Horticulture Series #221

View or print a PDF version of this report.

Principle Investigators: Jonathan R. Schultheis, Professor and Vegetable Extension Specialist & Keith D. Starke, Research Associate, Department of Horticultural Science, NC State University, Raleigh, NC 27695-7609. Disclaimer: This publication presents data from the standard size and mini watermelon cultivar evaluation trials conducted during 2017. Information in this report is believed to be reliable but should not be relied upon as a sole source of information. Limited accompanying detail is included but excludes some pertinent information, which may aid interpretation.

General Cultural Practices

The watermelon trials were grown on black plastic mulch and fertigated with drip tube. Pesticides used on all plots were chemicals labeled for that crop, (2017 North Carolina Agricultural Chemicals Manual.

Acknowledgments

We gratefully acknowledge the assistance of Rodney Mozingo (Superintendent) and Wesley Hairre (Horticulture Supervisor), Horticultural Crops Research Station, Clinton, NC, as well as, the personnel at the research station for their help in establishing, maintaining, and harvesting the cultivar evaluation trials. We want to acknowledge the following summer employees for their assistance with the trials: Stephen Bajorek, Shannon Dexter, Elizabeth Indermaur, Katherine Phillips, as well as, graduate students; Fernando Montero De Espinosa and Marlee Trandel. The cooperation and support of Bayer Crop Science; DP Seeds; Hazera; HM Clause; K&B Seed Company; Origene Seeds; Sakata Seed Company; Seedway; Seigers; Seminis; and Syngenta Seeds, Inc. were also appreciated.

Introduction

Growing conditions for the 2017 watermelon crop were generally very favorable throughout the season. North Carolina has shown a modest increase in watermelon production from 2012 to 2015 where the average harvested acreage was (5,733 acres) and in 2016 harvested acreage was reported at 6,300 acres. North Carolina ranks #7 among watermelon producing states and represents 6% of the U.S. acreage which totaled 113,000 acres in 2016. This translates into $34.772 million in economic value to North Carolina, an increase from $32.364 million in 2015.

On average, watermelon fruit were slightly larger in the 2017 crop leading to greater supply of 30 and 36 count size categories and lesser availability of smaller (60 count) watermelon throughout the season (P. Westerbeek, personal communication). Recent reports indicate that standard size watermelon (wholes) still account for 80% of the US market followed by mini watermelon (10%) and cut watermelon (10%).

Mixed picture for North American watermelon supply in 2017

Materials and Methods

Once all seed were received from participating companies, they were planted into 72 cell Poly trays to grow transplants (Hummert Int.; Earth City, MO). Seeds of standard size cultigens were sown on 18 April 2017. The planting medium used was “Fine Germinating Mix”, a commercial soilless mix (SunGro, Agawam, MA). Approximately 3 weeks after seeding, transplants were placed in a “hardening” greenhouse for about one week before being established in the field. Standard size triploids were established in the field on 15 May 2017. Round-Up herbicide (1qt/ac) was applied to the entire area on 27 January 2017. The field was disced on 21 March 2017 and preplant fertilizer was applied on 27 March 2017 using the following fertilizer sources and rates (Broadcast Equivalent): 0-0-22 (200 lbs/acre), 6-3-18 (500 lbs/acre), 15.5-0-0 (200 lbs/acre), 0-0-50 (300 lbs/acre) and 0-46-0 (200 lbs/acre). On 10 April 2017, the field was fumigated with Pic-Clor60 at a rate of 260 lbs/acre (Broadcast Equivalent). Black polyethylene plastic (1.25 mil thick high density plastic film, 60 inches wide; B.B. Hobbs, Clinton, NC) was laid on 9 April 2017. Plot size for standard triploid size watermelons was 1 row, 10 plants per plot, 25 feet long with 10 foot alleys between plots. In most cases, plots with missing plants were replanted approximately 7 days after planting to achieve 100 % plant stand. ‘Ace Plus’ (2 plants/plot) and ‘SP-6’ (2 plants/plot) were used as diploid pollinizer (4 total plants/plot) in the 2017 growing season. Row middles were 10 feet for all watermelon types and in-row spacing was 2.50 feet for the standard size triploid watermelons. Drip tape (NETAFIM, 12 inch spacing, 0.24 gph; NETAFIM, Tel Aviv, Israel) was installed underneath the plastic mulch and was utilized to fertigate the crop throughout the growing season. The following herbicides were applied to row middles on 9 May 2017; Gramoxone (1qt/ac), Strategy (5pt/ac), Sandea (1oz/ac), Sinbar (4oz/ac). A subsequent application of Gramoxone (1qt/ac) was spot sprayed on weed escapes.

