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NC State Extension

2020 Zucchini Squash Cultivar Evaluations

Hort. Series # 237

Principle Investigators

Jonathan R. Schultheis, Professor and Extension Specialist
Keith D. Starke, Agricultural Research Associate
Maxton D. Collins, Research Assistant

General Cultural Practices

The squash study was established on white plastic mulch. Pesticides used on all plots were chemicals labeled for that crop, 2019 North Carolina Agricultural Chemicals Manual.

Acknowledgments

We gratefully acknowledge the assistance of Cathy Herring, (Superintendent), and Charles Barrow, (Horticulture Supervisor, Central Crops Research Station, Clayton, NC), as well as, the personnel at the research station for their help in establishing, maintaining, and harvesting the squash cultivar evaluation study. We want to acknowledge the following summer employees for their assistance with the study: Benjamin Indermaur, Tanner Seay, Daria Slack, as well as, graduate student; Alyssa Woodard. We would also like to thank Joy Smith for conducting the statistical analysis on the data that were collected in this study. The cooperation and support from Bejo, Enza Zaden, HM Clause, Rijk Zwaan, Sakata, Seedway, Seminis, Syngenta and VoloAgri are also appreciated. This research was also supported by a grant from USDA National Institute of Food and Agriculture Specialty Crop Research for the CucCAP Specialty Crop Research Initiative grant under award number 2015-51181-24285.

Disclaimer

This publication presents data from the cultivar evaluation study conducted during 2020. 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.

Table 1. Zucchini Squash Sources and Descriptions; 2020.

Cultigen

Seed Company

Description

Cardea Seedway Medium green fruit; mostly  straight with wider taper at blossom end; slight ridging entire length of fruit; average peduncle;  fruits not all perfect shapes,  with intermittent bulges throughout the length of the fruit; generally produced more marketable fruit across all harvests  compared with other entries.
Cash  Machine Enza Zaden Medium to dark green fruit; straight fruit with moderate taper at blossom end; slight ridging along entire fruit but not very discernable; average peduncle; very smooth fruit; most  compact plant of all entries.
Green Machine  Enza Zaden Medium green fruit; most fruit straight with no taper; ridging entire length of fruit; compact to average peduncle; fruit in 12th harvest were generally all too short; speckling more apparent than most other entries.
Leopard HM Clause Medium to dark green fruit; generally straight fruit but some  have slight curve; fruit taper at blossom  end; very slight ridging at stem end of fruit; average peduncle; pronounced speckling  give fruit slightly lighter green appearance;  intermittent  bulging along the length of fruit.
Respect HMClause Generally dark green fruit; mostly straight  fruit with taper at blossom end; ridging along length of fruit; compact to average peduncle;  fruits throughout entire trial did not size and appeared to lack adequate significant pollination; multiple fruit on plants remained small and these fruit all had dark green color.
Spineless  King Seedway Medium green fruit; straight fruit with slight taper at blossom end; slight ridging mainly on stem end; average peduncle; fruit were generally longer than desirable for markets; fairly pronounced speckling on fruit.
Spineless  Supreme  Syngenta Medium to dark green fruit; generally straight fruit with slight taper at blossom end; slight ridging primarily near stem end; compact to average peduncle; most fruit had bulging along the entire length, which diminished fruit quality.
 Tribute HM Clause Medium green fruit; generally straight fruit with taper at blossom end; slight ridging at stem end; average peduncle;  a few fruit with tendency to slightly bulb at blossom end; speckling noticable.
23-147 RijkZwann Medium to dark green fruit; generally straight fruit with slight taper at blossom end; very slight ridging entire length of fruit; average to long peduncle;  limited marketable fruit to make ratings because most were culls.
1023-401 Rijk Zwann Dark green fruit; generally straight with slight taper at blossom end; slight ridging primarily at stem end; average to long peduncle; many fruits had bulges or had bulbous blossom end resulting in more culls and lower fruit grades.
697 Seedway Mainly dark green fruit; generally straight fruit withtaper; slight ridging entire length of fruit; compact peduncle;  some fruit tend to have skinny neck at stemend.
A10129 Bejo Medium to dark green fruit; straight fruit with taper atblossom end; slight ridging the entire length of fruit;average peduncle; slight bulging along length of fruit.
A10131 Bejo Medium to dark green fruit; mainly straight with widertaper at blossom end; pronounced riding entire lengthof fruit; average peduncle;  fruit tend to be longer thanmost  other entries.
A10133 Bejo Medium to dark green fruit; straight fruit with slighttaper at blossom end; slight ridging at stem end offruit; average peduncle;  tendency to have  bend onsome  fruit at stem end.
A10138 Bejo Medium to dark green fruit; mainly straight fruit withslight taper at blossom end; slight ridging entire length of fruit; compact to average peduncle;  does have atendency  to produce long, skinny fruit that may not taper.
A10139 Bejo Dark green fruit; straight fruit with very slight taper at blossom end; minimal ridging entire length of fruit;compact to average peduncle;  slender/longer fruit notsuitable for markets.
A10141 Bejo Medium to dark green fruit; straight fruit with taper atblossom end; slight ridging at stem end of most fruit;average peduncle; several fruit had slight bend along middle of fruit.
Bejo Experimental 10 Bejo Medium green fruit; straight with wider taper atblossom end; slight ridging entire length of fruit;average peduncle; good legnth to width ratio.
E28Z.0069 Bejo Medium green fruit; generally straight fruit with wider taper at blossom end; slight ridging entire length offruit; compact to average peduncle;  tendency  for most fruit to have skinny or constricted neck at stem end.
HMC 2439 HM Clause Medium to dark green fruit; straight fruit with slight taper at blossom end; generally very slight ridging at stem end of fruit; compact to average peduncle; severe bulging along length of several fruit casuing them to be classified as grade 2 or culled.
SVYG 0914 Seminis Medium to dark green fruit; straight fruit with taper at blossom end; slight ridging at stem end; long peduncle size; neck on some fruit slightly skinnier than desirable; majority of fruit with good market fruit length width dimensions.
SVYG 9956 Seminis Medium to dark green fruit; straight fruit with taper at blossom end; very slight ridging mainly at stem end of fruit; long peduncle; fruit length width ratio good for markets.
USAS 17150 VoloAgri Medium green fruit; straight fruit with moderate taper at blossom end; slight ridging at stem end; compact to average peduncle; pronounced speckling; most consistent producer in study with respect to fruit shape.
XSQ 4508 Sakata Medium to dark green fruit; generally straight fruit with taper at blossom end; slight ridging entire length of fruit; compact to average peduncle; several fruit with noticable bulges resulting in less attractive appearance and demotion to grade 2 fruit.

