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J. Harrison Ferebee IV, Charles W. Cahoon, Michael L. Flessner, David B. Langston, Ramon Arancibia, Thomas E. Hines, Hunter B. Blake and M. Carter Askew

Chemical desiccants are commonly used to regulate tuber size, strengthen skin, and facilitate harvest for potato (Solanum tuberosum) production. Glufosinate is labeled for potato vine desiccation; however, limited data are available. Saflufenacil, a protoporphyrinogen oxidase–inhibiting herbicide, is an effective desiccant in other crops. Field research was conducted to evaluate glufosinate and saflufenacil as desiccants applied to ‘Dark Red Norland’ potato. Desiccants consisted of diquat, glufosinate, saflufenacil, glufosinate plus carfentrazone, and glufosinate plus saflufenacil applied at three timings, DESIC-1, DESIC-2, and DESIC-3, when size B potatoes averaged 43%, 31%, and 17% of total potato weight. Potato vine desiccation was more difficult at DESIC-1 and DESIC-2 because of immature vines. Diquat was the most effective desiccant 7 days after treatment (DAT), desiccating potato vines 88% at DESIC-1 7 DAT. Glufosinate alone desiccated potato vines 65% at the same timing; however, carfentrazone and saflufenacil added to glufosinate increased vine desiccation 8% and 16% compared with glufosinate alone, respectively. Vine desiccation by all treatments ranged 99% to 100% at 14 DAT. Desiccant and timing effects on skin set were determined using a torque meter before harvest. Skin set resulting from all desiccants and timings ranged between 1.88 and 2 lb-inch, and no significant differences were observed. No significant differences in yield were noted among desiccants. This research indicates that glufosinate and saflufenacil are suitable alternatives to diquat for potato vine desiccation; however, safety of saflufenacil applied to potatoes before harvest has not been determined.

Open access

Heidi C. Anderson, Mary A. Rogers and Emily E. Hoover

Consumer demand for local and organic strawberries (Fragaria ×ananassa) is increasing. Growers who can meet this demand have a competitive edge in the direct-to-consumer market. Innovations in strawberry production for northern climates offer new opportunities for growers to meet the demand for local organic strawberries. Typically adopted for season extension, the use of poly-covered tunnels for crop protection provides other benefits including protection from adverse weather. Low tunnels are easy to install, low cost, temporary protective structures that are well-adapted for annual day-neutral strawberry production, and they are more space efficient than high tunnels for these low-stature crops. A range of specialty tunnel plastics that modify and diffuse light are available, but there is little information on how these influence strawberry plant growth and performance in the field. Our objectives were to determine the effects of experimental ultraviolet blocking and transmitting plastics on light and microclimate in low tunnel environments and assess differences in fruit yield and quality in the day-neutral strawberry cultivar Albion in an organic production system. This research was conducted on U.S. Department of Agriculture-certified organic land over 2 years, in 2016 and 2017. We found that ultraviolet intensity and daily light integral (DLI) were lower in covered plots than in the open field. Maximum daily temperatures were slightly higher in covered plots. Both ultraviolet-blocking and ultraviolet-transmitting plastics improved marketable fruit yield compared with the open-field control. Strawberries grown in the open-field treatment were lower in chroma than covered plots in 2017, and there was no difference in total soluble solids between treatments in either year. Low tunnel systems allow for increased environmental control and improved fruit quality and are well-adapted for day-neutral organic strawberry production systems.