Irrigation was initially applied through drip tape on 9 May 2017 and similarly on the following dates; 11, 12, 15, 16, 17, 18, 19, 22 and 29 May 2017; 2, 12, 14, 28 and 30 June 2017; 3, 11, 14, 18, 21, 26, 28 and 31 July 2017; 3, 4 and 21 August 2017. Insecticides Asana (8oz/ac), Diazinon (1qt/ac), Sevin (1pt/ac), and Radiant (8oz/ac) were rotated and applied as a preventive measure on the following dates; 18 May 2017; 2, 16, 29 June 2017; 6, 21, 27 July 2017; 3, 15 August 2017. Insecticide products were rotated to avoid potential development of insect resistance. Liquid fertilizer with 7-0-7 analysis was initially applied through drip tape on 25 May 2017 and similarly on the following dates; 31 May 2017; 5, 7, 9, 13, 15, 19, 22, 26, 27, and 29 June 2017; 5, 7, 10, 12, and 19 July 2017; 2 and 10 August 2017. A total of 79 lbs/ac N and 79 lbs/ac K were applied via fertigation throughout the growing season. Cumulative totals of applied fertilizer for the growing season were: 112 N lbs/ac, 58 P lbs/ac, 234 K lbs/ac, respectively. Soil tests indicated that soil phosphorus levels were low therefore, 0-46-0 fertilizer was applied preplant. No additional phosphorus was applied during the season. Fungicides were initially applied on 2 June 2017 and similarly on the following dates: 16 and 29 June 2017; 6, 21, 27 July; 3 and 15 August. The following fungicides were rotated to avoid potential development of resistance from diseases; Bravo (1qt/ac), Cabrio (10oz/ac), Copper (1lb/ac), Inspire (16oz/ac), Manzate (3lb/ac), Presidio (4oz/ac), Previcur Flex (1.2pt/ac), Quadris (6oz/ac), Revus (8oz/ac), and Tanos (8oz/ac). Disease pressure was minimal throughout the season and overall plant health supported good crop yields. Each fruit was harvested when ripe, weighed and categorized statistically by size category. Standard size triploid watermelon harvests (5) took place on: 18 and 25 July 2017; 1, 8 and 22 August 2017. For the triploid standard size watermelon test, fruits were placed in the following categories: ≤ 9.0 lbs, 9.1 – 13.5 lbs, 13.6 – 17.5 lbs, 17.6 – 21.4 lbs, and ≥ 21.5 lbs. Fruits were considered marketable if they weighed 9.1 lbs or more. Fruit are often commercially marketed by number or count per bin with 9.1-13.5 lbs fruit termed 60-count, 13.6 – 17.5 lbs fruit termed 45 count, 17.6 – 21.4 lbs fruit termed 36-count, and fruit 21.5 lbs or larger termed 30-count. We used these weight designations to categorize the harvested fruits in this study. The most popular standard triploid fruit size has typically ranged from 12-16 lbs. Mini triploid watermelon were established in the field on 11 May 2017. Plot size for mini triploid size watermelons was 1 row, 8 plants per plot, 15 feet long with 8-foot alleys between plots. ‘Ace Plus’ (2 plants/plot) and ‘SP-6’ (2 plants/plot) were used as diploid pollinizer (4 total plants/plot) in the 2017 growing season. Row middles were 10 feet for all watermelon types and in-row spacing was 1.88 feet for the mini size triploid watermelons. Mini triploid watermelon harvests (6) occurred on: 11, 19 and 26 July 2017; 1, 8 and 22 August 2017. For the mini triploid watermelon test, fruits were placed in the following categories: ≤ 3.0 lbs, 3.1 – 7.0 lbs, 7.1 – 9.0 lbs, and ≥ 9.1 lbs. Evaluations of each watermelon entry included yield, fruit size, production earliness, soluble solids, using a handheld digital refractometer, fruit shape and size, exterior and interior descriptions (rind pattern, length/width ration, seed trace size, occurrence of hard seeds, hollow heart incidence and severity, and flesh color), and interior flesh firmness. Hard seed in triploid fruit was determined according to the USDA standards. Fruits were cut longitudinally in half, and then these halves were cut laterally. The number of hard seeds exposed on the cut surface were counted and recorded.

