological studies include the introduction of

growth regulators for modifying fruit quality and ripening

behaviour (16). The growth regulator succinic acid-2,2-

dimethylhyrazide (SADH) was found to delay ripening of

apples (14), advance maturity and improve fresh color of

peaches (1) and sour cherries (19).

Fruit culture was further expanded by the use of (2-

chloroethyl)phosphonic acid (ethephon). This growth regu

lator accelerates color development and advances fruit ma

turity of prunes (17), peaches (18), cherries (2), pears (9)

and 'Mclntosh' apples (7, 15).

Eck (6) showed that applications of ethephon to highbush

blueberries hastened fruit ripening, increased percentage of

fruit ripe at first harvest, and produced smaller berries.

Ismail (11) reported that preharvest treatments with SADH

had no effect on the ripening rate of lowbush blueberry

fruit; whereas, ethephon accelerated berry ripening and

abscission. The application of ethephon to highbush blue

berries was reported by Howell et al. (10) to reduce fruit re

moval force which facilitated mechanical harvesting, to en

hance color development and hasten abscission.

Rabbiteye blueberries (Vaccinium ashei Reade) are

native to the Southeastern United States and have recently

received much attention and are of great interest as they

represent a cash income in developing rural areas in the

South. Large variability in fruit maturation of rabbiteye

blueberries occurs among the various varieties. The range of

3 to 5 weeks for the harvest period of individual varieties

presents a severe mechanical harvesting problem. If the

blueberry could be made to ripen most of its fruit for a

single harvest, an increase in the effectiveness of the mechan

ical harvesters would be realized.

The objective of this study was to determine the effect of

multiple applications of ethephon and the interaction of

SADH and ethephon on advanced and concentrated ripen

ing, fruit quality, anatomical structure of the cells and the

response of fruit during storage of rabbiteye blueberries.

Proc. Fla. State Hort. Soc. 89: 1976.

Materials and Methods

Evaluation of fruit quality. The rabbiteye blueberry

plants (cv. 'T-19') were grown commercially in Alma, Geor

gia. These plants were 5 years old, of the same size and

vigor. Solutions of SADH and/or ethephon with 0.05%

Tween-20 surfactant were applied to the fruit and foliage.

The experiment consisted of 5 treatments which were as

follows: A. 500 ppm SADH on May 20 and June 3, 1975;

B. 500 ppm SADH on May 20, 1975, followed by 500 ppm

ethephon on June 3 (SADH-ethephon); C. 500 ppm

ethephon on May, 20 and June 3, 1975; D. 1000 ppm

ethephon on June 3, 1975; and E. unsprayed control. Ap

plications of sprays on May 20 and June 3 correspond with

the 2 stages of fruit development, when berries were pink

(primarily pink coloration and green scar) and all purple.

Since no growth measurements were made to establish a

reference control growth curve, the double sigmoid growth

and development curve reported for blueberries by Young

(20) was used and spray applications were made at approxi

mately the middle of Period II and the beginning of Period

III of this curve. Treatments were applied to 4 plant-replica

tions using a randomized complete block design. Maturity

and harvest were based on color development (4) rather

than on the traditional fruit maturity indices such as sugar

content or total acidity.

Four pints of berry samples were harvested from each

bush on June 13, 1975. One sample from each plant was

analyzed at time of harvest for various quality parameters.

The remaining samples were placed in storage at 37°F (3°C)

and 95+% relative humidity and periodically examined.

After 40 days samples were removed and equilibrated to

room temperature prior to evaluation. Quality parameters

measured were as follows: size, expressed as number of ber

ries per 100 g weight; color, measured by the Hunterlab

Color and Color Difference Meter, model D25DM, with an

L, a, b readout and 5 cm diam specimen area, values given

represent an average of 4 measurements for each treatment;

firmness, measured by the Instron Universal testing ma

chine, model TM-SM with crosshead speed of 50 cm/min

and recording strip-chart speed of 100 cm/min with a 2-kg

full scale load, the values given for each treatment represent

an average of 4 measurements; titratable acidity (as %

citric acid), measured by titrating a blended fruit sample to

pH 8.1 with 0.1 N NaOH using a Beckman automatic titra-

tor; pH measured with a Beckman pH meter, model 1019;

soluble solids, determined with an Abbe L. Refractometer.

