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Kathleen Demchak

High tunnels are a relatively economical form of protected culture, and offer cultural advantages such as protection from the elements and an extended production season. Interest in high tunnels for small fruit production has been increasing in North America. Growers in the United States and Canada are using multi-bay and single-bay high tunnels for production of red raspberry (Rubus idaeus), black raspberry (Rubus occidentalis), blackberry (Rubus subgenus Rubus), strawberry (Fragaria ×ananassa), and blueberry (Vaccinium spp.). Research trials using high tunnels are being conducted in numerous places across the United States. In most instances, high tunnels increased yields of berry crops, improved quality, and decreased the incidence of most diseases compared with field production, powdery mildew (Sphaerotheca macularis) being a notable exception. The insect and mite complex encountered in tunnels when growing berry crops has changed markedly, often becoming similar to that which might have been expected in greenhouses, with numbers of two-spotted spider mite (Tetranychus urticae), whitefly (Aleyrodidae), and thrips (Frankliniella spp.) reaching high levels without control measures. In studies at The Pennsylvania State University, primocane-bearing cultivars of red raspberry plants produced at least two to three times as much marketable fruit in tunnels as in a previous field study, with substantial summer and fall crops obtained. ‘Triple Crown’ thornless blackberry produced very high marketable yields in the tunnels, even though winter injury historically resulted in a lack of blackberry production in the field. Strawberry production in a plasticulture system using short-day or day-neutral cultivars was found to be viable; however, the primary benefit of high tunnels for strawberry may have been reliability of production rather than a yield increase. Potential reasons for improvements in productivity and quality are numerous and warrant further attention.

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David S. Conner and Kathleen Demchak

Strawberry (Fragaria ×ananassa) and caneberries (Rubus sp.) are popular crops that can bring revenue to farms and may improve farm profitability. High and low tunnels can bring a number of benefits to growers, including season extension and improved berry yield and quality, as well as management challenges. Few studies in the literature report directly on grower experiences using tunnels. We report the results of interviews of 10 independent growers who use tunnels to produce strawberries and caneberries. The results echo previous studies finding improved yield and quality, and highlight benefits and challenges around pest, weed, and nutrient management. One novel finding is the role of season extension in creating marketing opportunities. Interviewed growers caution of a learning curve and the need to start on a small scale and grow gradually. Future focus for research should include improved ventilation and mechanization.

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Barbara L. Goulart and Kathleen Demchak

While the Pennsylvania wine industry was established early in the history of the European settlement in the state, the current industry was spawned relatively recently by virtue of the Pennsylvania Winery Act in 1968. The industry is widely distributed, with wineries and wine grape production throughout the state, however the primary center of production is in southeastern Pennsylvania, where climatic conditions allow for the production of some of the hardier European wine grapes. A second, much smaller cluster of production is along Lake Erie, within the zone of more temperate weather induced by the lake. A third region is scattered throughout the harsher environments of the rest of the state. These regions are characterized not only by climatic differences, but by differences in producer demographics, clientele, pest complexes, cultivar preferences and obstacles to production. The industry is built primarily on French-American hybrid production, however European grapes are being produced, are in demand, and as such, are commanding relatively high prices.

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Graham Sanders, Elsa Sanchez and Kathleen Demchak

The increased demand for organic and sustainably grown produce has resulted in a demand for information on organic and biorational fungicides. The efficacy of these fungicides is often not established, yet they are aggressively advertised. In 2005 the efficacy of six organic and biorational fungicides and two controls were evaluated on field-grown red raspberries (Rubus idaeus `Prelude' and `Nova') for gray mold (Botrytis cinerea) management. Phytotoxicity of the fungicide treatments was evaluated on a weekly basis following each fungicide application. Fruit was harvested by hand, sorted into marketable and unmarketable categories and weighed. Subsamples of fruit were evaluated for postharvest disease development. Data analysis showed `Nova' was more susceptible to phytotoxicity than `Prelude'. The application of Phostrol resulted in the highest phytotoxicity rating when compared to all other fungicide treatments. The water spray control, standard fungicide (Captan/Elevate rotation) control, Endorse, and Lime Sulfur treatments resulted in negligible phytotoxity ratings. Applying Milstop, Milstop + Oxidate, and Oxidate + Vigor Cal Phos resulted in similar intermediate phytotoxicity ratings. Differences in marketable yield were nonexistent for the two cultivars and eight fungicide treatments. The predominant diseases observed in the postharvest evaluations were gray mold, blue mold (Penicillium sp.), and rhizopus soft rot (Rhizopus sp.) and/or mucor mold (Mucor sp.). This evaluation will be repeated in 2006.

