An experiment was conducted during 2005 and 2006 in Kinston, NC, with the objective of maximizing triploid watermelon [Citrullus lanatus (Thunb.) Matsum. and Nak.] fruit yield and quality by optimizing the choice and use of pollenizers. Treatments were pollenizer cultivars planted singly [‘Companion’, ‘Super Pollenizer 1’ (‘SP1’), ‘Summer Flavor 800’ (‘SF800’), and ‘Mickylee’] or in pairs (‘Companion’ + ‘SP1’, ‘Companion’ + ‘SF800’, and ‘SP1’ + ‘SF800’). All pollenizers from these seven treatments were interplanted with the triploid cultivar Tri-X-313. Planting arrangement was compared by establishing ‘SF800’ in a hill versus an interplanted field arrangement. Effect of pollenizer establishment timing on triploid fruit yields and quality was evaluated by establishing ‘SP1’ 3 weeks after planting and comparing it with the establishment of ‘SP1’ at the time of triploid plant establishment. Finally, a triploid planting with no pollenizer (control) was included to determine pollen movement. Fruit yield from the control was 22% or less of yield of the other treatments containing a pollenizer and less than 10% in the initial or early harvests. Pollen movement was minimal among plots and differences in yield and fruit quality could be attributed to pollenizer treatment. In 2005, the use of ‘Companion’, ‘SP1’, or ‘Mickylee’ as pollenizers produced similar total yields, whereas ‘SF800’ produced the lowest yield. In 2005, ‘Companion’ produced more large fruit than the other individual pollenizer treatments. Combining the pollenizers generally did not enhance triploid yields or quality. Interplanting of pollenizers consistently resulted in greater yield compared with the hill system. Late planting of ‘SP1’ increased the incidence of hollow heart in the marketable fruit and decreased yield compared with simultaneously planting ‘SP1’ and triploid plants. Thus, selection of pollenizer, planting arrangement, and time of pollenizer establishment are all important considerations to optimizing triploid yield and quality.
Peter J. Dittmar, David W. Monks, and Jonathan R. Schultheis
Peter J. Dittmar, Jonathan R. Schultheis, and David W. Monks
Pollen from triploid (seedless) watermelon ( Citrullus lanatas) is nonviable. Diploid (seeded) watermelons are required in seedless watermelon production for pollination and fruit set. In 2004, markets continued to increase for triploid watermelon but decrease for diploid watermelons. Seed companies are commercializing diploid cultivars (pollenizers) specifically designed as a pollen source for triploid watermelon production. The objectives of this research were to characterize the vegetative, floral, and fruit growth and development of these pollenizers. Five cultivars were evaluated: `Companion', `Mickylee', `Mini Pool', `SP-1', and `Jenny'. When measuring the longest vine, `Companion' produced the smallest plants reaching a maximum vine length of 183 cm, 31 days after transplant (DAT). `Mickylee', `Mini Pool', `SP-1', and `Jenny' had similar vine lengths reaching maximum lengths ranging 294–335 cm, 31 DAT. The compact growth of `Companion' is consistent with the shorter node length of 3.8 cm, while the other pollenizers had a node length of 9.9–10.9 cm. `SP-1' produced more male flowers than the other pollenizers beginning 24 DAT and produced 30–40 male flowers per plant per day, 31–55 days after transplant. `Mickylee', `Mini Pool', and `Jenny' produced 9–15 male flowers per plant per day, 24–55 days after transplant. Early production of male flowers by `Companion' was similar to `Mickylee', `Mini Pool' and `Jenny'; however, flower production became the lowest compared with all pollenizer cultivars 24 DAT. `SP-1' produced more female flowers resulting in the most fruit production (4 fruit per plant). In contrast, `Companion' produced the fewest female flowers and produced 2 fruit per vine. `Mickylee' had the largest fruit weighing 5.9 kg, and `SP-1' and `Jenny' produced the smallest fruit weighing 3.1 kg. The use of specific pollenizers may provide the opportunity to customize production for specific cultivars for either early and or late harvests.
Jialin Yu, Nathan S. Boyd, and Peter J. Dittmar
In Florida, cabbage (Brassica oleracea L.) is typically grown without a plastic mulch and as a result, weeds are a significant problem in most fields. Experiments were conducted from Nov. 2015 to Apr. 2016 in Balm, Citra, and Parrish, FL, to evaluate weed control and ‘Bravo’ cabbage tolerance to multiple herbicide programs applied pretransplanting (PRE-T), posttransplanting (POST-T), PRE-T followed by (fb) a sequential application at 3 weeks after transplanting (WATP), and POST-T fb sequential application at 3 WATP. PRE-T herbicide treatments of 277 g a.i./ha clomazone, 280 g a.i./ha oxyfluorfen, and 798 g a.i./ha pendimethalin and POST-T herbicide treatments of 6715 g a.i./ha dimethyl tetrachloroterephthalate (DCPA) were ineffective, and weed control never exceeded 70% in Balm and provided <50% weed control in Citra and Parrish at 6 and 8 WATP, respectively. POST-T applications of napropamide + S-metolachlor at 2242 + 1770 g a.i./ha, DCPA + S-metolachlor at 6715 + 1170 g a.i./ha, and S-metolachlor POST-T fb clopyralid at 1170 g a.i./ha fb 210 g ae/ha were the most effective herbicide treatments and consistently provided >70% weed control. In addition, results showed that all of the herbicide treatments evaluated except the PRE application of clomazone at 277 g a.i./ha are safe for cabbage with no adverse effect on yield.