For firmness measurements, fruit was sorted for uniformity

and stage of ripeness into 4 replications of 5 berries each.

These berries were penetrated with a cherry pitting probe

mounted on the crosshead, and a puncture-force curve was

recorded by the machine. The total area under the curve

(work) was chosen because this gave the best representation

of the sample texture. The integrated readings were ex

pressed directly in the units of work.

Anatomical studies. Blueberry tissue was fixed in cold

formalin-acetic acid-alcohol (FAA), dehydrated through an

ethyl alcohol-TBA series, embedded in Paraplast, sectioned

at 20(u and stained with safranin and fast green (12). An

ocular micrometer was used for measuring the thickness of

the cell walls. Microscopic examinations were made with the

Leitz Orthoplan Research Microscope, and photomicro

graphs were obtained by using an Orthomat 2 camera.

Evaluation of keeping quality. Samples of berries har

vested June 13, 1975, and stored at 37°F and 95+ % R. H.

were removed after 40 days and the quality parameters were

measured as previously described. In addition berries were

separated into "marketable*', those that were attractive and

firm and considered sound; and "deteriorated", those that

had evidence of mold growth (decay), shriveled, and leaked

(either naturally or when the berry was rolled between the

fingers). The physical characteristics were scored by weight

and calculated as a percentage of the orignal weight before

storage.

Results and Discussion

Effects of sprays on blueberry ripeness and quality. All

fruit receiving ethephon treatment(s), regardless of concen

tration, ripened significantly earlier than the untreated

fruit. On June 3 it was visibly evident that the ethephon

sprayed plants had a percentage of blue berries while berries

on the control plants were practically all green. No symp

toms of phytotoxicity were observed.

Applications of ethephon and of SADH-ethephon

brought about 95% of the berries to full ripeness on the

date of harvest (June 13) while control bushes yielded only

36% on that date (Table 1). The treatments not only ad-

Table 1. Influence of SADH and/or ethephon on yield, size, color, firmness and chemical characteristics of 'T-19' rabbiteye blueberries, June 13

harvest.

Treatment &

dates of

application

Control

SADH (500 ppm

May 20 &

June 3)

% 1st harvest

June 13

36c*

44b

Number

berries/

100 g

59.0

65.5

L

20.85b

20.98b

Hunter

a

4- 0.38a

+ 0.40a

color values

b

-2.89c

-3.12bc

b/a

-7.61c

-7.80c

Texture

(puncture-

force)

gm-cm

3.40xl03cd

3.60xl03b

pH

3.28

3.26

Soluble

solids

(%)

14.0bc

13.9c

Titratable

acidityy

(%)

.90b

1.10a

SADH (500 ppm

May 20)

followed by

Ethephon (500

ppm June 3)

95a 59.5 21.70a 40.39a -3.71a -9.51a 3.78xlO3a 3.37 16.1a .69e

Ethephon (500

ppm May 20

& June 3)

95a 61.0 20.90b + 0.41a -3.40b -8.29b 3.50xl03bc 3.30 14.4b .81c

Ethephon (1000

ppm June 3) 95a 66.2 21.89a + 0.40a -3.42ab -8.55b 3.32xlO3d 3.32 13.8c .76d

"Means within a column followed by different letters are significantly different at the 5% level.

yAs percent citric acid.

