Watermelon Research Report 2011 On-Farm Watermelon Survey

Transcription

1 Watermelon Research Report 2011 On-Farm Watermelon Survey Gordon Johnson Extension Fruit and Vegetable Specialist University of Delaware Elbert N. & Ann B. Carvel Research and Education Center County Seat Highway Georgetown, DE Phone: (302) Fax: (302)

2 On-Farm Watermelon Survey An on-farm watermelon survey was conducted in watermelon grower fields in 2011 to gather information that might direct future research. Emphasis was on gathering data on early fruit set and seedless and pollenizer health and vigor. Materials and Methods Fourteen watermelon fields with 21 plantings representing 12 cooperating growers were surveyed from the third week in May through the last week in June. Weekly visits were made and data was collected on male flower counts, fruit set, fruit set location, stem number and length, vigor ratings, and health ratings for seedless plants and nearby pollenizers. In addition, plant temperatures were recorded using an infrared thermometer on leaves and plant crowns. At all sites, 5 locations in each field were randomly selected for sampling each date and planting and a seedless plant and neighboring pollenizer plant were chosen to collect data from. To assess crown set and later fruit set, the node where the first fruit being carried was recorded. Total fruit being carried was also counted. In weeks 2-4, total male flowers were counted in pollenizer plants; whereas from week 5 on, one representative stem was used for flower counts. Counts included flowers that were open on the day of sampling and flowers open the previous day (browned). Initially, nodes that had male flowers previously were also estimated. Main branches were counted on seedless and pollenizer plants each visit and side branches were counted on one representative stem from pollenizer plants from week 5 on. The length of one representative stem was also recorded for both seedless plants and pollenizers. Vigor and health ratings were assigned to both seedless and pollenizer plants on a scale of 1 being lowest or worst and 10 being highest or best respectively. Plant temperatures of both seedless and pollenizer plants were recorded using an infrared thermometer. Crown temperature was recorded by aiming at the center of the plant crown on the bed and leaf temperature was recorded from the center of a recent fully expaned leaf. Results and Discussion Mean first node set for seedless fruit are presented in Tables 1 and 2 by seedless variety and pollenizer used respectively. First node set was significantly closer in Troubadour (6.84) than in Liberty, Melody, or Sugar Heart (9.35, 9.57, and 9.10 respectively) indicating earlier crown set in Troubadour. 7167, 7187, Crunchy Red, and Fascination were intermediate. Mean first node set for seedless fruit by seedless variety or pollenizer used and vigor rating are presented in Tables 3 and 4. In general, as seedless plant vigor increased, crown set was earlier (11.0 at vigor rating of 4 to 6.4 at vigor rating of 10). In the seedless varieties, crown set was least affected over a range of vigor ratings in 7187

3 and Fascination; whereas Crunchy Red had delayed crown sets below a vigor rating of 7 and Melody had delayed crown sets when vigor decreased below a vigor rating of 8. First seedless node set by pollenizer used was variable and did not show similar trends with the exception of Pollimax where early set was improved with higher vigor ratings. Table 1. Mean first fruit node for seedless fruit set by seedless variety. Seedless Variety Mean First Node Set ab ab Cr. Red 7.99 ab Fascination 7.92 ab Liberty 9.35 b Melody 9.57 b Sugar Heart 9.10 b Troubadour 6.84 a *Mean separation by pairwise t-tests.05 level. Table 2. Mean first node set for seedless fruit set by pollenizer. Pollenizer Mean First Node Set Accomplice 6.98 a Micky Lee 8.50 ab Pata Negra 5.25 a Pollimax 7.59 ab SF b SP ab Sidekick 7.74 ab Stargazer 7.76 ab Tropical 8.25 ab *Mean separation by pairwise t-tests.05 level.

4 Table 3. Mean first node set for seedless fruit by seedless variety and vigor rating. Variety Vigor Rating Mean first node set Crunchy Red Fascination Melody Sugar Heart Troubadour Overall Table 4. Mean first node set for seedless fruit by pollenizer and vigor rating. Vigor Rating Pollenizer Mean first node set Accomplice Micky Lee Pata Negra Pollimax SF SP Sidekick Stargazer Tropical Overall

5 Mean first node set by seedless leaf temperature is shown in Figure 1. Crown set was earlier when leaf temperatures were below 75 F. First node set by pollenizer leaf temperature is presented in Figure 2. Crown set was earlier when pollenizer leaf temperatures were below 70 F. This suggests that in plants with higher temperatures, the higher plant metabolism limits resources for early fruit set.

