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J.L. Walworth, D.E. Carling, and G.J. Michaelson

Head lettuce (Lactuca sativa L.) cv. Salinas was produced in field trials in southcentral Alaska with varying planting dates, planting methods, N sources, and N application rates. Variables measured included head weight and diameter and harvest date. Nitrogen source had little effect on head weight. Direct-seeded lettuce produced heaviest beads from early plantings; transplants produced heaviest heads when planted in mid- to late season. Transplanting generally produced heavier heads than direct-seeding. Head weight of transplanted and direct-seeded lettuce was maximized with ≈112 kg N/ha. The data suggest that 112 kg N/ha may be suitable for lettuce direct-seeded or transplanted throughout the growing season.

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Lori D. Calhoun, William S. Conway, and Carl E. Sams

Due to the declining availability of fungicides for use in commercial tomato production, there is a need to investigate alternative disease control methods. Several theories of disease resistance are associated with an increase in plant tissue calcium content, which has increased resistance of tomato seedlings to bacterial wilt and other diseases. Three tomato cultivars (`Mountain Supreme', `Sunrise', and `Celebrity') were grown in a greenhouse hydroponic system to study the role of Ca in reducing decay of fruit by Botrytis cinerea. Calcium treatments of 20, 200, or 1000 ppm were applied in a modified Hoagland's solution. A 3 × 3 factorial randomized complete-block design was used. Mature whole leaves were collected from immediately below the third flower clusters and the calcium content analyzed by inductively coupled plasma emission spectrophotometry. Harvested fruit were inoculated with a 5 × 105 spore/ml conidial suspension of B. cinerea and the decay lesion diameter measured once daily for 7 days. This was repeated for 8 consecutive weeks. Leaf Ca content significantly increased (P < 0.01) as the Ca treatments increased from low to medium (310%) and from medium to high (150%). The medium and high Ca treatments significantly reduced the area of decay caused by gray mold rot (P < 0.01). There were no differences in Ca content or decay among cultivars, and the Ca × cultivar interaction was not significant. It appears that leaf Ca content is negatively associated with resistance of greenhouse-grown tomatoes to gray mold rot, strengthening the hypothesized role of calcium in promoting disease resistance.

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Carl E. Motsenbocker, Marshall D. Sundberg, and Yuehe Huang

Two lines of tabasco pepper (Capsicum frutescens) were previously identified that differ significantly in ease of fruit detachment force. Greenhouse-grown plants of these lines, `McIlhenny Select' and `HP', were investigated for differences in cell organization in the fruit-receptacle area and the separation zone at different developmental stages. Histological examination indicated that fruit of `HP', which requires greater force to separate, exhibited a larger region of sclerified cells within the fruit-receptacle area. In contrast, fruit of `McIlhenny Select', the line that detaches easier, had fewer sclerified cells in this region. Cell sclerification increased for both lines with increasing fruit maturity. The fruit-pedicel separation zone in both lines is distal to the sclerified region and is composed of parenchymatous fruit tissue. The separation zone for `HP' includes at least 10 additional distal cell layers in the fruit septal region than `McIlhenny Select'.

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Renae E. Moran, Dennis E. Deyton, Carl E. Sams, Charles D. Pless, and John C. Cummins