Proc. Fla. State Hort. Soc. 89: 1976. 267

vanced maturity but also reduced the length of the harvest

period by approximately 1 week. The ethephon spray also

accelerated fruit abscission (point of release primarily

found at the junction of the fruit and pedicel) as was ob

served on the day of harvest when a few over-ripe berries

were found on the ground underneath the sprayed bushes

while no berries were found underneath the untreated or

the SADH-treated plants. The ethephon application of 1000

ppm was equally effective in bringing about an early ripen

ing period.

Fruit size was not significantly affected by the double ap

plications of ethephon or the SADH-ethephon treatment

when compared to the unsprayed fruit (Table 1); however,

the double SADH application and the high ethephon appli

cation resulted in a significant reduction in berry size.

Fruit color was significantly increased by either ethephon

or SADH-ethephon applications (Table 1). The effects of

SADH and ethephon on fruit coloring seem to be additive.

This can be seen by considering SADH alone which in

creased blue color by 7.4%, ethephon alone by 15.0%, and

SADH-ethephon by 22.1% relative to the unsprayed plants

(control). This shows that the SADH application signif

icantly aids in color development. The SADH alone had no

significant effect on fruit coloration.

An example of a puncture-force curve obtained for a

single blueberry is shown in Fig. 1. The puncture-force

curve obtained for a 5-berry sample is illustrated in Fig. 2.

The peaks produced in the curves indicate the puncture-

force required to break through the skin, penetrate the flesh

and the total resistance to puncture. Values for total punc

ture-force varied from 3.4 x 103 gm-cm for control to 3.78 x

103 for the SADH-ethephon berries (Table 1).

Enhancement of fruit firmness by SADH and a slight re

duction of same by 1000 ppm ethephon was observed (Table

1). Double applications of ethephon enhanced color without

sacrificing firmness. The application of SADH-ethephon

yielded fruit with the best firmness which means that there

is some interaction between these compounds.

There was no effect of SADH or ethephon on pH or

soluble solids (Table 1) as has been reported earlier in rela-

Fig. 1. Instron puncture-force curve of rabbiteye blueberry fruit.

Two peak curve showing the puncture-force required to break through

the skin and maximum force required to penetrate the fruit.

268

Fig. 2. Puncture-force curves produced by the Instron recorder re

sulting from tests on five rabbiteye blueberry fruits (cv. 'T-19').

tion to ethephon (10). Titratable acidity was reduced by

ethephon and appeared to be related to it. SADH signif

icantly increased acidity. The SADH-ethephon treatment

showed the greatest increase in soluble solids and decrease in

titratable acidity. Thus, the optimum conditions for ad

vanced and concentrated ripening, with less effect on fruit

size and quality improvement are the multiple applications

at low concentration of ethephon and the SADH-ethephon

treatment.

Anatomical observations. Significant anatomical changes

were observed in the cell wall thickness and size of the cells.

The cell walls of the control were not as thick as those of

SADH, ethephon, or SADH-ethephon treated tissue. Cell

size was larger in the treated tissue than in the control. This

is rather due to the ethephon effect. Ethephon produces

ethylene under acidic conditions. Burg and Burg (3) and

Goeschl et al. (8) have shown that ethylene promotes cell

enlargement. Cell wall thickness of the control tissue was

1.5 /a at 400x, while the ethephon treated mesocarp tissue

was approximately double in thickness and that of the

SADH-ethephon was about 3 times thicker than the control

(Fig. 3). The increased cell wall thickness seems to be related

to increased firmness. Each of the many textural qualities

may be the result of combined factors. Dekazos and Worley

(5) reported earlier that SADH-treated sour cherries had

more total wall material (thicker cell walls) and that a rela

tion between changes in cell wall polysaccharides and in

creased firmness resulted from the treatment.

Effects of spray on blueberry storage quality. Firmness of

berries stored at 37°F and 95+% R. H. for 40 days was

greatly influenced by preharvest growth regulator treat

ments. The SADH-ethephon treatment drastically sup

pressed the rate of softening of stored berries (Table 2).

SADH imparts the firmness advantage.

