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Gulf Coast Research
and Education Center
5007 60th St. E., Bradenton, Florida 34203-9324
Centra, Sc e ice
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GULF COAST RESEARCH & EDUCATION CENTER
IFAS, UNIVERSITY OF FLORIDA
5007 60th Street East
Bradenton, FL 34203
Bradenton GCREC Research Report BRA1992-4 March
FRUIT SET AND YIELD OF WATERMELON
1. Fruit Set Experiment
2. Bee Attractant Experiment
D. N. Maynard'
Standard watermelons represent most of the commercial crop grown in Florida.
Icebox and seedless watermelons also are grown in Florida. Florida produced 9
million cwt of watermelons from 45,000 harvested acres in 1989-90 which provided
an average yield of 200 cwt/acre. The average price was $7.15/cwt providing a
crop value of $64,350,000 which accounted for 4.9% of the gross returns to the
state's vegetable growers (Freie and Young, 1991).
The efficacy of BeeScent for watermelon pollination was previously evaluated in
Florida (Elmstrom and Maynard, 1990). Total yield was increased on one of three
farms in central Florida and there was an apparent increase in early yield at all
three farms in southwest Florida. Fruit soluble solids were not affected by
treatment, but seed content of fruit from three of five farms increased.
The purpose of these experiments was to determine the fruit setting pattern of
four watermelon varieties and to further evaluate the efficacy of BeeScent for
enhancement of watermelon fruit set.
MATERIALS AND METHODS
Fruit Set Experiment. Soil samples from the experimental area obtained before
fertilization were analyzed by the IFAS Extension Soil Testing Laboratory (Hanlon
and DeVore, 1989): pH = 6.4 and Mehlich I extractable P = 20, K = 60, Mg = 116,
Ca = 684, Zn = 2.4, Cu = 0.6, Mn = 0.9 ppm.
The EauGallie fine sand was prepared in late August 1991 by incorporation of 0-
1.2-0 lb N-P,0s-K20 per 100 linear bed feet (Ibf). Beds were formed and
fumigated with methylbromide:chloropicrin 67:33 at 2.3 lb/100 1bf. Banded
fertilizer was applied in shallow grooves on the bed shoulders at 2.5-0-3.4 lb
N-P20-KO0 per 100 Ibf after the beds were pressed and before the white
polyethylene mulch was applied. The total fertilizer applied was equivalent to
120-60-167 lb N-P205-KO0 per acre. The final beds were 32 in. wide, 8 in. high,
and were spaced on 9 ft centers. There were four beds between seepage
irrigation/drainage ditches which were on 41 ft centers. 'Mickylee', 'Jubilee
II', 'Sangria' and 'King of Hearts' seeds were planted in peat-lite growing mix
in Todd planter flats (1.5 x 1.5 x 2.5 in. cells) on 12 August. The watermelon
transplants were grown by a commercial plant grower.
'Professor of Vegetable Crops and Extension Vegetable Specialist.
The transplants were field planted on 10 September in holes punched in the
polyethylene mulch at 3 ft in-row spacing. The 57 ft long plots each had 19
plants and were replicated four times in a randomized complete block design.
However, the triploid variety 'King of Hearts' was always in one of the center
two beds to insure adequate pollination from diploid pollenizers on either side.
Weed control in row middles was by cultivation and applications of paraquat.
Pesticides were applied as needed for control of sweetpotato whitefly endosulfann
and esfenvalerate), aphids endosulfann) and gummy stem blight (chlorothalonil).
From 30 September to 18 October all open pistillate flowers were marked with
dated tags. The watermelons were harvested on 19 and 26 November and 5 December.
Marketable melons (U.S. No. 1 or better) according to USDA Standards for Grades
(USDA, 1978) were separated from culls and counted and weighed individually.
Soluble solids determinations were made with a hand-held refractometer on 24
fruit of each variety over three harvests. The resulting data were subjected to
analysis of variance and mean separation was by Duncan's multiple range test.
Bee Attractant Experiment. Four plot areas 200 ft long and 20 ft wide (four
beds) were marked off in a commercial field of 'Sangria' watermelons located off
of Rye Rd, Manatee County. A bee attractant, BeeScent (Scentry, Inc., 610
Central Ave., Billings, MT 59102), was applied on plants in two plots with a
backpack sprayer at 2 qts per acre on 2 October at early pistillate bloom stage
and again on 9 October at full pistillate bloom stage. Two additional plots were
not treated. Before harvest, the plots were subdivided resulting in four 100 x
20 ft treated and four untreated replicates.
The watermelons were harvested by a commercial crew on 10 and 19 December. Each
melon was counted and weighed individually. The resulting data were subjected
to analysis of variance.