6 Mean number of fruit carried by seedless variety and pollenizer used are shown in tables 5 and 6. Fruit number in seedless varieties was measured from weeks 5-8 (from full set to first harvest). Liberty carried significantly fewer fruit that the rest of the varieties surveyed during this period and Melody and Crunchy Red had signficantly fewer fruit than Sugar Heart. There were significantly fewer fruit when Pollimax or SF800 were used as pollenizers when compared to Accomplice, Micky Lee, or Pata Negra. Table 5. Mean number of fruit carried weeks 5-8 by seedless variety. Seedless Fruit No. Sugar Heart 3.12 a* Fascination 2.87 ab Troubadour 2.75 abc abc abc Crunchy Red 1.89 bc Melody 1.81 bc Liberty 1.66 c *Mean separation by pairwise t-tests.05 level. Table 6. Mean number of seedless fruit carried by pollenizer. Pollenizer Fruit No. Accomplice 2.69 a* Micky Lee 3.00 a Pata Negra 2.89 a Pollimax 1.59 b SF b SP ab Sidekick 2.05 ab Stargazer 2.33 ab Tropical 2.42 ab *Mean separation by pairwise t-tests.05 level.

7 Number of male flowers opened the day of sampling by pollenizer 4 and 6 weeks after planting are presented in Table 7. Early flower production was significantly greater in Accomplice (a special pollenizer) than other pollenizers. The special pollenizers Pollimax and SP5 also produced more male flowers than the standard seeded pollenizers Tropical or SF800. However, on week 6, Pollimax was producing significantly fewer flowers that all but Sidekick. Accomplice contined having high flower production along with SP5, both special pollenizers. The standard seeded pollenizer varieties SF800, Stargazer, and Tropical all were producing high numbers of male flowers in week 6. These survey results indicate that several special pollenizer varieties have better ability to provide pollen for early sets, Accomplice in particular. However, Pollimax was not performing as well for later sets and may be a factor in the reduced fruit numbers seen where used. Table 7. Mean number of male flowers open on day of sampling by pollenizer 4 and 6 weeks after planting. Weeks After Planting Pollenizer 4 6 Flower no. Flower no. Accomplice 6.06 a* a Pollimax 1.42 b 4.50 c SF c ab SP b a Sidekick 0.73 bc 7.63 bc Stargazer ab Tropical 0.40 bc ab *Mean separation by pairwise t-tests.05 level. Seedless vine lengths by week after planting are shown in Table 8 for selected varieties. By 4 weeks after planting, Crunchy Red and Troubadour were larger than 7187 or Fascination. This held throughout the growth period sampled. By week 9, Crunchy Red and Troubadour were over 2 feet longer. A longer reach is advantageous in separate bed pollenizer systems. Table 8. Seedless vine length (inches) by week after planting. Week After Planting Variety inches inches inches inches inches inches inches inches Crunchy Red Fascination Troubadour

8 Seedless fruit numbers by seedless plant crown temperatures are shown in Figure 3. There was a significant linear reduction in the number of fruit carried with an increase in plant temperature measured over the crown from near 3 at 65 F to close to 2 in temperatures above 90 F. In figure 4, seedless fruit numbers in relation to the leaf temperatures of the pollenizers are shown. There also was a significant linear reduction in fruit carried, in this case as pollenizer temperatures increased from 65 F to 95 F fruit number decreased from 3.5 to 1.5. These survey results show that heat stress in both seedless and pollenizer plants has the potential to cause significant yield reductions. Figure 3. Seedless fruit number by seedless plant crown temperature.

9 Figure 4. Seedless fruit number by pollenizer leaf temperature.

10 In Figures 5 and 6, seedless fruit numbers by seedless crown or leaf temperatures for the varieties 7187, Crunchy Red, Fascination, and Troubadour are shown. With crown temperatures, fruit numbers in 7187 were evenly spread from F with little above or below that range. In Crunchy Red, the greatest number of fruits were found with crown temperatures at 75 F but there also with considerable production in the range. In Fascination, there were peaks of fruit carried at 70 and 85 F. Troubadour showed peak fruit numbers at 80 F and considerable production at 75 F. When looking at leaf temperatures and fruit numberss, 7187 peaked at 80 F, Crunchy Red 75 F, Fascination at 70 F and Troubadour at 80 F. Figure 5. Seedless fruit number by seedless plant crown temperature and variety.