The acid content was increased by treatment and storage

with SADH. Postharvest changes indicated a slight increase

in soluble solids during storage.

The important quality characteristic of the natural waxy

bloom which gives the appearance of freshly harvested blue

berries was retained after 40 days storage by the fruit

sprayed with SADH and/or ethephon, but not by the con

trol berries (Fig. 4). Furthermore, the Hunter negative "b"

values which measure blueness were significantly higher for

all treated berries than for the control. The positive "a"

values measure redness, and they all decreased during stor

age. Therefore, the "b/a" values of the stored fruit were

practically doubled those of the fresh berries without any

great change in the correlation pattern. In addition the "L"

values which measure lightness or darkness were considera

bly lower for the control meaning that these berries were

darker than the treated (Table 2 and Fig. 4). The observa

tion that berries sprayed prior to harvest with SADH and/or

ethephon failed to darken as much as the control during

storage may have been due, at least in part, to the reduction

of polyphenoloxidase activity (13).

The greatest percentage of marketable fruit after 40 days

of storage was obtained from the SADH-ethephon treated

berries and the double ethephon treated (Table 2). It was

Proc. Fla. State Hort. Soc. 89: 1976.

Fig. 4. The 'T-19' blueberries treated with ethephon (E) and with SADH-ethephon (AE) retained their waxy bloom after 40 days storage

while it was completely lost for the control (C).

Fig. 3. Parenchyma cells of the 'T-19' rabbiteye blueberry mesocarp tissue showing A—untreated tissue, B—ethephon treated tissue, and C—the

thicker cell walls in the SADH-ethephon treated tissue. X125.

observed that ethephon treated berries had less mold (pre

dominantly Botrytis cinerea Pers.). Perhaps ethephon has

some effect on mold reduction. The effect of SADH and/or

ethephon was positive in extending storage life.

Differences noted at harvest in "ripeness"—mainly color,

firmness and other quality parameters—were retained to a

considerable extent in the 40-day stored berries. An informal

taste panel indicated a preference for the ethephon and

SADH-ethephon treated berries because of their superior

taste; appearance, retention of natural bloom; and texture,

like fresh berries. Waxy bloom in blueberries is an impor

tant quality characteristic that makes them desirable to the

consumer. The control berries were found to have an "off-

flavor", with darker appearance and mealiness.

The double applications of ethephon and the applica

tion of SADH-ethephon have imparted some important ad

vantages to the cv. 'T-19' of the rabbiteye blueberries. En

hanced color attributable to ethephon or SADH-ethephon

should advance and concentrate fruit ripening, a distinct ad

vantage for mechanical harvesting. The improved fruit tex

ture obtained from the application of SADH-ethephon will

not only be an asset to immediate fresh market acceptability

but will also enhance storage life of the fruit.

Literature Cited

1. Baumgradner, R. A., G. E. Stembridge, L. O. Van Blaricom and

C. E. Gambrell, Jr. 1972. Effect of succinic acid-2,2-dimethyl-

hydrazide on the color, firmness and uniformity of processing

peaches. /. Amer. Soc. Hort. Sci. 97:485-488.

2. Bukovac, M. J., E. Zucconi, R. P. Larsen and C. D. Kesner. 1969.

Chemical promotion of fruit abscission in cherries and plums with

special reference to 2-chloroethylphosphonic acid. /. Amer. Soc.

Hort. Sci. 94:226-230.

3. Burg, S. P. and E. A. Burg. 1966. Interaction between auxin and

ethylene and its role in plant growth. Proc. Natl. Acad. Sci. 55:262-

269.

4. Dekazos, E. D. and G. S. Birth. 1970. A maturity index for blue

berries using light transmittance. /. Amer. Soc. Hort. Sci. 95:610-

614.

Table 2. Influence of SADH and/or ethephon on color, firmness, chemical characteristics and storage life of 'T-19' rabbiteye blueberries after 40

days at 37°F and 95 + % relative humidity.

