This replicated experiment was conducted at LIHREC in 2020.
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Powdery mildew (PM) is the most important disease affecting cucurbit crops, occurring every year throughout Long Island as well as the rest of the U.S. Management is needed to avoid loss in yield and especially fruit quality. Flavor of melons and squashes is poor and they lack sweetness when leaves senesce prematurely due to a disease like PM not being successfully managed. Fungicides and PM resistant (PMR) varieties are the only management tools for PM. Using an integrated program with fungicides applied to PMR varieties is recommended to ensure good control and to minimize selection pressure on the pathogen to develop resistance. This pathogen has proven adept at developing resistance, especially to targeted fungicides. PMR cucurbit varieties are an important tool for managing this important disease for both organic and conventional growers. In past evaluations at LIHREC, PMR varieties have exhibited a range in level of suppression from poor to excellent. It is helpful for growers to know how well new varieties perform in terms of ability to suppress a disease, in order to select a fungicide program to achieve desired level of control, and also to know yield and fruit quality compared to standard varieties to determine whether a new variety is suitable for their operation. The goal of this project was to evaluate three new cantaloupe varieties: Halona, Shockwave and Sugar Rush. Two adjacent experiments were conducted, one was treated weekly with PM fungicides starting at first detection of symptoms to evaluate the PMR varieties as part of an integrated management program.
Procedures:
Experiments were conducted at the Long Island Horticultural Research and Extension Center (LIHREC) in Riverhead, NY, in a field with Haven loam soil. Controlled-release fertilizer (N-P-K, 19-10-9) at 525 lb/A (101 lb/A N) was broadcast over the bed area and incorporated on 22 Jun. Beds were formed with drip tape and covered with black plastic mulch also on 23 Jun. A waterwheel transplanter was used to make planting holes in the beds and apply starter fertilizer. Cantaloupe was sown in trays in a greenhouse on 1 Jun, then seedlings were transplanted by hand into the holes on 24 Jun. Plants that died were replaced on 29 Jun, 7 Jul and 13 Jul. To separate plots and provide a source of inoculum, there were two powdery mildew-susceptible summer squash plants (cv. Slick Pik) between plots.
Plots were three 10-ft rows spaced 68 in. apart with 12 plants per plot at 2-ft spacing. There were two adjacent experiments. In one experiment, PM was not managed while in the second experiment, it was treated with fungicides using a tractor-drawn boom sprayer (50 GPA and 125 PSI) to evaluate the PMR varieties as part of an integrated management program: Procure and Vivando applied in rotation weekly. A randomized complete block design with four replications was used.
PM severity on upper and lower leaf surfaces of cantaloupe was rated in each plot on 22 and 29 Jul; 3, 10-11, 17-18 and 24-25 Aug; and 1 and 8 Sep. Area Under Disease Progress Curve (AUDPC) values were calculated from 18 Aug through 1 Sep to obtain a summation measurement of PM severity for the entire assessment period. Fruit were harvested when mature on 11, 18, 21, and 26 Aug. Last ripe fruit were counted on 1 Sep. A refractometer was used to measure sugar content (Brix) of juice from a fruit from each plot. Fruit quality evaluations were conducted with CCE and LIHREC staff. There were 10 raters for most varieties; only 2 for Astound and Shockwave. All data except ratings were statistically analyzed.
To examine the reported longer shelf-life of Shockwave, two ripe and two near-ripe fruit of this variety and of Ambrosia were harvested on 25 Aug. One set of four fruit were kept at ambient temperature in a barn; the other four fruit were kept in a refrigerator. Fruit in the barn were examined on 28 Aug and 2 Sep. Fruit in the refrigerator were examined on 31 Aug, and 4, 10, and 14 Sep.