Soybean [Glycine max (L.) Merrill] oil was applied to apple trees [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] as a summer spray in six studies to determine if it controls European red mites [Panonychus ulmi (Koch.)], how it affects net CO2 assimilation (A), and if it causes phytotoxicity. Sprays of 0.5%, 1.0%, and 1.5% soybean oil {TNsoy1 formulation [soybean oil premixed with Latron B-1956 (LAT) spreader-sticker at 10 oil: 1 LAT (v/v)]} reduced mite populations by 94%. Sprays of 1% and 2% soybean oil reduced mite populations to three and four mites per leaf, respectively, compared to 25 per leaf on water-sprayed plants. Soybean oil concentrations of 1.0% and 1.5% applied to whole trees reduced A for less than 7 days. Phytotoxicity did not occur when soybean oil was applied with an airblast sprayer at concentrations of 1.0% and 1.5% or with a mist bottle at 2%. Phytotoxicity occurred when soybean oil was applied with a mist bottle at 4% and 6%, which left soybean oil leaf residues of 0.22 to 0.50 mg·cm-2. No phytotoxicity occurred with 4% SunSpray, which resulted in a mean leaf residue of only 0.13 mg·cm-2. Spraying 1% soybean oil tended to give better mite control than 1% SunSpray Ultra-Fine oil, but caused greater oil residues and a greater reduction in A.

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Joshua D. Klein, William S. Conway, Bruce D. Whitaker, and Carl E. Sams

`Golden Delicious' apples (Malus domestica Borkh.) were treated after harvest with heat (air at 38 °C for 4 days or 42 °C for 1 day) or 2% CaCl2 (w/v; applied as a dip or pressure-infiltrated) or a combination of the two and stored at 0 °C for ≤6 months. Decay caused by Botrytis cinerea Pers.:Fr. after inoculation to a depth of 2 mm with a conidial suspension virtually was eliminated in stored fruit heated at 38 °C, regardless of Ca treatment. Apples punctured to a depth of 0.5 mm (but not 2 mm) and inoculated with B. cinerea on removal from storage were almost completely protected from poststorage decay if they had previously been pressure-infiltrated with 2% CaCl2, regardless of the heat regime. Heating fruit at 42 °C and dipping in 2% CaCl2 were only partially effective in preventing decay from either pre- or poststorage inoculations. Fruit firmness was not related to resistance to decay.

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Joshua D. Klein, William S. Conway, Bruce D. Whitaker, and Carl E. Sams

`Golden Delicious' apples (Malus domestica Borkh.) were treated postharvest with heat (38C/4 d or 42C/24 h) or 2% CaCl2 (applied as a dip or pressure-infiltrated) or a combination thereof and then stored. Decay caused by Botrytis cinerea was virtually eliminated in fruit heated at 38C after inoculation prior to storage, regardless of Ca treatment. Apples inoculated upon removal from storage were almost completely protected from decay if they had been previously pressure-infiltrated with Ca, regardless of heat regime. Heating at 42C or Ca dips were only partially effective in preventing decay. Pressure infiltration of Ca (regardless of heat regime) or heating at 38C (regardless of Ca treatment) resulted in firmer fruit (68 N) than Ca dips or heating at 42C (56 N), which were firmer than nontreated fruit (52 N).

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Raymond L. Hix, Charles D. Pless, Dennis E. Deyton, and Carl E. Sams

The objective of this study was to examine efficacy of soybean oil dormant sprays to manage San Jose scale (Quadraspidiotus perniciosus Comstock) on apple (Malus ×domestica Borkh.). On 14 Feb. 1994 and again on 20 Feb. 1995, `Bounty' apple trees were: 1) left unsprayed (control) or sprayed to runoff with: 2) 3% (v/v) or 3) 6% degummed soybean oil with 0.6% (v/v) Latron B-1956 sticker spreader, or 4) 3% 6E Volck Supreme Spray petroleum oil. Crawler emergence occurred 17 May-28 June, 7 July-30 Aug., and 7 Sept.-24 Oct. 1994. First-generation crawler emergence had started by 8 May in 1995. Both 3% petroleum oil and 6% soybean oil sprays reduced the numbers of first- and second-generation crawlers by 93% in 1994 and first-generation crawlers by 98% in 1995. The 3% soybean oil treatment reduced first- and second-generation crawlers by 60% in 1994 and first-generation crawlers by 83% in 1995. In 1995, apple fruit infestations by first-generation scales on the 3% soybean-, 6% soybean-, and 3% petroleum oil-treated trees did not differ significantly, but all fruit were significantly less infested than the controls.