SADH (500 ppm

May 20)

followed by

Ethephon (500

ppm June 3)

Treatment &

dates of

application

Control

SADH (500 ppm

May 20 &

June 3)

L

18.70c*

20.67b

Hunter

a

+ 0.18b

+ 0.25a

color values

b b/a

-2.51d -13.74bc

-3.01c -12.04c

Texture

(puncture-

force)

gm-cm

1.60xl03c

2.20xl03a

pH

3.15

3.10

Soluble

solids

\/o)

14.2c

14.1c

Titratable

acidity7

(%)

.84b

1.03a

Deteriorated

fruit

(%)

24.15

12.50

Marketable

fruit

(%)

70.35c

85.00b

21.63a + 0.18b -3.62a -20.10a 2.39xlO3a 3.27 16.3a .65d 3.25 94.25a

Ethephon (500

ppm May 20

& June 3)

20.54b + 0.20b -3.25b -16.25b 1.88xlO3b 3.18 14.7b .76c 3.45 93.55a

zMeans within a column followed by different letters are significantly different at the 5% level.

yAs percent citric acid.

Proc. Fla. State Hort. Soc. 89: 1976. 269

5. and J. F. Worley. 1970. Effect of succinic acid-2,2-di-

methylhydrazide on anthocyanin metabolism and cell wall carbo

hydrates in red tart cherries, Prunus cerasus L., cv. Montmorency.

/. Amer. Soc. Hort. Sci. 95(6):703-706.

6. Eck, P. 1970. Influence of ethrel upon highbush blueberry fruit

ripening. HortSci. 5:23-25.

7. Edgerton, L. J. and G. D. Blanpied. 1970. Interaction of succinic

acid-2,2-dimethylhydrazide, 2-chloroethylphosphonic acid and auxins

on maturity, quality and abscission of applies. /. Amer. Soc. Hort.

Sci. 95:664-666.

8. Goeschl, J. D., L. Rappaport and H. K. Pratt. 1966. Ethylene as a

factor regulating the growth of pea epicotyls subjected to physical

stress. Plant Physiol. 41:877-884.

9. Griggs, W. H., B. T. Iwakiri, R. B. Fridley and J. Mehlschau. 1970.

Effects of 2-chloroethylphosphonic acid and cycloheximide on ab

scission and ripening of 'Bartlett' pears. HortSci. 5:264-266.

10. Howell, G. S., B. G. Stergios, S. S. Stackhause, H. C. Bitterbender

and C. L. Burton. 1976. Ethephon as a mechanical harvesting aid

for highbush blueberries (Vactinium australe Small). /. Amer. Soc.

Hort. Sci. 101:111-115.

11. Ismail, Amr A. 1974. Preharvest application of ethephon and SADH

on ripening and quality of lowbush blueberry fruit. HortSci. 9:205-

206.

12. Jensen, W. A. 1962. Botanical Histochemistry. W. H. Freeman &

Co., San Francisco and London.

13. Knapp, F. W., C. B. Hall, D. W. Buchanan and R. H. Biggs. 1970.

Reduction of poiyphenoloxidase activity in peaches sprayed with

alar, ethrel, or gibberellic acid. Phytochem. 9:1453-1456.

14. Looney, N. E. 1967. Effect of N-dimethylaminosuccinamic acid on

ripening and respiration of apples. Can. J. Plant Sci. 47:549-553.

15. . 1971. Interaction of ethylene, auxin and succinic acid-

2,2-dimethylhydrazide in apple fruit ripening control. J. Amer. Soc.

Hort. Sci. 96:350-353.

16. . 1973. Control of fruit maturation and ripening with

growth regulators. Acta Horticulturae 34:397-406.

17. Proebsting, E. L., Jr. and H. H. Mills. 1969. Effect of 2-chloroethane

phosphonic acid and its interaction with gibberellic acid on quality

of 'Early Italian' prunes. J. Amer. Soc. Hort. Sci. 94:443-446.

