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Eric J. Hanson

Foliar B sprays (500 mg·liter-1) had increased the B content of apple (Malus domestics Borkh), pear (Pyrus communis L.), plum (Prunus domestics L.), and cherry (Prunus cerasus L.) leaves 90%) to 185% 3 days after treatment. Boron levels in treated apple, pear, and plum leaves decreased to levels similar to nontreated leaves by 9 days after application, whereas cherry leaves required 33 days to approach levels in nontreated leaves. Movement of applied B was also studied by treating cherry leaves with B solutions enriched in the stable isotope, 10B. Isotope analysis indicated that applied B moved out of leaves and into subtending tissues. The highest concentrations of applied B were found in buds, followed by bark and wood.

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Eric J. Hanson

The effects of multiple calcium (Ca) sprays on berry quality of mature `Bluecrop' plants was tested for two seasons. In 1992, treatments supplied a total of 0, 1.0, 1.9 or 3.8 kg Ca/ha, in five applications between 18 June and 16 July. Calcium was applied as CaCl2. Concentrations for the highest rate ranged from 0.08% Ca in the first spray to 0.2% in the last. In 1993, treatments included a control, 12.1 kg Ca/ha applied as CaCl2, 24.2 kg Ca as CaCl2, and 12.1 kg Ca as the commercial product Nutrical (CSI Chem., Bondurant, IA). Seven sprays were applied between 4 June and 16 July, using concentrations of 0.1% to 0.4% Ca. Treatments had no effect on the percentage of soft or rotten berries, berry firmness, or Ca concentrations in berries in either year. Leaf Ca levels were increased slightly by higher application rates.

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Eric J. Hanson

Calcium sprays were applied to `Bluecrop' highbush blueberry bushes between petal fall and fruit harvest. In 1992, bushes received five sprays between 18 June and 16 July that totaled 0, 1.0, 1.9 or 3.8 kg Ca/ha. Calcium was applied as CaCl2 at spray concentrations of 0.08% to 0.2% Ca. Treatments in 1993 consisted of a control; 12.1 and 24.2 kg Ca/ha as CaCl2; and 12.1 kg Ca/ha as the commercial product Nutrical. Calcium was applied in seven sprays between 4 June and 16 July using spray concentrations of 0.1% to 0.4% Ca. Berry samples were hand-picked, stored for 3 to 20 days, and evaluated. Treatments had no effect on the percentage of soft or rotten berries, berry firmness, or berry Ca concentrations during either year. Calcium applications increased leaf Ca concentrations. Chemical names used: calcium trihydroxyglutarate (Nutrical).

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Eric Hanson and Annemiek Schilder

Twenty cranberry (Vaccinium macrocarpon) genotypes were evaluated for five seasons in an experimental upland planting in southwest Michigan. Beds were constructed on a silty clay loam soil by excavating to grade, and filled with 30 to 45 cm of sand. Four 2 × 2-m plots of each genotype were planted in 1996. Fruit were harvested with hand scoops from 2000 to 2005. Yield per plot, average berry weight, and percent berries exhibiting decay were determined. Sound fruit were also stored at 2 °C for 4 to 8 weeks and sorted to determine the percentage of fruit developing decay in storage. Fungi were isolated and identified by morphological characteristics. Genotypes producing the highest average yields were `Stevens', `Ben Lear', #35, `LeMunyon', and `Franklin'. Varieties with the highest average berry weight were `Pilgrim', `Stevens', `Baines', `Beckwith', `Searles', and #35. Genotypes with lower rot incidence at harvest were #35, `Early Black', and `Foxboro Howes', whereas `Howes' and #35 developed the least rot during storage. Fungi commonly isolated from decaying fruit were Colletotrichum sp., Coleophoma empetri, Phomopsis vaccinii, Phyllosticta vaccinii, Fusicoccum putrefaciens, Botrytis cinerea, Pestalotia sp., and Allantophomopsis sp. Prevalence of specific fungi differed among cranberry genotypes.

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Philip Throop and Eric Hanson

Absorption of 15N-enriched fertilizer by young `Bluecrop' bushes was compared following application of the nitrification inhibitor dicyandiamide (DCD). Ammonium sulfate solutions containing 7.9 g N (10.2 atom % 15N) were applied to the soil surface. Treated plants received 0.6 g of DCD and were compared to fertilized untreated controls. Fruit was collected during the growing season and bushes were excavated at the end of the season. The bush was partitioned into root stems and current season's growth (shoots, leaves, fruit). Tissues were dried, ground, and analyzed for 15N and 14N by mass spectrometry. No significant differences in N absorption were observed. Available soil fertilizer nitrate and ammonium content is presently being analyzed for effects of DCD.