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Maria E. Cramer, Kathleen Demchak, Richard Marini and Tracy Leskey

Insecticides are the primary tool raspberry growers use to control Japanese beetles (Popillia japonica), but reliance on pesticides is costly and there are risks to nontarget species. Based on observations that Japanese beetles were less abundant on raspberries in high tunnels than in fields, we investigated the effects of plastic films that transmit different amounts of ultraviolet (UV) light to Japanese beetles. Many insects are sensitive to light in the UV-A range and use it for navigation. High-tunnel plastics that block varying percentages of UV radiation are increasingly available. We grew two primocane-fruiting red raspberry cultivars, Polka and Josephine, in tunnels with six different covering treatments. Five were plastics that blocked the UV range to varying degrees, and one was a no-plastic treatment. In 2016, beetles were counted and removed from the plants by hand daily. In 2017, beetles were removed by hand every 4 to 5 days. Foliage temperature was measured in each tunnel twice in 2017 with an infrared (IR) thermometer. Spectral transmittance characteristics of the plastics were measured with a spectroradiometer in 2015 and 2018. Mean beetle counts by date and for the whole season were compared for the plastics and cultivars. Japanese beetle numbers were significantly greater in the no-cover treatment than in all plastic treatments. The plastic that blocked more than 90% of the UV-A range usually had significantly lower beetle populations than the plastics that blocked the least UV-A. Overall, it appears that using a UV-blocking plastic can reduce Japanese beetle aggregation and feeding damage on raspberries, decreasing the need for other control. This could benefit growers by reducing the cost of insecticides and decreasing exposure risk for nontarget organisms.

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Wei Qiang Yang, Barbara L. Goulart and Kathleen Demchak

A factorial experiment was conducted to determine the effect of aluminum (0 and 600 μM) and media (sand, and 1:1 sand:soil) on mycorrhizal (M) and non-mycorrhizal (NM) highbush blueberry plantlets. There were no differences in nutrient uptake and total plant dry weight between M and NM plantlets. However, more root growth, as determined by dry weight, was observed in M than NM plantlets. The plantlets growing in sand had more dry weight than did those in the soil medium. Although the root growth and shoot growth were reduced by the 600-μM Al treatment, the direct effect of Al on plantlet growth was not clear due to Al and P interactions. Plant nutrient uptake was reduced by high concentrations of Al, suggesting that high Al concentration limited the ability of roots to acquire most of the nutrients. Mycorrhizal epidermal cell infection levels of 15% to 20% were maintained in the roots in soil medium but decreased to about 5% over the 6 weeks of the experiment in the sand medium. Although M plantlets accumulated more Al in their roots, Al was readily transported to the leaf tissues of M and NM plantlets.

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Wei Qiang Yang, Barbara L. Goulart and Kathleen Demchak

Aluminum and P interactions were investigated in mycorrhizal (M) and nonmycorrhizal (NM) highbush blueberry plantlets in a factorial experiment. The toxic effects of Al on highbush blueberry were characterized by decreased shoot, root, and total plant dry weight. Many of the negative effects of Al on plant root, shoot, and total dry-matter production were reversed by foliar P and N application, indicating P or N uptake were limited by high Al concentration. However, Al mediated growth reduction in P-stressed plants suggested that the restriction of P uptake by high Al may not have been the only mechanism for Al toxicity in this experiment. Root Al and P concentration were negatively correlated in NM plantlets but not in M plantlets, suggesting mycorrhizal infection may alter P uptake processes. Al uptake also was affected by M infection, with more Al accumulating in M plantlet roots and leaves. Correlations among foliar ion concentrations were also affected by M fungal infection.