Open access

Sangho Jeon, Charles S. Krasnow, Gemini D. Bhalsod, Blair R. Harlan, Mary K. Hausbeck, Steven I. Safferman and Wei Zhang

Pythium species incite crown and root rot and can be highly destructive to floriculture crops in greenhouses, especially when irrigation water is recycled. This study assessed the performance of rapid filtration of recycled irrigation water for controlling pythium root rot of poinsettia (Euphorbia pulcherrima) in greenhouses. Two greenhouse experiments investigated the effect of filter media type (sand and activated carbon), fungicide application (etridiazole), and pathogen inoculum source (infested growing media and infested irrigation water). Rapid sand filtration consistently controlled pythium root rot of poinsettia. Significant improvements in height, weight, root rot severity, and horticultural quality were observed for the plants in the sand filter treatment, compared with the inoculated control plants. However, the activated carbon filter removed essential nutrients from the irrigation water, resulting in plant nutrient deficiency and consequently leaf chlorosis, thus reducing plant weight, height, and horticultural quality. The etridiazole application did not completely prevent root infection by Pythium aphanidermatum, but plant weight, height, and horticultural quality were not negatively affected. P. aphanidermatum spread from infested growing media to healthy plants when irrigation water was recycled without filtration. Rapid sand filtration appears to have the potential to limit the spread of P. aphanidermatum that causes root rot of greenhouse floriculture crops.

Open access

Zongyu Li, R. Karina Gallardo, Wendy Hoashi-Erhardt, Vicki A. McCracken, Chengyan Yue and Lisa Wasko DeVetter

Pacific Northwest North America (PNW) strawberry (Fragaria ×ananassa) growers are transitioning away from the processing to fresh-market sector in response to changes in local and regional markets. However, many of the regional cultivars bred for the PNW were not developed for the fresh market. There is a need to gain a better understanding of growers’ priority traits and their relative importance to enable breeders, researchers, and extension specialists to better serve this growing industry. The objective of this study was to provide such information on strawberry genetic traits of importance for the changing strawberry industry in the PNW with an emphasis on fresh-market production. Six surveys were administered to 32 growers representing ≈53%, 23%, and 15% of the total strawberry acreage in Oregon, Washington, and British Columbia, Canada, respectively. Growers ranked the relative importance of five plant and fruit traits, including fruit quality, disease resistance/tolerance, insect pest resistance/tolerance, plant stress tolerance, and other plant factors. Information about target markets, marketing channels, and general grower characteristics were also obtained. Whereas overall responses differed among the surveyed locations, fruit quality was considered the most important trait across all locations, with disease resistance/tolerance as the second most important. Specific fruit quality traits of importance were external appearance free of defects, skin color, size, sweetness, firmness, and flavor, whereas phytonutrients, seed color, and low drip loss after freezing and thawing were less important. Plant stress tolerance was identified as less important for strawberry growers in all locations. Results also showed many growers have already or are in the process of transitioning to the fresh market. Information obtained from this survey can be leveraged to target important breeding traits for fresh-market strawberry breeders within the PNW. Results also suggest priority areas of synergistic research and outreach activities to help growers achieve high fruit quality while managing diseases for fresh-market producers.

Open access

John M. Ruter

Carolina laurel cherry (Prunus caroliniana) is native to the U.S. southeastern coastal plain from North Carolina westward to eastern Texas. The species has been planted extensively in the southeast as an ornamental tree or hedge. Unfortunately, carolina laurel cherry naturalizes readily and is now found in a variety of habitats, both natural and disturbed. Flowering occurs in the late winter/early spring before new leaves emerge and fruit ripens in the fall/winter. Fruit is eaten by migratory birds and seed is dispersed. Seedlings readily germinate in the understory of forests and landscapes in the spring. As there are a limited number of cultivars available, selections with improved form and sterility are needed for the landscape trade. In 2008, seed was collected and treated with Cobalt-60 gamma irradiation at rates ranging from 0 to 150 Gy. The lethal dose killing 50% of the seedlings (LD50) was between 50 and 100 Gy. Three sterile plants were selected in 2012 from the M1 (first generation of mutagen-treated seedlings) population totaling 62 seedlings. M2 (second-generation seedlings from M1 parents) seed was collected Fall 2012, and 1509 seedlings were grown to flowering size in containers. In 2014–15, 120 seedlings that showed no fruit production were planted in the field in Watkinsville, GA, for further evaluation. Ratings on field-grown plants in Dec. 2017 and 2018 showed that 73% and 78% of the plants, respectively, produced no fruit, whereas the remaining plants had minimal to heavy fruit set. Because carolina laurel cherry is andromonoecious, production of male and bisexual flowers was evaluated on 17 selections in 2018. Of 500 flowers evaluated per selection, the number of male flowers per plant ranged from 22 to 415 (4.4% to 83%). The number of racemes with all-male flowers on each selection ranged from 1 to 32. There were no significant correlations between the number of male flowers or number of all-male flowered racemes per plant and production of fruit. Approximately 5% of M2 seedlings remain seedless after 6 years of growth.