Results:
Powdery mildew was first observed on 17-18 Aug in 4 of the 48 plots at low levels. Severity remained very low through 1 Sep, even in non-fungicide-treated plots, in contrast with an adjacent experiment with powdery mildew resistant acorn varieties. Average severity on upper and lower leaf surfaces of non-fungicide-treated Ambrosia, the variety with numerically the most symptoms, was 1.6% and 0.7%, respectively, on 1 Sep, which was the end of the harvest period, then increased to 13.1% and 19.5% on 8 Sep. Low severity is reflected in the exceptionally small AUDPC values (Table 1).
Sugar Cube produced the smallest fruit as expected for this variety. Fruit weight was greatest for Ambrosia. Sugar Rush and Halona produced significantly more fruit early in the harvest period (11 – 18 Aug). Shockwave produced fruit with highest sugar content; Ambrosia and Astound had significantly lower Brix values (Table 1).
Fruit of Sugar Cube, Sugar Rush, and Shockwave received the highest average ratings for taste (Table 2). Astound and Sugar Rush had best texture. External appearance was rated higher for Halona, Sugar Cube, and Sugar Rush than the others. Shockwave received highest rating for internal appearance. Sugar Cube had best shape. Astound and Halona had best size. Astound, Shockwave, and Sugar Rush were described as having good firm texture (Tables 3 and 4).
Most Shockwave fruit in the shelf-life assessment lasted longer than the Ambrosia fruit. Of the fruit stored in a barn, only the ripe Shockwave fruit remained firm for at least 3 days, but less than 8 days. Of the fruit stored in a refrigerator, both Ambrosia fruit were beginning to soften after 6 days and had surface mold after 10 days, while the ripe Shockwave fruit was still firm after 16 days. It had soft spots 20 days after harvest.
Lists and tables of resistant vegetable varieties that include seed companies marketing them and whether organic seed is available, as well as variety resistance to disorders, are available at the Cornell Vegetables website. Also at that site: Information about powdery mildew and its management.
Acknowledgments: This project was supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, Hatch under NYC-153409 and the Friends of Long Island Horticulture Grant Program.
Margaret Tuttle McGrath
Plant Pathology and Plant-Microbe Biology Section, SIPS, Cornell University
Long Island Horticultural Research and Extension Center
3059 Sound Avenue, Riverhead, NY 11901
mtm3@cornell.edu
Tables
Table 1. Severity of powdery mildew on resistant varieties of cantaloupe that were not treated with fungicides for this disease, followed by yield data from fungicide-treated plants.
| Powdery mildew severity (AUDPC)* | Yield* | |||||
| Variety (reaction to powdery mildew) | Upper leaf surface | Lower leaf surface | Fruit Wt (lb) | Brix | No. fruit/plant* | |
| Early | Total | |||||
| Ambrosia (resistant) | 5.94 | 2 ab | 7.60 a | 10.2 c | 0.04 b | 3.19 |
| Astound (resistant) | 2.77 | 2 ab | 4.66 c | 11.4 bc | 0.00 b | 3.67 |
| Halona (resistant) | 0.00 | 0 b | 6.15 b | 12.0 abc | 0.98 a | 3.19 |
| Shockwave (resistant) | 10.46 | 7 a | 4.98 c | 15.0 a | 0.00 b | 3.81 |
| Sugar Cube (resistant) | 0.01 | 0 b | 2.64 d | 13.6 ab | 0.38 b | 3.21 |
| Sugar Rush (resistant) | 3.87 | 1 b | 4.73 c | 13.2 abc | 1.02 a | 3.46 |
| P-value (variety) | 0.0893 | 0.0008 | <0.0001 | 0.0032 | <0.0001 | 0.5941 |
| *Numbers in each column with a letter in common are not significantly different from each other (Tukey’s HSD, P=0.05). | ||||||
Table 2. Fruit of resistant varieties of cantaloupe were evaluated on a 1 (poor) to 5 (excellent) scale for several parameters by CCE and LIHREC staff. Values are average rating, overall average, and percentage of raters who indicated they would buy the variety.
