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  • Author or Editor: Bhabesh Dutta x
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Onions (Allium cepa) are typically planted late fall and harvested in spring in the Vidalia, GA, USA, region. Onions grown here are renowned for their for sweetness and are marketed to consumers as Vidalia onions. High rainfall during the relatively long growing season (4 to 5 months) may result in nitrogen (N) leaching during production. Therefore, fertilizer applications are usually aligned with stages of crop development to ensure nutrient availability for the entire season. Although the impacts of N application rate have been previously investigated for Vidalia onion production, the optimal timing for the final N application of the season has not been determined. The objectives of this study were to determine the optimal timing of the last fertilizer N application (at bulb initiation, during bulb growth, or during bulb maturation) in conjunction with the impact of three N application rates (75, 105, and 135 lb/acre N) on yield and quality in Vidalia onion. Soil N levels were affected by N rate, year, and onion growth stage. In 2020, up to 135 lb/acre N was required to maximize onion yields, and in 2021, onion yields were unchanged among N fertilizer treatments. Final N applications at bulb initiation resulted in greater yields than applications made during bulb growth or bulb maturation. In addition, as the N rate increased and the time of final application occurred later in bulb development, pungency values increased. Incidence of sour skin (Burkholderia cepacia) and center rot (Pantoea sp.) diseases were greater in 2020 compared with 2021 and seemed to be affected by environmental conditions more than N fertilization.

Open Access

Large populations of sweetpotato whiteflies (Bemisia tabaci) have become more regular occurrences during the fall months in parts of the southeastern United States. Large populations of sweetpotato whiteflies have resulted in a significant increase in the incidence of sweetpotato whitefly-transmitted viruses, particularly the cucurbit leaf crumple virus (CuLCrV), which has the potential to cause complete yield loss of fall-planted yellow squash and zucchini (Cucurbita pepo). This study evaluated commercial cultivars of yellow squash and zucchini for resistance against CuLCrV and estimated the yield and fruit quality under environmental conditions during the fall growing season in the southeastern United States. A factorial experimental design was conducted with nine yellow squash and 11 zucchini cultivars during Fall 2017, Fall 2018, and Fall 2019 in Tifton, GA. In situ weather stations monitored the weather conditions during growing seasons, and yellow pest monitor cards monitored the sweetpotato whitefly populations in 2018 and 2019. During all growing seasons, yellow squash and zucchini plants were rated weekly for the severity of CuLCrV. Harvests were conducted 12 times during each season, and fruit were graded as fancy, medium, and culls. Rainfall distribution directly affected the sweetpotato whitefly populations during the production year. In 2018, frequent rainfall events created field conditions that reduced the sweetpotato whitefly populations compared with those during 2017 and 2019. The severity of CuLCrV negatively impacted both the yield and quality of fruit of yellow squash and zucchini, and no resistant commercial cultivars of yellow squash or zucchini were identified. Nonetheless, the yellow squash cultivars Lioness, Gold Prize, and Grand Prize, and the zucchini cultivars SV6009YG and SV0914YG had the highest yields when subjected to the highest sweetpotato whitefly populations during the study.

Open Access

A range of organic fertilizers are available for vegetable crops; however, there is a lack of information regarding the performance and rates of organic fertilizers commonly used in the production of Vidalia onion (Allium cepa). Two commercial organic fertilizers, a mixed source organic fertilizer [MIX (10N–0.9P–6.6K)] and a pelleted poultry litter [PPL (5N–1.8P–2.5K)], were evaluated in two soil types at application rates of 0, 100, 150, 200, 250, and 300 lb/acre nitrogen (N) to determine their impact in the production of Vidalia onions in Georgia, USA, with the objective of determining an optimal fertilizer source and application rate. Field trials were conducted in the 2019–20 and 2020–21 growing seasons in Watkinsville, GA, USA (Cecil series sandy clay loam soil) and Tifton, GA, USA (Tifton series loamy sand soil) on certified organic land. There were significant interactions among location, year, and fertilizer application rate for total marketable yield. In Watkinsville, total marketable yields of onions at different N rates ranged between 1320 and 4565 lb/acre in 2019–20, and between 9951 and 28,749 lb/acre in 2020–21. In Tifton, total marketable yields ranged from 3776 to 9264 lb/acre and 7094 to 14,066 lb/acre in the 2019–20 and 2020–21 seasons, respectively. Aboveground onion N accumulation at harvest was affected by an interaction among location, study year, and fertilizer rate. The largest plant N accumulation was in Watkinsville in 2020–21, ranging from 26 to 50.8 lb/acre N in the 0- and 300-lb/acre N treatments, respectively. In 2020, there were no differences in soil inorganic N at harvest between plots receiving the MIX (9 lb/acre N) or PPL (9.8 lb/acre N) in either location. In 2021, soil inorganic N was greater in plots receiving the MIX fertilizer (14.8 lb/acre N) compared with the PPL fertilizer (11.2 lb/acre N). Yields increased linearly with additional fertilizer; therefore, an optimal application rate for organic fertilizers was not determined.

