The Dominican Republic is located in the Hispaniola Island in the Caribbean region. Its climate differs substantially over short distances and is the most diverse of the Caribbean. Annual average temperature is 25 °C, ranging from 18 °C (at higher elevations) to 28 °C (at sea level). Average annual rainfall is 1500 mm. Although sugar, coffee, cocoa, and tobacco are the principal cash crops of the country, peppers are increasing in popularity on the country’s exportation market. Bell peppers grown in high tunnels and greenhouses may be impacted by high temperatures that result in reduced fruit yield and quality. In this article, we make a short review of cooling techniques for high tunnels and share the experience of training bell pepper growers and extension personnel from the Dominican Republic regions of San José de Ocoa and Constanza on how to manage heat stress of bell peppers grown inside high tunnels. Bell pepper plants inside high tunnels showed symptoms of heat stress, including reduced plant and fruit size, small fruit number, and a mild leaf chlorosis. In both regions, but particularly in the warmer region, San José Ocoa, because of occurrences of high temperatures inside the high tunnels, growers were advised to use well-ventilated high tunnels, such as structures with plastic film on the top and screen net on the sides. Other strategies such as shade nets (30% to 40% shade) placed on top of the high tunnel or whitewash paint applied on the high tunnel cover may also help reduce air and soil temperatures inside the tunnel. Use of white or silver reflective mulch, instead of the commonly used black mulch, may provide additional reduction of soil temperature. In conclusion, high tunnel structures developed for temperate regions, with limited to poor ventilation, may result in excessively high temperatures inside the high tunnels and thus were not recommended for the Dominican Republic regions of this study. More research is necessary on adequate high tunnel design and cooling techniques for high tunnel production, particularly in tropical regions.
Juan Carlos Díaz-Pérez and Erick Smith
Elizabeth Conlan, Tatiana Borisova, Erick Smith, Jeffrey Williamson, and Mercy Olmstead
Freeze events between January and April can result in major crop and economic losses for growers of low-chill, early-ripening varieties of blueberry (Vaccinium sp.) in Florida and Georgia. The objective of this research was to determine current responses by blueberry growers to freeze events. Blueberry growers in Florida and Georgia were surveyed about frost protection decision criteria. Growers had differing opinions on when to make the decision to frost-protect blueberry crops. Almost all (98.9%) of the respondents (n = 94) who reported using at least one method of active frost protection reported using irrigation. Farm size, as measured by blueberry acreage, did not influence decisions regarding the use of active frost protection measures. Blueberry growers, on average, reported that a loss of up to 30% to 39% of their crop could be tolerated and still produce a marketable crop. However, they may have been overly cautious at the early bud stages, with ≈40% and 55% of respondents protecting at the bud swell and tight cluster stages, respectively. Understanding the use of irrigation as a frost protection practice in the southeastern United States can aid in improving frost protection recommendations, helping growers maximize yield and saving water and money.
Tekan S. Rana, Erick D. Smith, Cain Hickey, and Mark Hoffmann
More than 3000 acres of commercial muscadine (Vitis rotundifolia) vineyards exist in the southeastern United States. The muscadine wine industry is generating an economic impact of $1 billion in North Carolina alone. Muscadines have been cultivated since the 1800s, but muscadine vineyard fertilizer programs, tissue sampling, and nutrient sufficiency ranges continue to be based on anecdotal knowledge. While seasonal changes in tissue nutrient concentration are well documented in bunch grape (Vitis vinifera), questions remain about the seasonal and cultivar-dependent dynamics of muscadine leaf tissue nutrient concentrations. The aim of this study was to assess temporal and cultivar-related differences in tissue nutrient concentration of mature commercially grown muscadines. Leaf tissue nutrient concentration of the muscadine cultivars Carlos and Noble were assessed in three vineyards (Piedmont North Carolina, north Georgia, and south Georgia) at bloom, véraison, and postharvest in 2018 and 2019. Our results show that nitrogen (N), phosphorus (P), and manganese (Mn) were generally above the recommended sufficiency ranges, with calcium increasing over the season—and N, P, and potassium decreasing over the season. ‘Carlos’ had significantly higher levels of N and P, compared with ‘Noble’, while ‘Noble’ showed higher Mn concentration than ‘Carlos’. With this evaluation, we demonstrate the need for a modification in muscadine tissue nutrient sufficiency ranges that are based on cultivar and vine growth stage.