RESULTS AND DISCUSSION
Fruit Set Experiment. Temperatures during the experimental period were slightly
higher than normal in September and October and a little below normal in November
(Table 1). During the experimental period, rainfall was less than for the 38-
The number of watermelon fruit that matured to harvest were set mainly between
7 and 10 October (Table 2). Likewise, a high proportion of open flowers set
fruit on those days. Although pistillate flowers first appeared on 30 September,
no fruit set was noted until 7 October. Pistillate flowers were produced at
about the same rate on 14-15 October as during the 7-10 October period, yet very
low fruit set was noted. The reason for this pattern of fruit set is not known.
However, high day (average 890F) and night (72 F) temperatures prevailed from 30
September to 4 October, whereas day temperatures averaged 850F and night
temperatures averaged 660F during the 7-10 October period when fruit set
occurred. The failure of fruit set after 10 October is attributed to the well-
known effect of earlier fruit set on subsequent fruit set in the Cucurbitaceae.
During the period between 30 September and 18 October, 17% of the 'Jubilee II'
and 'King of Hearts' flowers set fruit, whereas 20% of the 'Mickylee' and
'Sangria' flowers set fruit. 'King of Hearts' and 'Mickylee' plants produced
about twice as many pistillate flowers as 'Jubilee II' and 'Sangria' plants.
Table 1. Mean temperature and rainfall
Center from 10 September to 5
averages (Stanley, 1992).
at the Gulf Coast Research & Education
December 1991 and 38-year monthly
Average daily temperature (oF)
1991 38-yr averages Rainfall (in.)
Month (date)' Max. Min. Max. Min. 1991 38-yr averages
September (10-30) 92 72 90 71 0.52 8.28
October 87 66 85 64 1.21 2.80
November 78 55 79 57 0.06 2.01
December (1-5) 81 59 73 51 0.42 2.33
'1991 data are for the dates shown; 38-year averages are for the entire month.
Table 2. Number of watermelon fruit set per day and percent of flowers that
set fruit between 30 September and 18 October. Fall 1991. Gulf
Coast Research and Education Center.
Jubilee II King of Hearts Mickylee Sangria
Date (No.) (%) (No.) (%) (No.) (%) (No.) (%)
30 September 0 c 0 c 0 c 0 c 0 c 0 d 0 c O b
01 October 0 c 0 c 0 c 0 c 0 c 0 d 0 c 0 b
02 October 0 c 0 c 0 c 0 c 0 c 0 d 0 c 0 b
03 October 0 c 0 c 0 c 0 c 0 c 0 d 0 c O b
04 October 0 c 0 c 0 c 0 c 0 c 0 d 0 c 0 b
07 October 6 b 31 a 12 a 40 a 14 b 53 a 7 a 41 a
08 October 9 a 22 ab 12 a 39 a 21 a 38 b 7 a 34 a
09 October 3 c 16 b 7 b 28 ab 7 c 33 b 2 b 12 b
10 October 2 c 14 bc 6 b 21 b 4 cd 14 c 2 b 10 b
14 October 0 c 1 c 3 c 8 c 0 c 0 d 1 b 2 b
15 October 0 c 3 c 0 c 4 c 0 c 2 d 0 c 2 b
16 October 0 c 0 c 0 c 0 c 0 c 3 d 0 c 0 b
18 October 0 c 0 c 0 c 0 c 0 c 0 d I b 10 b
'Mean separation in columns by Duncan's multiple range test, 5% level.
The high number of flowers produced by 'King of Hearts' and 'Mickylee' relates
to the significantly greater number of fruit produced per acre compared to
'Jubilee II' and 'Sangria' (Table 3). Highest yields were produced by 'King of
Hearts' at 607 cwt per acre and 'Jubilee II' produced the lowest yields at 480
cwt per acre. Average fruit weight varied from 7.6 lb for 'Mickylee' to 16.1 lb
for 'Jubilee II'. Fruit weight was lower than that obtained in spring trials,
perhaps because watermelon growth is better in the spring than in the fall
because of more favorable temperatures and daylength. Soluble solids ranged from
9.7% in 'Jubilee II' to 12.4% in 'King of Hearts'. With the exception of
'Jubilee II', soluble solids exceeded the 10% specified for optional use in the
U.S. Standards for Grades of Watermelons (USDA, 1978).
Table 3. Yield, average fruit weight, and soluble solids of watermelons.
Fall 1991. Gulf Coast Research and Education Center.
Yield/A Avg. fruit Soluble
Entry No. Cwt Wt (Ib) Solids
Jubilee II 2993 c' 480 c 16.1 a 9.7 d
King of Hearts 5794 b 607 a 10.5 c 12.4 a
Mickylee 7259 a 545 b 7.6 d 10.6 c
Sangria 3545 c 526 b 14.9 b 11.1 b
'Mean separation in columns by Duncan's multiple range test, 5% level.
Bee Attractant Experiment. Applications of bee attractant did not significantly
increase early and total yields or average fruit weight as compared to untreated
plots (Table 4). However, the numerical results favored application of bee
attractant in every case.
Table 4. Early and total yield and average fruit weight of
watermelons untreated and treated with Bee Scent.