Open Access

The use of resistant cultivars against Xanthomonas campestris pv. campestris (Xcc) is considered a critical management practice for black rot (BR) management in cabbage (Brassica oleracea var. capitata). Although most studies that have evaluated resistance to BR were conducted in greenhouses without accounting for yield, there is a clear need to investigate cultivar performance under field conditions. The objectives of this study were to evaluate commercial cabbage cultivars for resistance to BR and determine yield and head quality under field conditions. Field experiments with eight cultivars (Acclaim, Bravo, Capture, Celebrate, Cheers, Melissa, Monterey, and TCA-549) were conducted in two cabbage growing seasons, Fall 2018 and Spring 2019. Fields were spray-inoculated with Xcc (3 × 105 cfu/mL) at 35 and 49 days after transplanting in Fall 2018 and Spring 2019, respectively. Cabbage BR severity was evaluated at weekly intervals starting from 7 days postinoculation (DPI) until harvest. Marketable and unmarketable yields and cabbage head quality were measured at harvest. Cabbage BR symptoms were detected in all tested cultivars for both growing seasons with initial symptoms observed as early as 28 and 21 DPI in Fall 2018 and Spring 2019, respectively. Severity of cabbage BR at harvest was significantly greater in Fall 2018 compared with Spring 2019, whereas marketable yield was significantly higher in Spring 2019 (45,169 lb/acre) compared with Fall 2018 (26,370 lb/acre). In both growing seasons, ‘TCA-549’ had the lowest severity of BR and ‘Melissa’ had the highest severity of BR. Area under the disease progress curve (AUDPC) was 175 and 13 for ‘TCA-549’ in Fall 2018 and Spring 2019, respectively. The AUDPC for ‘Melissa’ in Fall 2018 and Spring 2019 were 2376 and 905, respectively. Regardless of growing season, cabbage marketable yield was higher for ‘Acclaim’ (51,760 lb/acre) compared with all other cultivars; however, there was no significant difference between Acclaim and TCA-549 (42,934 lb/acre) for cabbage marketable yield. Cabbage marketable yield was the lowest for cultivars Melissa (18,275 lb/acre) and Capture (24,236 lb/acre). Overall, there was a significant correlation between BR disease severity and cabbage marketable and unmarketable yields. Increasing the BR severity decreased cabbage marketability due to an increase in unmarketable yields. Continued development of cultivar resistance to BR is important for cabbage production in the southeastern United States, given the favorable conditions for disease development. The use of cultivars with low susceptibility, pathogen-free seeds, crop rotation, and proper spraying programs should be considered the best management practice for BR disease.

Open Access

Summer squash (Cucurbita pepo L.) is a major vegetable crop produced in Georgia and Florida during the fall season. This production is vulnerable to whitefly (Bemisisia tabaci Genn.)-transmitted viruses that lead to severe yield losses. Over the past several years, whitefly populations have increased during the fall, thus leading to an increase in whitefly-transmitted viruses such as Cucurbit leaf crumple virus (CuLCrV) and Cucurbit yellow stunting disorder virus (CYSDV). Whitefly management for summer squash relies on the use of insecticides and can be costly without providing adequate management of the viruses. Deployment of host resistance to whiteflies and their transmitted viruses (CuLCrV and CYSDV) is the best strategy for mitigating yield loss of summer squash; however, no resistant cultivars are commercially available. In the current study, resistance or tolerance to whiteflies, CuLCrV, and CYSDV was determined for squash germplasm from the U.S. Department of Agriculture (USDA) Germplasm Resources Information Network (GRIN), university breeding programs, and commercial companies in Georgia and Florida across 2 years. In both locations and years, visual virus symptom severity scores were collected and a quantitative polymerase chain reaction (qPCR) was used to determine the CuLCrV viral load and CYSDV presence in Georgia. Whitefly-induced feeding damage was evaluated by directly assessing the intensity of silverleaf symptoms and visual counts of whitefly adults on the foliage in the field or in photographs. Virus symptom severity was lower in C. moschata Duchesne ex Poir. genotypes, namely, PI 550689, PI 550692, PI 550694, PI 653064, and Squash Betternut 900, than in other evaluated genotypes. Two C. pepo accessions were common between both locations for viral severity (PI 442294) or viral severity and viral load (PI 171625). Lower CuLCrV loads were identified in C. ecuadorensis Cutler & Whitaker (PI 540895), and C. okeechobeensis (Small) L.H.Bailey (PI 540900) than other evaluated genotypes. Four genotypes tested negative for CYSDV during both years: C. pepo (PI 507882), C. moschata (PI 483345), C. ecuadorensis (PI 390455), and C. okeechobeensis (PI 540900); they are potential sources of resistance. Six C. moschata accessions (PI 211999, PI 550690, PI 550692, PI 550694, PI 634982, and PI 653064) showed high tolerance to silverleaf disorder and had the lowest adult whitefly counts. Collectively, the accessions identified in the current study are potential sources of resistance or tolerance to whitefly and whitefly-transmitted viruses (CuLCrV and CYSDV).

Open Access