Zucchini Squash Cultural Practices for 2020 Cultivar Study, Central Crops Research Station; Clayton, NC

Introduction

Summer squash production in North Carolina totaled 4,600 acres in 2019 according to the most recent agricultural data. This was an increase of 800 acres from 2018 when summer squash production was reported to be 3,800 acres. More impressive was the $20.3 million dollar crop value of the 2019 squash crop, which surpassed the previous years’ crop by more than $2 million dollars (View the data from the 2019 State of NC Agriculture Overview). Summer squash ranks among the top 10 vegetables grown in North Carolina with Cleveland County (south central North Carolina) producing the greatest acreage of squash in the state. Moreover, summer squash remains an important crop to North Carolina producers as the state is ranked 5th among those states that produced the crop nationwide in 2019 (View data from the USDA Economic Research Service). North Carolina growers have maintained their competitiveness through producing squash cultivars that are highly desired by the consumer. In an effort to remain competitive in the marketplace and maximize profitability most growers seek to grow squash cultivars that will provide them with the highest yields and greatest overall fruit quality. The zucchini market in North Carolina has typically been supplied with a fruit that is medium green in color; however, some markets have seen increased demand for cultivars that produce a darker green fruit. Summer squash plantings in North Carolina typically experience higher incidence of disease and insect pressure since they are harvested in the fall when environmental factors favor increased presence of these plant pests and pathogens. In 2020 the field study was planted on 2 June and we began harvesting on 8 July. The squash were rated for marketable and nonmarketable yields, for early and late production, and for consistency of production throughout the harvest period. Quality measurements were collected and average plant stand counts were determined to conduct the most complete evaluation of each cultivar in the field study. We again included the number of fruit produced per plant over various harvest intervals, and for the entire production season to compliment the yield data.

