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Abstract
Glasshouse microclimate during 3 growth periods in the Southern Piedmont region of the United States was characterized. An increase in density of tomato plants (Lycopersicon esculentum Mill.) by one-third, which doubled radiation interception, was suggested by early observations. Maintenance of clean glass surfaces was found to be particularly important during cloudy weather. There was no significant difference between mean air temperature and mean rooting media temperature in the raised beds used. CO2 concentration was found to be low (240 ppm) when fans were not circulating outside air. CO2 generators, installed to increase greenhouse CO2 levels, were not effective possibly because control was inadequate. The use of CO2 enrichment requires further study under Southeastern conditions. Relative humidity remained below the recommended 90% in the green-house except during cloudy-mild weather. Although inside relative humidity was generally less than outside relative humidity, values ranged from 90 to 100%.
Abstract
Six sweet potato (Ipomoea batatas (L.) Lam.) lines with a wide range of objectionable fiber content were grown in one location in 1976 and in 2 locations in 1977 to study factors influencing the expression of that trait. We failed to identify environmental factors that would enhance expression of objectionable fiber but did find that large roots tended to have more objectionable fiber than did smaller roots. All roots of high fiber lines did not express objectionable amounts. About 10 US #1 but only 4 jumbo roots of each line would have to be evaluated to have a 95% probability of observing objectionable fiber in high fiber lines. However, Jumbo, US #1 and canning sizes all led to the same relative rankings of lines. Subjective evaluations of baked roots were as effective as objective laboratory tests and could be obtained concurrent with other necessary baking evaluations.
The test involved the use of a control (untreated), an entomopathogenic nematode (Steinernema carpocapsae), a granular insecticide (Dyfonate 2.24 Kg ai/ha) in combination with 7 sweetpotato cultivars having varying levels of resistance and susceptibility to soil insect damage. The parasite was applied three times at monthly intervals (67/cm2). The parasite or insecticide did not reduce root injury by soil insects as compared to the control (untreated). Wireworms, Diabrotica sp. and Systena sp. damage in the resistant cultivars Regal, Southern Delite, Excel and Resisto was less than for the susceptible cultivars (SC–1149-19, Jewel and Centennial). Sweetpotato flea beetle resistance was observed for all cultivars except SC–1149-19 which was susceptible. In this test resistant cultivars were more effective in reducing soil insect damage than the biological or chemical control methods.
The test involved the use of a control (untreated), an entomopathogenic nematode (Steinernema carpocapsae), a granular insecticide (Dyfonate 2.24 Kg ai/ha) in combination with 7 sweetpotato cultivars having varying levels of resistance and susceptibility to soil insect damage. The parasite was applied three times at monthly intervals (67/cm2). The parasite or insecticide did not reduce root injury by soil insects as compared to the control (untreated). Wireworm, Diabrotica and Systena damage in the resistant cultivars Regal, Southern Delite, Excel and Resisto was less than for the susceptible cultvars (SC–1149-19, Jewel and Centennial). Sweetpotato flea beetle resistance was observed for all cultivars except SC–1149-19 which was susceptible. In this test resistant cultivars were more effective in reducing soil insect damage than the biological or chemical control methods.
Abstract
Out of 38 lines of sweet potato [Ipomoea batatas (L.) Lam.] which had demonstrated some resistance in laboratory tests to the sweetpotato weevil, Cylas formicarius elegantulus (Summers), 13 lines had significant levels of resistance, based on weevil free yield in artificially infested fields in Yoakum, Texas. Two lines, W 125 and W 119, previously released as having weevil resistance, maintained a high level of resistance.
Abstract
Field studies were conducted over three seasons to determine the effect of N and K on susceptibility of tomato to bacterial spot. A factorial randomized complete block design consisting of four rates of N (167, 334, 501, and 668 kg·ha–1) and three rates of K (334, 668, and 1335 kg·ha–1) were used. Liquid fertilizer was injected via trickle irrigation. Increasing N rates reduced disease severity, whereas the effect of increasing K was inconsistent from season to season. The concentration of N in leaf tissue showed a significant negative correlation with disease severity, whereas the concentration of Ca in leaf tissue exhibited significant positive correlation with disease severity and negative correlation with N rate during two seasons of data collection.
Abstract
The ‘Resisto’ sweet potato [Ipomoea batatas (L.)Lam.] developed jointly by the U.S. Department of Agriculture, the South Carolina Agricultural Experiment Station, and the Texas Agricultural Experiment Station, combines high yield and excellent baking and canning quality with resistances to disease and insect pests not available in present cultivars.
Abstract
‘Regal’ sweet potato [Ipomoea batatas (L.) Lam.] was developed jointly by the USDA, the South Carolina Agricultural Experiment Station, and the Texas Agricultural Experiment Station. This cultivar has high yield and excellent baking flavor in combination with high levels of resistance to a wide array of diseases and insects.