| Appearance | Would you buy? | |||||||
| Variety | Size | Shape | External | Internal | Taste | Texture | Average | |
| Ambrosia | 3.6 | 3.9 | 3.4 | 3.3 | 3.3 | 2.9 | 3.4 | 50% |
| Astound | 4.5 | 4.3 | 3.9 | 3.8 | 3.4 | 4.3 | 4.0 | 100% |
| Halona | 4.4 | 4.1 | 4.1 | 3.8 | 3.5 | 3.7 | 3.9 | 93% |
| Shockwave | 4.2 | 4.0 | 3.5 | 5.0 | 3.7 | 3.5 | 4.0 | 50% |
| Sugar Cube | 3.8 | 4.8 | 4.2 | 4.1 | 4.0 | 3.7 | 4.1 | 70% |
| Sugar Rush | 4.2 | 4.4 | 4.0 | 4.0 | 3.7 | 4.2 | 4.1 | 65% |
Table 3. Comments about fruit from evaluators, followed by number of raters who made the same comment if more than one (in parenthesis).
| Variety | Comments |
| Ambrosia | green-beige external rind (2), flesh color a little more orange and internal rind better green color than Halona, mealy perhaps due to fruit being over ripe, not uniform in size |
| Astound | nice firm flesh, not mealy or soft even with a fruit held many days until looked overripe on outside, flavor really good through to edge of rind |
| Halona | external appearance good-classic sutures, flesh color light orange, internal rind pale green |
| Shockwave | flesh deeper orange and internal rind edge deeper green than others, flesh nice and firm, not very juicy |
| Sugar Cube | flavor really good even with over-mature fruit, flesh and internal rind color good, external appearance very good; very small, weird taste |
| Sugar Rush | good firm flesh, flavor varied a bit among bites |
Table 4. Comments and ratings about fruit from Sandy Menasha, CCE Vegetable/Potato Specialist. Ratings are on a scale of 1 (poor) to 5 (excellent).
| Appearance | ||||||||
| Variety | Size | Shape | External | Internal | Taste | Texture | Would Grow | Comments |
| Ambrosia (susceptible) | small-large | oval | uneven color and shape and size; green, slight ridges | light-medium orange; light green rind; small cavity | No flavor; No melon; no sweetness: 2.7 | soft, juicy, meaty: 2.7 | no | green colored, uneven size and shape, ok netting, no ridges, ok to good netting |
| Astound | large | oval | good net, good color and shape; uniform | light orange-dark orange; good rind; nice, large cavity | good melon; good sweetness: 3.9 | soft but slightly firm, nice texture: 4.4 | yes | uniform slight ridges, large, good netting |
| Halona | medium, mostly large | round to slight oval | deep sutures, cracks, good netting | light green rim; light orange; deep cavity holes | good melon; good sweetness: 4.4 | soft but some bites good | yes | appearance: 3.9 rating, deep ridges, cracks around stem end, large, lots of cracks on fruit |
| Sugar Rush | medium-medium large | round to slight oval | good netting, no ridges | bright green rim; light orange; medium cavity; small holes | good ok melon; ok sweetness: 3.9 | firm-slightly soft, like texture | no | do not slip, pointed stem end, appearance: 3.9, too many external defects and taste ok |
| Sugar Cube | small-medium small | round | very good netting, slight ridges | good bright orange; small cavity; nice green rim | sweet, slight watery, good melon: 4.4 | soft, melts in mouth: 3.9 | yes | personal size, good size and shape, overall appearance: 5 |
| Shockwave | medium | round to oval | green uniform, good- excellent net; very slight ridges; good shape | good orange; nice green rind; small cavity | no sweetness, no melon, cucumber taste: 2.2 | firm: 3.3 | no | green undertone, excellent netting, no ridges, very slight ridges |
Below: ripe fruit harvested from each variety.