11 Figure 6. Seedless fruit number by seedless leaf temperature and variety.

12 Vigor ratings, health ratings, leaf temperatures and crown temperatures for seedless varieties are shown in Table 9 and for pollenizers in Table 10. Troubadour, Liberty, and Fascination had the highest vigor ratings, 7167 and Melody the lowest. There were no differences in health ratings or temperature readings between seedless varieties. With the pollenizers, the highest vigor ratings were with Accomplice and Stargazer, lowest vigor ratings with Pollimax, SF800, SP5, Sidekick, and Tropical. Health ratings which take into account disease incidence and air pollution injury showed that SF800 and Sidekick were the healthiest and Pata Negra, Pollimax, and Tropical had somewhat lower health ratings. There were no overall differences in plant temperatures between pollenizers. Table 9. Mean seedless variety vigor/health ratings and leaf/crown temperatures. Seedless Variety Vigor Health 2 Leaf Temp. 2 Crown Temp 2 Rating 1-10 Rating 1-10 F F c ab Cr. Red 8.24 ab Fascination 8.48 a Liberty 8.50 a Melody 7.97 bc Sugar Heart 8.07 ab Troubadour 8.49 a Mean separation by paired t-tests adjusted by the Tukey-Kramer method, 0.05 level 2 There were no significant differences between varieties in health and leaf/crown temperatures. Table 10. Mean pollenizer vigor/health ratings and leaf/crown temperatures. Pollenizer Vigor Health Leaf Temp. 2 Crown Temp. 2 Rating 1-10 Rating 1-10 F F Accomplice 8.39 a ab Micky Lee 8.16 ab 7.84 bc Pata Negra 8.31 ab 7.44 c Pollimax 7.79 b 7.80 c SF b 8.50 a SP b 7.93 bc Sidekick 8.00 b 8.68 a Stargazer 8.78 a 8.39 ab Tropical 7.44 b 7.50 c Mean separation by paired t-tests adjusted by the Tukey-Kramer method, 0.05 level 2 There were no significant differences between pollenizers with leaf or crown temperatures.

13 Acknowledgements The author gratefully acknowledges: Seasonal Extension Vegetable Program employees Hillary Ennis, Mason Newark, and Lynsey Lofland for on-farm survey data collection. Seasonal Extension IPM Program employees Peggy McDaniel, Cori Killen, and Corryn Barnes for assistance with data collection. Farmer Cooperators: Kevin Evans Jeff Hastings Dave Smoker Eddie and Kyle Steen Gary Calloway Ray Vincent Travis Hastings Mark Collins Doug Corey Danny Magee Jay Rider

14 Appendix A. Weather data for the Georgetown REC site May A B C D E F G H I J K L M N O A Day B Avg Temp ( F) I Avg Solar (MJ.m -2.day -1 ) C Max Temp ( F) J Avg Wind Speed (mph) D Min Temp ( F) K Rainfall (in) E GDD (base 50 F) L Ref ET (in day -1 ) F Avg RH (%) M Avg Soil Temp ( F) G Max RH (%) N Max Soil Temp ( F) H Min RH (%) O Min Soil Temp ( F)

15 Appendix B. Weather data for the Georgetown REC site June A B C D E F G H I J K L M N O A Day B Avg Temp ( F) I Avg Solar (MJ.m -2.day -1 ) C Max Temp ( F) J Avg Wind Speed (mph) D Min Temp ( F) K Rainfall (in) E GDD (base 50 F) L Ref ET (in day -1 ) F Avg RH (%) M Avg Soil Temp ( F) G Max RH (%) N Max Soil Temp ( F) H Min RH (%) O Min Soil Temp ( F)

16 Appendix C. Weather data for the Georgetown REC site July A B C D E F G H I J K L M N O A Day B Avg Temp ( F) I Avg Solar (MJ.m -2.day -1 ) C Max Temp ( F) J Avg Wind Speed (mph) D Min Temp ( F) K Rainfall (in) E GDD (base 50 F) L Ref ET (in day -1 ) F Avg RH (%) M Avg Soil Temp ( F) G Max RH (%) N Max Soil Temp ( F) H Min RH (%) O Min Soil Temp ( F)

17 Appendix D. Weather data for the Georgetown REC site August A B C D E F G H I J K L M N O A Day B Avg Temp ( F) I Avg Solar (MJ.m -2.day -1 ) C Max Temp ( F) J Avg Wind Speed (mph) D Min Temp ( F) K Rainfall (in) E GDD (base 50 F) L Ref ET (in day -1 ) F Avg RH (%) M Avg Soil Temp ( F) G Max RH (%) N Max Soil Temp ( F) H Min RH (%) O Min Soil Temp ( F)