This is the fifth year we have rated for hard seeds according to the USDA standards. Flesh firmness was taken by using a Penetrometer FT 011 with a 7/16” plunger tip, (QA Supplies LLC, Norfolk, Va.), and recorded in pounds. Samples were obtained by cutting the center of the fruit from the stem to blossom end. Pressure was then taken in five areas of the fruit; stem end, top side, ground spot side, blossom end, and center. Pressure was not taken on fruit with hollow heart. The reported measures on flesh firmness are an average of the five sample areas and are an average value taken for five fruit per plot or 20 fruit per cultigen. Most of the quality measurements were taken at the first or second harvests.

Financial Support

In addition to seed companies, this research was supported by the College of Life and Agricultural Sciences, North Carolina Agriculture Research, and the North Carolina Cooperative Extension Services.

Table 1. Triploid Red-Flesh Watermelon Seed Sources and Descriptions; 2017.

Figure 1. View Standard Triploid Watermelon photographs in the PDF version of this report.

Table 2. Triploid Red-Flesh watermelon hybrid cultivar trial. Fruit weight, (cwt.), per acre by various weight classes including average fruit size¹ for harvest 1 and 2. Clinton, NC 2017

Cwt. (x100) by size

¹Yields are calculated using 100 percent seedless watermelon population. Ace Plus and SP-6 pollenizers were interplanted after triploid plants 1, 5, 7 and 10, (4 pollenizer plants/plot). Fruit weights for each category are rounded to the nearest whole number.
²Includes fruit ≥ 9.1 pounds.

Table 3. Triploid Red-Flesh watermelon hybrid cultivar trial. Bin boxes per acre by various weight classes including average fruit size¹ for harvest 1-2. Clinton, NC 2017.

Bin boxes / acre by size grade²    % Total Yield by count (TYC) ⁴

¹Yields are calculated using 100 percent seedless watermelon population. Ace Plus and SP-6 pollenizers were interplanted after triploid plants 1, 5, 7 and 10, (4 pollenizer plants/plot). Fruit weights for each category are rounded to the nearest whole number.
²Values were determined based upon 700 lb bin box weight.
³Includes fruit ≥ 9.1 pounds.
⁴Culls (≤ 9.0 lbs) are included in calculation for total yield by count for each respective bin category therefore total will not equal 100 percent.

Table 4. Triploid Red-Flesh watermelon hybrid cultivar trial. Fruit number for harvest 1-2 by various weight classes (per acre) including fruit number per plant. Clinton, NC 2017.

¹ Ranked according to total marketable number.
² Includes fruit ≥ 9.1 pounds.

Table 5. Triploid Red-Flesh watermelon hybrid cultivar trial. Fruit weight, (cwt.), per acre by various weight classes including average fruit size¹ for harvest 3-4. Clinton, NC, 2017.

Cwt. (x100) by size

¹ Yields are calculated using 100 percent seedless watermelon population. Ace Plus and SP-6 pollenizers were interplanted after triploid plants 1, 5, 7 and 10,
(4 pollenizer plants/plot). Fruit weights for each category are rounded to the nearest whole number.
² Ranked according to total marketable weight.
³ Includes fruit ≥ 9.1 pounds.