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Eric J. Hanson

Seven trials were conducted over 3 years in several Michigan locations to study the response of sour cherry (Prunus cerasus L. cv. Montmorency) to foliar B sprays. Orchards ranged in age (6 to 12 years) and leaf B concentrations (19 to 32 μg B/g dry weight). Treatments consisted of a 500 mg B/liter spray applied to leaves in late September or early October, and an untreated control. Boron sprays increased B concentrations in dormant buds and flowers by 94% and 54%, respectively, but did not consistently change leaf levels. Boron applications increased fruit set and production by as much as 100% in one trial, but had no effect in others. Fruit set and production were most consistently increased in trees containing leaf B levels of 19 to 25 μg·g–1 dry weight. In trees with leaf B concentrations of 25 to 32 μg·g–1, responses to B were less consistent and smaller in magnitude.

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Eric J. Hanson

Field trials were conducted in 1988 and 1989 in several Michigan locations to determine if fruit set and yield of sour cherry (Prunus cerasu s L. cv `Montmorency') can be increased by boron (B) applications. Orchards varied in age (6-12 years) and initial leaf B concentrations (18-32 ppm dry weight). Treatments consisted of an unsprayed control and B sprays (500 ppm B) applied to the leaves in Sept. Fall B sprays increased B concentrations in flowers the following spring by 50-100%. The percentage of flowers which set fruit was either unaffected by sprays or increased by as much as 100%.. Fruit yields were unaffected by B sprays in some trials, and increased by as much as 100% in others. No visual symptoms of B deficiency were observed. Results of 1990 trials will also be presented.

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Steven F. Berkheimer and Eric Hanson

Injury has been observed since the early to mid-1990s to highbush blueberries (Vaccinium corymbosum L.) growing along roads in southern Michigan. Symptoms include shoot dieback, flower bud mortality, and reduced yields. To determine if this injury was the result of deicing salts applied to roads, salt (sodium chloride, NaCl) spray was applied to potted blueberry plants, and to the plant root zones. Bushes sprayed six times during the winter with NaCl solutions (0, 0.034, 0.068, 0.137, 0.274, 0.548 m) developed the same injury symptoms observed in roadside fields, and injury severity was proportional to the spray concentration. The root media of other potted plants was saturated with NaCl solutions (0, 0.017, 0.051, 0.154, and 0.462 m) in Mar. 2002. Pots were then rinsed with fresh well water when growth began in April to determine if soil salt caused similar damage. The highest soil salt levels killed most above ground growth, and damage diminished with decreasing salt levels. Twigs were also excised from branches sprayed twice with NaCl solutions or water and frozen incrementally to measure the temperature resulting in 50% flower bud mortality (LT50). Salt exposure reduced the LT50 of flower buds, by as much as 11.5 °C, relative to the control, even within 2 days of treatment. Additional studies with chloride salts (NaCl, KCl, CaCl2, MgCl2) and sodium salts (NaCl, Na-acetate, Na2SO4) indicated that most reduced the cold tolerance of blueberry flower buds to some degree.

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Eric Hanson, Brent Crain and Joshua Moses

Red raspberry cultivars that produce fruit on current season canes (primocanes) can produce additional fruit the following year on floricanes. The primocane-fruiting raspberries ‘Himbo Top’, ‘Joan J’, and ‘Polka’ were grown organically in high tunnels and pruned to different floricane densities to determine the effects on fruit yield (primocane, floricane, total) and harvest times. Floricane densities were 0, 2.4, or 4.8 canes per meter of row length in 2015, and 0, 4.9, or 9.8 canes per meter in 2016 and 2017. Total yield (floricane plus primocane) was significantly greater with low floricane density (17 t·ha−1) or high density (19 t·ha−1) compared with no floricanes (12 t·ha−1). Floricane density did not affect primocane yield or harvest times. Primocanes of ‘Polka’ were taller when floricanes were present, but primocanes of other cultivars were unaffected. Results indicate that producing fruit on both primocanes and floricanes (double cropping) can improve sustainable overall yields.