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John C. Pair and Steven M. Still

Abstract

Three of 6 antitranspirants significantly reduced winter injury 1 of 5 years when applied 1 and 2 times to Ilex × attenuata Ashe ‘Foster's No. 2’. No reduction of winter injury was observed during 1979 and 1980 even though leaf water potentials recorded during winter stress periods indicated that Exhalt 4-10, Vapor Gard, Wilt Pruf, Folicote, and Foligard significantly reduced transpirational loss of water in midwinter. Two applications of Folicote and Exhalt 4-10 increased water potential more than the single fall application, but did not reduce winter injury significantly. Clear Spray did not increase leaf water potential and appeared to crack and peel within 3 weeks aftef application. Scanning electron micrographs indicated better coverage of leaf surfaces by dipping them by spraying and verified the rapid cracking of Clear Spray.

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Thomas M. Todaro and Imed E. Dami

freezing event, with the purpose of enhancing grapevine recovery ( Poling, 2008 ; Zabadal et al., 2007 ). Following winter injury, vine recovery management strategy is a key cultural practice that involves adjustment of pruning and training with the goal

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Hilary A. Sandler

The benefit of applying an antitranspirant for protection of cranberry (Vaccinium macrocarpon Ait.) vines exposed to desiccating conditions was evaluated at four different sites, two sites per year, for a period of 1 year each. Overall, plots receiving one fall application of an antitranspirant produced more berries and greater total fruit mass the following year than did nontreated plots. Overall dry leaf mass was not significantly affected. At one site, treated plots had more flowering uprights and more flowers per upright per unit of ground area than the nontreated plots. For cranberry growers who cannot maintain a winter flood, one fall application of pinolene (Vapor Gard) may offer some protection against winter injury. Further research is needed to document long-term yield effects as well as to clarify the role of the antitranspirant in protecting exposed vines and floral buds against adverse winter conditions. Chemical name used: di-1-p-menthene (pinolene).

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Carlos D. Fear, F. I. Lauer, J. J. Luby, R. L. Stucker, and Cecil Stushnoff

Abstract

Genetic variance components, narrow sense heritability, and combining ability effects of parents were determined for several traits from analysis of a partial diallel cross involving 17 parents. Parents included several Vaccinium species and interspecific hybrids. For fall growth cessation, general combining ability (GCA) effects were variable from year to year, and heritability was low. Variance due to GCA was more important than specific combining ability (SCA) variance for winter injury in each of the years. The heritability estimate over years was low for winter injury, although individual year estimates were higher. Lowbush parents had high GCA effects for winter injury in years with snow cover but low estimates for years without snow cover. Off-season flowering was observed in some progenies in both years studied. Certain V. angustifolium Ait. parents had high GCA effects for the occurrence of off-season flowering. The heritability estimate for off-season flowering in combined years was 0.47. Variation due to years and to GCA × year interaction was significant for all characters studied.

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G.E. Jones and B.M. Cregg

Seventeen Abies species were evaluated for budbreak and frost injury at four locations in Michigan. Freeze tests were conducted on four species growing at the Horticulture Teaching and Research Center to determine cold hardiness levels during winter. Species differed (P ≤ 0.0001) in their days to budbreak at all locations. Trees that had broken bud were more prone to late spring frost damage than trees yet to break bud. Species differed in chlorophyll fluorescence, bud damage, and needle damage after exposure to –44 °C. Bud, foliar, and cambium damage were correlated with chlorophyll fluorescence following freeze tests. Budbreak and midwinter cold hardiness were correlated. Species breaking bud earlier displayed greater midwinter cold hardiness than species breaking bud later. Selection criteria for future Abies introductions to the upper midwestern U.S. should include identifying species with late budbreak to reduce risk of late frost injury.

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Mark P. Widrlechner, Christopher Daly, Markus Keller, and Kim Kaplan

Horticulturists have long recognized that the accurate prediction of winter injury is a key component of the effective cultivation of long-lived woody and herbaceous perennial plants in many climates. Winter injury can limit long-term plant survival

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Norman Pellett and David Heleba

Chopped newspaper at 3.5 and 7.0 kg.m-2 enclosed in white polyethylene sheeting or enclosed in nylon netting at 3.5 kg.m-2 was compared with two layers of 0.64-cm microfoam as winter covering of four taxa of container-grown nursery plants. White polyethylene-enclosed newspaper moderated winter temperatures more than net-enclosed newspaper or two layers of microfoam under white polyethylene. All coverings provided protection against winter injury, as evidenced by container temperature, but net-enclosed newspaper at 3.5 kg.m-2 resulted in a minimal percentage of Daphne burkwoodii `Carol Mackie' plants with three or more shoots longer than 2 cm in the spring. Gaillardia grandiflora, covered by newspaper during winter, had less spring growth than plants covered by microfoam, but all coverings provided protection for Juniperus horizontalis `Prince of Wales' and Physostegia virginiana.

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G. J. Keever, G.S. Cobb, and W.J. Foster

Plant response to time of transplanting from 0.53-qt (OS-liter) to l-gal (3.8-liter) containers was influenced by cultivar and severity of winter. Transplanting of `Formosa' from Sept. through Dec. 1983 resulted in injury and death of many plants due to a low temperature of 8F (-13.3C) in Dec. 1983. Injury or death of `Hino Crimson' was higher when plants were transplanted in December. Survival and growth indices of both cultivars were higher when transplanted in January through March. During 1986-87, when minimum temperature was 26F (-3.3C), transplanting between September and April had minimal effect on growth of `Formosa', but plant quality was better when plants were transplanted between December and April. Transplanting date had little effect on size of `Hino Crimson', except smaller plants were produced when transplanted in April; quality was highest of plants transplanted from November through March.

Open access

M. N. Westwood and H. O. Bjornstad

Abstract

Effects of cultivars, rootstock, and long-term growth regulator and herbicide treatments on above-ground tree damage from a December 1972 freeze were recorded soon after the freeze and again 7 years later. Ultimate injury was greatest with ‘Jonared’ and least with ‘Golden Delicious’ apple (Malus domestica Borkh.) in the growth regulator plot, while in the herbicide plot it was opposite for the 2 cultivars. There was not a good relationship between injury to specific plant parts (flower buds, spurs, leaders, and lower trunks) observed soon after the freeze, and ultimate tree mortality. Growth regulator treatments significantly increased freeze damage to flowers and spurs, but ultimate tree mortality was reduced by daminozide sprays. Clean cultivation increased flower and spur mortality but did not reduce yield or increase tree mortality compared to the sod treatment. Trees on Mailing (M) 5, M 7 and M 9 rootstocks showed greater initial trunk injury than those on seedling roots, but only those on M 9 showed significantly greater ultimate mortality.

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R. E. C. Layne and C. S. Tan

Abstract

The effects of irrigation and tree density on peach [Prunus persica (L.) Batsch cv. Harken/Siberian C] production were investigated over 11 years. Irrigation improved growth of peach trees, lowered levels of winter injury and perennial canker (Leucostoma spp.), and promoted tree survival. Annual and cumulative marketable yields were increased, especially in the later years. Tree density did not affect perennial canker, winter injury, or tree survival. Reducing tree spacing increased resulted total growth per hectare and annual and cumulative marketable yields. Irrigation and density treatments usually did not interact and had an additive effect on growth and fruit production. The most productive management system (a combination of 50% available soil moisture and 536 trees/ha) resulted in accumulated yields over 8 years of 179 tonnes (t)/ha comparted with only 74 t/ha for the check treatment (no irrigation and 266 trees/ha).