18. Rom, R. C. and K. R. Scott. 1971. The effect of 2-chloroethyl

phosphonic acid (Ethephon) on maturation of a processing peach.

HortSci. 6:134-135.

19. Unrath, C. R., A. L. Kenworthy and C. L. Bedford. 1969. The ef

fect of Alar, succinic acid-2,2-dimethylhydrazide on fruit maturation,

quality and vegetative growth of sour cherries, Prunus cerasus L.,

cv. 'Montmorency'. /. Amer. Soc. Hort. Sci. 94:387-391.

20. Young, R. S. 1952. Growth and development of the blueberry fruit

(Vractinium corymbosum L. and V. angustifolium Ait.). Proc. Amer.

Soc. Hort. Sci. 59:167-172.

Proc. Fla. State Hort. Soc. 89:270-271. 1976.

CHEMICAL THINNING OF 'SUNGOLD' NECTARINE1

T. E. Crocker, D. W. Buchanan and Peter Andersen

IF AS Fruit Crops Department,

G 199 McCarty Hall,

University of Florida,

Gainesville, FL 32611

Additional index words, ethephon, CGA 15-281, Prunus

persica.

Abstract. 'Sungold' nectarine trees were sprayed March

29, 1976 with 125, 250 and 550 ppm CGA 15-281 (Ciba-

Geigy Corp.) using 60 ppm ethephon [(2-chloroethyl) phos

phonic acid] as a comparison. Eethephon and 500 ppm CGA

gave the highest percentage of fruit removal, although the

former resulted in more uniform tree thinning.

Fruit thinning is one of the most important and costly

tasks of peach production in Florida. Peach growers in Flor

ida spend from $.75 to $2.00 per tree to hand-thin peaches

and nectarines. Most of the thinning is done by hand with

some fruit removed by limb shakers. Because of the cost and

time required for hand thinning, there is a pressing need for

a chemical thinning agent that would give uniform fruit

removal without excessive tree damage or reduced flower

bud development and fruit set the following year. Various

chemical-thinning chemicals have been tried (1, 2, 3, 4, 5),

but there has always been some adverse tree reaction to the

material that made these unsuitable as thinning agents. A

bloom thinner is not acceptable in the eastern U.S. due to

iFlorida Agricultural Experiment Station Journal Series No. 188.

270

the danger of frost at this time of year; therefore, such ma

terials have not been released for commercial use.

Ethephon as a comparison and CGA 15-281 were applied

to 'Sungold' nectarine to evaluate the amount of fruit re

moval and the effect of the chemicals on the trees.

Materials and Methods

A completely randomized block design using 5 single-tree

replications of Prunus persica 'Sungold' were selected for

each treatment. Treatments consisted 125, 250 and 500 ppm

CGA 15-281, with 60 ppm ethephon as a comparison. The

number of fruit on 1 limb in the N, S, E and W quadrants

were counted and recorded for each tree and the limbs

marked with yellow tape. Chemicals were applied on March

29, 1976, which corresponded to cytokinesis (12 mm seed

length) (6). Chemicals were diluted in the field and applied

to drip on the trees with a small power sprayer.

The amount of fruit removed was determined by count

ing the number of fruit remaining on each of the tagged

limbs April 21. The trees were then observed until normal

harvest and later for any adverse effect of the chemicals on

foliage and fruit growth or deformity.

Results and Discussion

A significantly larger number of fruit (Fig. 1) was re

moved with the ethephon and 500 ppm CGA 15-281 than

with either 125 and 250 ppm CGA 15-281. There was no sig

nificant difference between ethephon and 500 ppm CGA 15-

281.

Ethephon gave a consistent fruit removal, with the dif

ference among the 5 trees being only 8% (Table 1). This

Proc. Fla. State Hort. Soc. 89: 1976.