Table 6. Triploid Red-Flesh watermelon hybrid cultivar trial. Bin boxes per acre by various weight classes including average fruit size¹ for harvest 3-4. Clinton, NC, 2017.

Bin boxes / acre by size grade²   % Total Yield by Count (TYC)⁴

¹ Yields are calculated using 100 percent seedless watermelon population. Ace Plus and SP-6 pollenizers were interplanted after triploid plants 1, 5, 7 and 10, (4 pollenizer plants/plot). Fruit weights for each category are rounded to the nearest whole number.
² Values were determined based upon 700 lb bin box weight.
³ Includes fruit ≥ 9.1 pounds.
⁴ Culls (≤ 9.0 lbs) are included in calculation for total yield by count for each respective bin category therefore total will not equal 100 percent.

Table 7. Triploid Red-Flesh watermelon hybrid cultivar trial. Fruit number for harvest 3-4 by various weight classes (per acre) including fruit number per plant. Clinton, NC, 2017.

Fruit size category

¹ Ranked according to total marketable number.
² Includes fruit ≥ 9.1 pounds.

Table 8. Triploid Red-Flesh watermelon hybrid cultivar trial. Fruit weight, (cwt.), per acre by various weight classes including average fruit size¹ for harvest 5. Clinton, NC, 2017.

Cwt. (x100) by size

¹Yields are calculated using 100 percent seedless watermelon population. Ace Plus and SP-6 pollenizers were interplanted after triploid plants 1, 5, 7 and 10, (4 pollenizer plants/plot). Fruit weights for each category are rounded to the nearest whole number.
²Includes fruit ≥ 9.1 pounds.

Table 9. Triploid Red-Flesh watermelon hybrid cultivar trial. Bin boxes per acre by various weight classes including average fruit size¹ for harvest 5. Clinton, NC, 2017.

¹Yields are calculated using 100 percent seedless watermelon population. Ace Plus and SP-6 pollenizers were interplanted after triploid plants 1, 5, 7 and 10, (4 pollenizer plants/plot). Fruit weights for each category are rounded to the nearest whole number.
²Values were determined based upon 700 lb bin box weight.
³Includes fruit ≥ 9.1 pounds.
⁴Culls (≤ 9.0 lbs) are included in calculation for total yield by count for each respective bin category therefore total will not equal 100 percent.

Table 10. Triploid Red-Flesh watermelon hybrid cultivar trial. Fruit number for harvest 5 by various weight classes (per acre) including fruit number per plant. Clinton, NC, 2017.

¹Ranked according to total marketable number.
²Includes fruit ≥ 9.1 pounds.

Table11.Triploid RedFlesh watermelon hybrid cultivartrial. Cumulative weight, (cwt.), per acre of fruit harvested by various weight classes including average fruit size¹. Clinton, NC, 2017.

Cwt. (x100) by size

¹Yields are calculated using 100 percent seedless watermelon population. Ace Plus and SP-6 pollenizers were interplanted after triploid plants 1, 5, 7 and 10, (4 pollenizer plants/plot). Fruit weights for each category are rounded to the nearest whole number.
³Includes fruit ≥ 9.1 pounds

Table 12. 1 Triploid Red-Flesh watermelon hybrid cultivar trial. Bin boxes per acre by various weight classes including average fruit size¹. Clinton, NC, 2017.

Bin Boxes / Acre

¹Yields are calculated using 100 percent seedless watermelon population. Ace Plus and SP-6 pollenizers were interplanted after triploid plants 1, 5, 7 and 10, (4 pollenizer plants/plot). Fruit weights for each category are rounded to the nearest whole number.
²Ranked according to total marketable weight.
³Includes fruit ≥ 9.1 pounds.

Table 12. 2 Triploid Red-Flesh watermelon hybrid cultivar trial. Bin boxes per acre by various weight classes including average fruit size¹. Clinton, NC, 2017.