Measurement Untreated Treated Significance'
No./A 446 539 NS
Cwt/A 97.6 117.2 NS
Avg. fruit wt (Ib) 21.7 21.7 NS
No./A 1683 1702 NS
Cwt/A 303.1 314.4 NS
Avg. fruit wt (Ib) 18.0 18.3 NS
1NS = not.significant at F test 5% level of probability.
Although these results do not show a significant advantage in the use of a bee
attractant, there may be circumstances where it would be advantageous as outlined
by Elmstrom and Maynard (1990), namely:
An inadequate number of beehives are present;
Available hives have low bee populations;
Death of bees from pesticide misuse;
Cold, windy, or overcast weather;
Competing crops or weeds are nearby;
Lack of adequate viable pollen;
Improved seed yield or quality is necessary; and
Reduced incidence of hollowheart is required
A high proportion of pistillate watermelon flowers set fruit between 7 and 10
October. Almost no fruit set before or after these dates even though there were
abundant pistillate and staminate flowers present. Fruit set during this period
may have been related to an average reduction in temperature of 4 F during the
day and 60F at night.
Applications of BeeScent at early and full pistillate flowering did not result
in increased early or total yields and average fruit weight, although there was
a numerical advantage to the use of the attractant.
The information contained in this report is a summary of experimental results and
should not be used as recommendations for crop production. Where trade names are
used, no discrimination is intended and no endorsement is implied.
Freie, R. L. and H. V. Young. 1991. Florida Agricultural Statistics. Vegetable
Summary. Florida Agricultural Statistics Service, Orlando.
Elmstrom, G. W. and D. N. Maynard. 1990. Attraction of honey bees to watermelon
with bee attractant. Proc. Fla. State Hort. Soc. 103:130-133.
Hanlon, E. A. and J. M. DeVore. 1989. IFAS Extension Soil Testing Laboratory
Chemical Procedures and Training Manual. Fla. Coop. Ext. Circ. 812.
Stanley, C. D. 1992. Temperature and rainfall report for 1991. GCREC Res. Rept.
U.S. Standards for Grades of Watermelon. 1978. U.S.D.A.
The Gulf Coast Research and Education Center
The Gulf Coast Research and Education Center is
a unit of the Institute of Food and Agricultural Sci-
ences, University of Florida. The Research Center
originated in the fall of 1925 as the Tomato
Disease Laboratory with the primary objective of
developing control procedures for an epidemic out-
break of nailhead spot of tomato. Research was ex-
panded in subsequent years to include study of sev-
eral other tomato diseases.
In 1937, new research facilities were established
in the town of Manatee, and the Center scope was
enlarged to include horticultural, entomological, and
soil science studies of several vegetable crops. The
ornamental program was a natural addition to the
Center's responsibilities because of the emerging in-
dustry in the area in the early 1940's.
The Center's current location was established in
1965 where a comprehensive research and extension
program on vegetable crops and ornamental plants is
conducted. Three state extension specialists posi-
tions, 16 state research scientists, and two grant
supported scientists from various disciplines of
training participate in all phases of vegetable and
ornamental horticultural programs. This interdisci-
plinary team approach, combining several research
disciplines and a wide range of industry and faculty
contacts, often is more productive than could be ac-
complished with limited investments in independent
The Center's primary mission is to develop new
and expand existing knowledge and technology, and
to disseminate new scientific knowledge in Florida, so
that agriculture remains efficient and economically
The secondary mission of the Center is to assist
the Cooperative Extension Service, IFAS campus
departments, in which Center faculty hold appropri-
ate liaison appointments, and other research centers
in extension, educational training, and cooperative
research programs for the benefit of Florida's pro-
ducers, students, and citizens.
Program areas of emphasis include: (1) genetics,
breeding, and variety development and evaluation;
(2) biological, chemical, and mechanical pest manage-
ment in entomology, plant pathology, nematology,
bacteriology, virology, and weed science; (3) produc-
tion efficiency, culture, management, and counteract-
ing environmental stress; (4) water management and
natural resource protection; (5) post-harvest physiol-
ogy, harvesting, handling and food quality of horti-
cultural crops; (6) technical support and assistance to
the Florida Cooperative Extension Service; and (7)
advancement offundamental knowledge ofdisciplines
represented by faculty and (8) directing graduate
student training and teaching special undergraduate
J The Institute of Food and Agricultural Sciences,
University of Florida.
" A statewide organization dedicated to teaching,
research and extension.
U Faculty located in Gainesville and at 13 research
and education centers, 67 county* extension
offices and four demonstration units throughout
" A partnership in food and agriculture, and natural
and renewable resource research and education,
funded by state, federal and local government,
and by gifts and grants from individuals, founda-
tions, government and industry.
" An organization whose mission is:
Educating students in the food, agricultural,
and related sciences and natural resources.
Strengthening Florida's diverse food and
agricultural industry and its environment
Enhancing for all Floridians, the application
of research and knowledge to improve the
quality of life statewide through IFAS exten-