Juan C. Díaz-Pérez, Dan MacLean, Smiljana Goreta, Sarah Workman, Erick Smith, Harwinder Singh Sidhu, Gunawati Gunawan, Anthony Bateman, Jesús Bautista, William Lovett, Maja Jukić Špika, Gvozden Dumičić, and Mira Radunić
Pomegranate (Punica granatum L.) is a nonclimacteric fruit sold fresh as whole fruit or arils (fleshy seeds). It is also used for the production of juice, wine, and syrup. Pomegranate is popular due to its numerous health benefits. In the United States, it is grown primarily in California and other semi-arid regions, with Wonderful being the most widely grown cultivar. However, preliminary research has shown that ‘Wonderful’ produces low yields in Georgia, thus indicating the need to identify cultivars better suited for warm and humid conditions, such as those of the southeastern United States. The objective of this study was to determine the physical and chemical quality attributes of pomegranate cultivars grown in Georgia. Pomegranate fruit from 40 cultivars were harvested during 2012 to 2017. Individual fruit weight varied from 124 g for ‘Utah Sweet’ to 631 g for ‘C1’. The total fruit weight percentage accounted for by fresh aril weight (aril fraction) ranged from 22% for ‘C8’ to 70% for ‘JC’. Individual aril weight ranged from 174 mg for ‘Utah Sweet’ to 638 mg for ‘Cloud’. Across cultivars, individual fruit weight increased linearly with the increasing number of arils. Aril color varied from white to deep red. The arils L* value ranged from 15.7 (dark arils) for ‘Crown Jewel’ to 46.1 (light arils) for ‘Utah Sweet’. The a* values ranged from 0.6 (white arils) for ‘Cloud’ to 20.5 (red arils) for ‘Crab’. The b* values ranged from 8.7 for ‘DJ Forry’ (from a store) to 62.5 for ‘R9’. The Chroma* values ranged from 13.4 for ‘Cloud’ to 24.3 for ‘Crab’. The hue° values ranged from 29.7 for ‘Wonderful’ (from a store) to 87.1 for ‘Cloud’. Rind color was related to the color of the arils; high a* values in the rind and arils were associated with the red color. The fruit juice content ranged from 174 mL·kg−1 fruit for ‘Utah Sweet’ to 638 mL·kg−1 fruit for ‘Cloud’. Cultivars varied from tart to sweet. The fruit soluble solids concentration (SSC) ranged from 10.8% for ‘Sin Pepe’ to 16.4% for ‘Crown Jewel’. Fruit titratable acid (TA) ranged from 0.27% for ‘Sin Pepe’ to 6.20% for ‘Utah Sweet’. The juice maturity index measured as the SSC/TA ratio ranged from 1.9 for ‘Utah Sweet’ to 39.5 for ‘Sin Pepe’. The juice total phenols (measured as gallic acid equivalents) ranged from 463 mg·L−1 for ‘JC’ to 2468 mg·L−1 for ‘Wonderful’ (Georgia). Trolox equivalent antioxidant capacity values of juice ranged from 10,001 µM for ‘King’ to 59,821 µM for ‘I11’. Cupric reducing antioxidant capacity values in juice ranged from 7471 µM for ‘Azadi’ to 20,576 µM for ‘Wonderful’ (Georgia). Juice total anthocyanins varied from 1.7 mg·L−1 for ‘R19’ to 50.0 mg·L−1 for ‘Wonderful’ (Georgia). Pomegranate cultivars showed large variability in physical and chemical attributes. Such pomegranate variability represents opportunities for breeding, for the retail market, and for the development of different products by the food industry.