% Total Yield by Count⁴

⁴Culls (≤ 9.0 lbs) are included in calculation for total yield by count for each respective bin category therefore total will not equal 100 percent.

Table 13. Triploid Red-Flesh watermelon hybrid cultivar trial. Fruit number for cumulative harvests, (5), by various weight classes (per acre) including fruit number per plant. Clinton, NC, 2017.

Fruit size category

¹Ranked according to total marketable number.
²Includes fruit ≥ 9.1 pounds.

Table 14.1 Triploid Red-Flesh watermelon hybrid cultivar trial. Interior fruit quality. Clinton, NC, 2017.¹

¹Most measurements were obtained from fruits in harvest 1 and 2.
²SS = Indicates sweetness, average of 5 melons per replication (20 total).
³Rating: 1 = yellow, 2 = pink, 3 = red, 4 = medium-dark red, 5 = blood red.
⁴Rating: 1=small (i.e. tomato), 3=medium, 5=large.
⁵Average number of hard seeds couted within 5 melons per replication (20 total).
⁶LD = Length and diameter ratio, average of 5 melons per replication (20 total).
⁷Rind = Rind thickness (mm), measured from rind to where white and colored flesh meet.
⁸Fruit pressure was taken by a penetrometer, Fruit Pressure Tester – FT011

Table 14.2 Triploid Red-Flesh watermelon hybrid cultivar trial. Interior fruit quality. Clinton, NC, 2017¹.

Hollow Heart Ratings⁹

¹Most measurements were obtained from fruits in harvest 1 and 2.
⁹HH Percentage Rating Scale:
HH0: No crack in flesh
HH1: Slight crack in flesh
HH2: Small crack in flesh
HH3: Med. separation in flesh to rind.
HH4: Complete separation in flesh
**HH3 & HH4 = Non-marketable from QA Supplies LLC, Norfolk Va.

Table 15. Triploid-Mini Watermelon Seed Sources and Descriptions; 2017.

Figure 2. View Triploid Mini Watermelon photographs in the PDF version of this report.

Table 16. Triploid-Mini watermelon hybrid cultivar trial. Fruit weight, (cwt.), per acre by various weight classes including average fruit size¹ for early season harvests 1-2. Clinton, NC 2017.

Cwt. (x100) by size

¹Yields are calculated using 100 percent seedless watermelon population. Ace Plus and SP-7 pollinizers were interplanted after triploid plants 1, 3, 5 and 7 (2 Ace Plus and 2 SP-6 = pollenizer 4 plants/plot). Fruit weights for each category are rounded to the nearest whole number.

Table 17. Triploid-Mini watermelon hybrid cultivar trial. Fruit weight, (cwt.), per acre by various weight classes including average fruit size¹ for mid-season, harvests 3-4. Clinton, NC 2017.

Cwt. (x100) by size

¹Yields are calculated using 100 percent seedless watermelon population. Ace Plus and SP-7 pollinizers were interplanted after triploid plants 1, 3, 5 and 7 (2 Ace Plus and 2 SP-6 = pollenizer 4 plants/plot). Fruit weights for each category are rounded to the nearest whole number.
²Average of fruit ≥ 3.1 pounds.
³Includes fruit ≥ 3.1 pounds.

Table 18. Triploid-Mini watermelon hybrid cultivar trial. Fruit weight, (cwt.), per acre by various weight classes including average fruit size¹ for late season, harvests 5-6. Clinton, NC 2017.

¹Yields are calculated using 100 percent seedless watermelon population. Ace Plus and SP-7 pollinizers were interplanted after triploid plants 1, 3, 5 and 7 (2 Ace Plus and 2 SP-6 = 4 pollenizer plants/plot). Fruit weights for each category are rounded to the nearest whole number.

Table 19. Triploid-Mini watermelon hybrid cultivar trial. Fruit number for early¹ season harvests 1-2.Clinton, NC, 2017.

Fruit size category