rows of squash plants in the field

2020 Zucchini Squash Cultivar Evaluations at the Central Crops Research
Station in Clayton, NC

Materials and Methods

Seeds were sown on 2 June 2020. Hills with seed skips were replanted 10 days after planting to maximize plant stand counts in each plot. Final stand counts were determined on 19 June (17 days after initial planting). The study area was treated with Telone C-17 (10 gal/ac) on 21 November 2019. A broadcast application of 12-6-24 pre-plant fertilizer (400 lb/ac) was made across the entire study area on 20 March 2020. White plastic mulch (1.25 mil thick high density film, 48 inches wide; B.B. Hobbs, Clinton, NC) and drip irrigation tape (NETAFIM, 12 inch spacing, 0.24 gal/min.; NETAFIM, Tel Aviv, Israel) was laid out in the field on 20 March 2020. The herbicides Gramoxone (3 qts/ac), Roundup (1 qt/ac) and Prefar (5 qts/ac) were applied as a on a rotational basis beginning 7 May and on the following dates: 3 and 30 June; 1 and 30 July 2020. The insecticides Assail and FanFare, were applied on a rotational basis as a preventative measure beginning 10 June and on the following dates: 18 and 25 June; 8, 16, 22, and 29 July; 6 August 2020. The following fungicide products were applied as a preventive measure and on a rotational basis throughout the entire growing season: Pristine, Procure, Ranman, and Vivando.

The first fungicide application was made on 18 June; and on the following dates: 25 June; 1, 8, 16, and 22 July 2020. Liquid fertilizer (4-0-8) was applied through drip irrigation beginning 24 June and on the following dates: 1, 8, 15, 22, 29 July; 3 and 12 August 2020. A total of 55.5 gallons of 4-0-8 liquid fertilizer was applied throughout the season. Harvests were conducted three times per week. The first harvest was 8 July and the final harvest (#12) was completed on 3 August 2020. The study was maintained with fertilizer applications until 12 August meanwhile fungicide treatments were discontinued on 6 August in order to facilitate powdery mildew to develop. Two ratings to assess susceptibility to powdery mildew were taken on 14 and 20 August 2020.

Most fruit were harvested when the blossom was detached from the fruit, and then categorized as marketable or non-marketable. Typically, marketable fruit would be graded into number one ‘fancy fruit’, while fruit that were slightly off in shape or color but still very marketable would be graded as number two fruit. Fruit that were small or apparently not pollenated, or were misshapen, were categorized as culls (non-marketable). Graded fruit were weighed and counted for each category and plot. The study design was a randomized complete block with four replications. In addition to yield, other quality measurements taken were: percent plant stand and average fruit length and width, plant architecture, fruit color, and spine ratings of the plant.

Results

Photographs of marketable fruit were taken on 15 and 31 July 2020; 7 and 14 August 2020 (Figure 1). Representative photos were also taken of zucchini fruit grades (Figure 2) and fruit shapes (Figure 3). A description of each zucchini cultivar is provided in (Table 1). This subjective information compliments the objective data presented in the remainder of the study (Tables 2- 12). The highest yielding (> 450 boxes/acre) cultigens (advanced line or cultivar) for marketable fruit in early harvests (1-4) were Cardea, Cash Machine, 23-401, Bejo Experimental
10, HMC 24939, SVYG9956, and XSQ4508 while the lowest yielding (< 250 boxes/acre) were Spineless Supreme, 23-147, and A10131 (Table 2). Mid-season included 4 harvests (5-8) (Table 2). On average yields were higher in the early-season versus the mid-season or late season harvests (9-12). The highest yielding mid-season cultigens (> 450 boxes/acre) for marketable fruit were Cash Machine, 23-401, HMC 24939, SVYG9956 and USAS 17150. Cultigens with the highest marketable yields (>350 boxes/acre) in the late season harvests (9-12) were Cardea,
23-401, HMC 24939, SVYG9956 and USAS 17150 (Table 2). The highest cull fruit production was in the late season harvests for all cultigens except A10139 and A10141 (Table 2). The cultigens that produced the most culls (>125 boxes/acre) were Cash Machine, Green Machine, Respect, Tribute, 23-147 and XSQ4508 (Table 2). No virus symptoms were observed in any fruit.