Open access

Michael A. Schnelle

Five woody species, black locust (Robinia pseudoacacia), yaupon holly (Ilex vomitoria), black cherry (Prunus serotina), snailvine [Cocculus carolinus (formerly Menispermum carolinum or Epibaterium carolinum)], and southern waxmyrtle [Morella cerifera (formerly Myrica cerifera)], are all native to Oklahoma and nearby states. They all have varying levels of use in and importance to the United States nursery industry. Past natural habitats and where these plants have spread to date, either intentionally or naturally, are discussed here. These native plants have migrated to or have become increasingly dominant in regions of the continental United States because of prolific fruit loads dispersed by birds and mammals, anthropogenic disturbances, overgrazing pastures, and certain species’ tolerance of environmental extremes. Potential control measures include chemical applications, timely cultivation, heightened awareness of grazing practices, and prescribed burning.

Open access

Neil O. Anderson

Historic ignorance of species’ native range, expansion due to unintentional involvement by vectors, and their quiet evolution has caused several invasive species to become “poster children,” such as purple loosestrife (Lythrum salicaria), reed canarygrass (Phalaris arundinacea), and others. Common misconceptions on how these became problematic have involved a variety of causes, including ignorance of species’ ability to intercross and create introgressive hybrids, lack of insects for control, wind pollination, and intercontinental distribution from their native range. Current research focuses on how misappropriating the historical contexts can reverse our misconceptions of native species being noninvasive and how this affects control by land managers. Purple loosestrife and reed canarygrass will be used as example species to demonstrate challenges that native vs. exotic, intra-, and interspecific differences confer to land managers. Issues such as a lack of phenotypic differences challenge land managers’ charge to control invasive individuals yet retain the noninvasives. This is fraught with challenges when native vs. exotic status is invoked or cultural values are entwined. To avoid a monumental impasse, particularly when native and exotic types are phenotypically indistinguishable, this dilemma could be solved via modern techniques using molecular biology.

Open access

Jennifer L. Parke, Neelam R. Redekar, Joyce L. Eberhart and Fumiaki Funahashi

Phytophthora species cause crop losses and reduce the quality of greenhouse and nursery plants. Phytophthora species can also be moved long distances by the plant trade, potentially spreading diseases to new hosts and habitats. Phytosanitary approaches based on quarantines and endpoint inspections have reduced, but not eliminated, the spread of Phytophthora species from nurseries. It is therefore important for plant production facilities to identify potential sources of contamination and to take corrective measures to prevent disease. We applied a systems approach to identify sources of contamination in three container nurseries in Oregon, California, and South Carolina. Surface water sources and recaptured runoff water were contaminated with plant pathogenic species at all three nurseries, but one nursery implemented an effective disinfestation treatment for recycled irrigation water. Other sources of contamination included cull piles and compost that were incorporated into potting media, infested soil and gravel beds, used containers, and plant returns. Management recommendations include preventing contact between containers and contaminated ground, improving drainage, pasteurizing potting media ingredients, steaming used containers, and quarantine and testing of incoming plants for Phytophthora species. These case studies illustrate how recycled irrigation water can contribute to the spread of waterborne pathogens and highlight the need to implement nursery management practices to reduce disease risk.