Peter J. Dittmar, David W. Monks, and Jonathan R. Schultheis
Triploid (seedless) watermelon [Citrullus lanatus (Thunb.) Matsum. and Nak.] pollen is nonviable; thus, diploid (pollenizer) watermelon cultigens are required to supply viable pollen for triploid watermelon fruit set. The objective of this research was to characterize maximum potential vegetative growth, staminate and pistillate flower production over time, and measure exterior and interior fruit characteristics of pollenizer cultigens. Sixteen commercially available and numbered line (hereafter collectively referred to as cultigens) pollenizer and two triploid cultigens were evaluated in 2005 and 2006 at Clayton, NC. Vegetative growth was measured using vine and internode length, and staminate and pistillate flower development was counted weekly. Fruit quality and quantity were determined by measuring individual fruit weights, soluble solids, and rind thickness. Based on vegetative growth, pollenizer cultigens were placed into two distinct groups. Pollenizers, which produced a compact or dwarf plant were ‘Companion’, ‘Sidekick’, ‘TP91’, ‘TPS92’, and ‘WC5108-1216’. Pollenizers having a standard vine length were ‘Jenny’, ‘High Set 11’, ‘Mickylee’, ‘Minipol’, ‘Pinnacle’, ‘Summer Flavor 800’ (‘SF800’), ‘Super Pollenizer 1’ (‘SP1’), and ‘WH6818’. Cultigens with compact growth habit had shorter internodes and vine lengths compared with the cultigens with standard growth habit. Cultigens with the greatest quantity of staminate flower production through the entire season were ‘Sidekick’ and ‘SP1’. The lowest number of staminate flowers was produced by ‘TP91’ and ‘TPS92’. Based on fruit quality characteristics and production, pollenizers currently or possibly marketed for consumption include ‘Mickylee’, ‘SF800’, ‘Minipol’, ‘Jenny’, and ‘Pinnacle’. The remaining cultigens evaluated in this study should be used strictly as pollenizers based on fruit quality. Arrangement of diploid pollenizers in a commercial planting of triploid watermelons is an important consideration depending on plant vegetative development. Based on staminate flower production, cultigens with higher staminate flower production are potentially superior pollenizers and may lead to improved triploid quality and production. Furthermore, pollenizer selection by fruit characteristics should include a rind pattern easily distinguished from triploid fruit in the field.
Peter J. Dittmar, David W. Monks, Jonathan R. Schultheis, and Katherine M. Jennings
Most seedless watermelons are grown on black polyethylene mulch to aid crop establishment, growth, yield, and quality and weed control. However, nutsedge is a persistent problem in this production system, as it can easily penetrate the mulch. Halosulfuron-methyl is registered in some crops and provides excellent yellow nutsedge control. The objective of this research was to determine the effects of reduced halosulfuron-methyl contract to the watermelon plant on fruit yield and quality. The seedless watermelon cultivars, Tri-X-313 and Precious Petite, were transplanted into black polyethylene mulch and sprayed 16 days later. Halosulfuron-methyl at 35 g a.i./ha plus 0.25% (v/v) nonionic surfactant was applied at 187 L·ha–1 with a TeeJet 8002 even tip nozzle. Treatments were no spray, 25% of the vine tips, 25% of the crown, and over the top (entire plant). Plants in each treatment were rated (0% = no damage, 100% = fatality) for herbicide injury and the longest vine was measured on four plants. The no-spray treatment had the longest vines (156 cm). The topical halosulfuron treatment resulted in the shortest vines (94 cm) and the highest visual damage rating (63%). The herbicide caused foliage to yellow, internodes to shorten, and stems to crack. Treatments receiving halosulfuron-methyl applied to 25% of the vine (tip end) or 25% of the vine (crown end) resulted in reduced injury compared to the topical application. Generally, the 25% vine tip application was the safest halosulfuron treatment. The total yield (kg·ha–1) and number of watermelons/ha were similar among treatments. The no-spray treatment produced 4450 kg·ha–1 and 8300 watermelons/ha. The over-top treatment produced 3500 kg·ha–1 and 7300 watermelons/ha. Watermelon in the no-spray treatment weighed 4.4 kg, while watermelons weighed 3.9 kg with the over the top treatment. Halosulfuron-methyl is registered to apply to middles between watermelon rows; however, topical applications are prevented due to the possibility of crop injury. This research suggests that reduction of topical application to only 25% contact of the crop may improve crop tolerance. Thus application to nutsedge patches where limited contact to watermelon occurs may be a possibility in the future.