Marketable yields across all harvests (12) were greatest (> 1200 boxes/acre) for Cardea, Cash Machine, 23-401, HMC 24939, SVYG9956 and USAS 17150 while Respect, Spineless Supreme, 23-147, A10131 and A10141 had the lowest marketable yields (<800 boxes/acre) (Table 3). Fruit grade percentages across all harvests averaged 67% for number one fruit and 16% for number two fruit. The cultigens that produced the highest percentage of number one fruit (>75%) were Leopard, 23-401, 697, Bejo Experimental 10, E28Z.00697, SVYG9956 and USAS 17150. The cultigens with the lowest cull fruit production (<10%) were Leopard, 23-401, Bejo Experimental 10, SVYG9956 and USAS 17150. Disease pressure was minimal throughout

the season in this study. Marketable fruit averaged 83% across all entries for the season (Table 3). Entries above the marketable fruit average were Cardea, Leopard, Spineless King and 23- 401, 697, A10133, Bejo Experimental 10, E28Z.00697, HMC 24939, SVYG0914, SVYG9956, USAS 17150 and XSQ4508. The entries with the highest cumulative yield (12 harvests) of marketable fruit were SVYG9956 (1400 boxes/acre) followed by 23-401 (1362 boxes/acre), USAS 17150 (1354 boxes/acre), HMC 24939 (1322 boxes/acre) and Cash Machine (1317 boxes/acre).

The highest percentage of marketable squash, averaged across entries, was obtained in the early season harvests (1-4) (89%) followed by mid-season harvests (5-8) (86%) and late season harvests (9-12) (74 %) (Table 4). The percentage yield of marketable fruit was especially high for Leopard, HMC 24939 and SVYG9956 (97%) for early season harvests (1-4); 23-401 (99%) and USAS 17150 (97%) for mid-season harvests (5-8); and for late season harvests (9-12) USAS 17150 (95%). Fruit quality declined throughout the season with the highest percentage of number one fruit occurring in the early season harvests (76%) and the lowest percentage of number one fruit occurring in the late season harvests (52%). Similarly, the lowest percentage of number two fruit occurred in the early season harvests (13%) and increased throughout the remaining harvests.

The average number of fruit per plant for each entry during three harvest intervals are shown in Table 5. Cumulative marketable fruit weight per plant over all harvests (12) averaged 4.7 lbs (Table 6), while cumulative marketable fruit number per plant averaged 12 and comprised 70% of the fruit harvested (Table 7).

The cumulative number of fruits per acre for each cultigen across all harvests (12) and for each grade are provided in (Table 8). The number of fruits per acre for each cultigen for early season harvests (1-4), mid-season harvests (5-8) and late season harvests (9-12) are provided in Table 9, with corresponding percentages in Table 10.

Plant stands were excellent with no cultigens averaging less than 95%. Data for fruit length and width were collected from four separate harvests (Table 11). Length and width of five marketable fruit per plot were taken in order to obtain an average length/width ratio for marketable fruit. In this study, cultigens that produced the longest fruit were A10138, Tribute, and A10131. In addition, all plots in the study were rated for the following characteristics: plant architecture (open or closed stalk positioning/density), plant vigor, fruit color, presence or absence of spines and powdery mildew resistance (Table 12). Cultigens with a dense architecture included Cash Machine and Spineless King, while cultigens with more openness were XSQ4508 and A10131 (Table 12). Cultigens with few or no spines were Spineless King, Spineless Supreme, and USAS 17150. The most vigorous vine growth was recorded on Cardea, while the cultigen with the least vigorous vines was HMC 24939 (Table 12). The cultigens with the lowest average incidence of powdery mildew were A10131, Bejo Experimental 10, A10139 and A10141 (Table 12).

figures 2 and 3

Figure 2 (top) Zucchini Squash Fruit Grades: US #1 – fancy, US #2, and Cull
Figure 3 (bottom) Illustration of intermittent bulging exhibited in some zucchini squash fruit throughout all harvests.

Summary

Overall, yields and fruit quality in this study were below average. Fruit grades diminished throughout the study with number two fruit and culls increasing as the season progressed. This study was planted nearly five weeks later than usual due to the COVID-19 pandemic. Exceptionally high heat indexes throughout the growing season may have had a negative impact on the study. We observed predominantly male flowers on the squash plants throughout July, which may have negatively impacted plant fruit set potential and the shape of set fruit. This could explain the low yield that occurred in the study. We have observed much higher yields in past years when plantings were made earlier in the season insert linkS uash booklet on CuCap webpage for 2018 and 2019 . Despite the later plant date neither insect pests nor disease pressure was an issue throughout the season.