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Esmaeil Fallahi, William S. Conway, Kenneth D. Hickey, and Carl E. Sams

In several experiments, strong negative correlations were found between fruit and leaf N vs. fruit color and fruit N vs. firmness, but a positive correlation existed between fruit Ca vs. firmness in apples. Based on these relationships, several models were developed to predict postharvest quality using preharvest nutrient status. Quantity and timing of N application to produce optimum-quality fruit in `Delicious', `Fuji', and `Gala' apples have also been investigated. High levels of nitrogen adversely affected fruit quality and increased endogenous ethylene and respiration. In separate experiments, the effects of seven post-bloom CaCl2 applications on various postharvest pathogens were studied in four apple cultivars. Calcium applications did not increase fruit Ca sufficiently enough to reduce colonization or maintain firmness after 4 months of 0C storage, but did slightly reduce infection by these pathogens during the growing season.

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Carl E. Niedziela Jr., Christopher D. Mullins, T. David Reed, William H. Swallow, and Eric Eberly

Pre-cooled bulbs of two dutch iris (Iris ×hollandica) cultivars, Ideal and White Wedgewood, were grown and harvested as cut flowers in four production systems in a tobacco (Nicotiana tabacum) transplant greenhouse from late October until late January in two consecutive production years (2000-01 and 2001-02). All production systems (lily crates, lay-flat bags, pots, and float trays) utilized the same commercial peat-vermiculite, tobacco germination substrate. Stems developed more quickly but were shorter and lighter in 2001-02 than 2000-01 due to warmer growing conditions. Stems grown in float trays were shorter and lighter than other treatments in 2000-01 but similar to the others in 2001-02. Stems grown in lay-flat bags flowered earlier with similar or greater stem lengths and fresh weights as the other systems. Stems of `White Wedgewood' were longer and heavier than `Ideal'. In general, `White Wedgewood' provided more consistent production than `Ideal' in both production seasons. An economic analysis in this study concludes that a grower is unlikely to make money growing dutch iris in a tobacco transplant greenhouse using these production systems unless there is a targeted local market.

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Heather D. Toler, Craig S. Charron, Carl E. Sams, and William R. Randle

Glucosinolates are sulfur-containing secondary plant metabolites commonly found in the family Brassicaceae. The presence of selenium in soils increases the uptake of sulfur and inhibits the production of glucosinolates in brassicaceous plants. This study was undertaken to determine the extent of selenium's impact on sulfur uptake and glucosinolate production in Brassica oleracea L. Rapid-cycling B. oleracea plants were grown hydroponically in half-strength Hoagland's nutrient solution with selenium treatments delivered as sodium selenate concentrations of 0.0, 0.5, 0.75, 1.0, and 1.5 mg·L−1. Elevated sulfur treatments of 37 mg·L−1 sulfate and 37 mg·L−1 sulfate/0.75 mg·L−1 selenate were incorporated to compare with selenium treatments. Plants were harvested and freeze-dried 1 day before anthesis. Selenium and sulfur content of plant tissue was determined by flame atomic absorption spectrophotometry and a carbon–nitrogen–sulfur analyzer. Glucosinolate content of leaf tissue was determined by high-performance liquid chromatography. Selenium and sulfur uptake in plants positively correlated with selenium concentration in the nutrient solution. The sulfur concentration of plants exposed to selenium equaled or exceeded the sulfur concentration of plants exposed to elevated sulfur. Despite higher sulfur concentrations, there occurred a statistically significant decrease in production of five of the seven glucosinolates analyzed in selenium-enriched plants. Plants that underwent elevated sulfur treatments had higher glucosinolate production than selenium-treated plants. These results suggest that selenium either upregulates or prevents the downregulation of sulfur uptake in B. oleracea. In addition, the presence of selenium within the plant appears to have a negative impact on the production of certain glucosinolates despite adequate availability of sulfur.