Charles E. Barrett, Lincoln Zotarelli, Lucas G. Paranhos, Peter Dittmar, Clyde W. Fraisse, and John VanSickle
Weather has a major influence on cabbage (Brassica oleracea var. capitata L.) production. Variation in yield between years and cropping seasons is common in North America. Cabbage in Florida has historically been cultivated on bare ground with seepage irrigation. The objectives of this study were to compare yield and profit of a bare ground cabbage production system used in Florida with an alternative plasticulture system. Data from various cabbage trials were combined by production system and used to create regression equations that predicted yield based on air temperature and solar radiation that were significantly correlated with yield. The regression equations were then simulated with correlated stochastic air temperature and solar radiation to estimate the yield distributions for both systems. Cabbage price ($/Mg fresh) was stochastically simulated (correlated to yield) to be used in the profit model. The profit model was created by using the product of yield and the price per unit yield minus fixed and variable costs associated with production and marketing. Simulated profit for bare ground and plasticulture was used to estimate their respective distributions to provide a tool for making better management decisions in the presence of risky weather conditions. The plasticulture system was estimated to have a 36% higher cost but a 57% higher profit than the bare ground system. This is, in large part, because the simulated mean yield for the bare ground system was 29.7 Mg·ha−1 compared with 54.4 Mg·ha−1 for plasticulture. These findings confirmed that plasticulture is an economically viable best management practice for cabbage production in Northeast Florida.
Charles E. Barrett, Lincoln Zotarelli, Lucas G. Paranhos, Brian S. Taylor, Peter Dittmar, Clyde W. Fraisse, and John VanSickle
Florida is a major fresh-market cabbage (Brassica oleracea L. var. capitata) producing state in the United States. The current cabbage production system relies on bare ground and subirrigation that requires a large volume of water to irrigate the crop. The bare ground system facilitates a maximum of 48,438 plant/ha, while there is a potential to increase plant population per area using plasticulture and drip irrigation. The objectives of this study were to determine the optimum cabbage plant population and plant arrangement that maximizes marketable yield per area for a high cabbage population plasticulture system. Cabbage was grown on 1.2-m-wide raised beds with black plastic mulch and drip irrigation. Plants were grown in either three or four rows with in-row plant spacings ranging from 15 to 35 cm and plant populations ranging from 41,518 to 129,167 plants/ha. Cabbage marketable yield increased as in-row spacing increased. Yields ranged from 19.7 to 69.7 Mg·ha−1. Marketable yield was not different between 3 and 4 rows for in-row spacings above 25 cm. The 15 and 20 cm in-row spacing produced significantly lower yields in the 4-row configuration as compared with the 3-row configuration in Fall and Winter 2011. Wider in-row spacings produced a greater percentage of heads of marketable size while reducing the percentage of small heads when compared with narrower in-row spacings. Mean head weight increased as in-row spacing increased and a 3- or 4-row configuration with an in-row spacing between 25 and 30 cm had consistently high yields in all three seasons compared with narrower in-row plant spacings. These results indicated that with a high population plasticulture system variable plant populations could be selected. In-row plant spacings between 30 and 35 cm may be beneficial for early plantings while a 25-cm spacing could be more productive for later plantings, especially when weather conditions are favorable.
Peter J. Dittmar, Jonathan R. Schultheis, Katherine M. Jennings, David W. Monks, Sushila Chaudhari, Stephen Meyers, and Chen Jiang
The reason for internal necrosis occurrences in sweetpotato (Ipomoea batatas) storage roots is not well understood. This disorder begins internally in the storage roots as small light brown spots near the proximal end of the root that eventually can become more enlarged as brown/black regions in the cortex. The objective of this study was to determine the effect of ethephon and flooding on the development of internal necrosis in the sweetpotato cultivars Beauregard, Carolina Ruby, and Covington over storage durations from 9 to 150 days after harvest (DAH) when roots had been cured. Soil moisture treatments were no-flooding, and simulated flooding that was created by applying 10 inches of overhead irrigation during 2 weeks before harvest. Ethephon was applied at 0, 0.75, and 0.98 lb/acre 2 weeks before harvest. Overall, ‘Covington’ and ‘Carolina Ruby’ had greater internal necrosis incidence (22% to 65% and 32% to 51%, respectively) followed by ‘Beauregard’ (9% to 22%) during storage duration from 9 to 150 DAH at both soil moistures. No significant change was observed for either internal necrosis incidence or severity for ‘Beauregard’ and ‘Carolina Ruby’ over the storage duration of 9–150 DAH. However, there was an increase of internal necrosis incidence and severity 9–30 DAH in ‘Covington’, with incidence and severity remaining similar 30–150 DAH. Storage roots in treatments sprayed with 0.75 or 0.98 lb/acre ethephon had higher internal necrosis incidence and severity compared with the nontreated, regardless of cultivars at both soil moistures. This research confirms that sweetpotato cultivars differ in their susceptibility to internal necrosis (incidence and severity), ethephon applied to foliage can contribute to internal necrosis development in storage roots, and internal necrosis incidence reaches a maximum by 30 DAH in ‘Covington’ and 9 DAH in ‘Carolina Ruby’ and ‘Beauregard’.