Table 2. Zucchini Squash cultigen study yields¹, number of 20 lb boxes per acre, per indicated harvests for replicated treatments. Clayton, NC, 2020.¹

Cultigen

Fruit Grade #1

Fruit Grade #2

Culls

Total

Harvests

Harvests

Harvests

Harvests

1 – 4

5-8

9-12

1 – 4

5 – 8

9 -12

1 -4

5 -8

9 -12

1 – 4

5 – 8

9 -12

Cardea 462 337 276 29 43 96 39 35 102 530 415 475
Cash  Machine 432 389 219 53 123 101 43 96 160 528 607 480
Green Machine 317 295 120 103 115 152 43 62 147 463 472 419
Leopard 362 269 248 60 66 67 13 26 42 435 361 358
Respect 257 94 90 52 54 65 24 74 206 333 222 360
Spineless  King 309 296 149 36 58 97 17 18 60 362 372 306
Spineless  Supreme 203 227 126 22 66 61 12 60 82 237 354 269
Tribute 273 262 221 63 86 94 89 82 126 426 430 441
23-147 172 160 42 41 108 73 64 91 178 278 359 292
1023-401 439 490 304 42 19 68 26 4 40 507 513 412
697 338 260 247 20 20 50 34 43 52 392 323 349
A10129 268 266 168 71 66 82 96 53 94 434 386 344
A10131 195 166 163 49 53 48 50 73 87 293 292 299
A10133 356 307 235 79 65 92 30 30 121 466 403 448
A10138 252 255 196 98 79 82 53 36 104 403 370 383
A10139 304 211 221 75 58 61 94 74 81 473 343 363
A10141 244 157 194 66 71 57 82 84 73 393 312 324
Bejo Exp. 10 441 312 228 59 25 109 36 12 31 535 348 368
E28Z.0069 352 262 261 11 29 45 26 30 53 389 322 359
HMC 2439 437 404 248 30 67 137 16 36 121 482 507 506
SVYG 0914 319 291 173 13 45 54 30 30 66 362 366 294
SVYG 9956 515 423 241 25 69 128 14 22 90 553 513 459
USAS 17150 377 434 433 22 31 58 19 13 26 418 478 516
XSQ 4508 399 241 164 80 66 82 31 32 126 510 339 372
Average 334 284 207 50 62 82 41 47 94 425 392 383
LSD (0.05) 314 250 190 62 77 74 74 86 88 296 237 192

Table 3. Zucchini Squash cultigen study yields, cumulative boxes, (20 lbs.), per acre, among all harvests1. Clayton, NC, 2020.

 Cultigen

Cumulative boxes per acre

Percent (%)

 Total

Fruit Grade#1

Fruit   Grade#2

 Culls

 Total

Fruit Grade#1

Fruit Grade#2

 Culls

Cardea 1075 168 176 1419 75 12 13 87
Cash Machine 1040 277 299 1616 64 17 19 81
Green Machine 732 369 252 1353 52 28 20 80
Leopard 880 193 81 1154 76 17 7 93
Respect 441 171 304 916 48 18 34 66
Spineless King 754 191 95 1040 72 18 10 90
Spineless Supreme 556 149 155 860 62 18 20 80
Tribute 757 243 297 1296 58 19 24 76
23-147 374 222 333 929 40 24 36 64
23-401 1233 129 70 1432 86 9 5 95
697 845 90 129 1064 79 8 12 88
A10129 702 219 242 1163 57 19 24 76
A10131 524 151 210 885 56 18 26 74
A10133 898 237 182 1317 68 18 14 86
A10138 702 259 194 1156 60 22 18 82
A10139 736 194 249 1179 62 17 22 78
A10141 595 195 239 1029 56 19 24 76
Bejo Exp. 10 980 192 79 1251 78 15 7 93
E28Z.00697 875 85 109 1069 81 8 11 89
HMC 24939 1089 234 173 1495 72 16 12 88
SVYG0914 783 112 126 1021 72 12 15 85
SVYG9956 1178 222 126 1526 77 14 8 92
USAS 17150 1244 111 57 1412 88 8 4 96
XSQ4508 804 227 190 1221 65 19 16 84
Average 825 193 182 1200 67 16 17 83
LSD (0.05) 604 133 179 563 27 23 23 23