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C. M. Mainland and P. Eck

Abstract

Gibberellic acid (GA) at 0, 5, 50, 200 and 500 ppm was applied to the highbush blueberry, var. ‘Coville,’ for 3 consecutive fruiting periods in the greenhouse. Application to the flower was a prerequisite for parthenocarpic fruit set and development. No significant differences were found in the number of shoots formed, shoot length, and stem or trunk diameter. GA caused a significant reduction in the number of flower buds formed for the next crop.

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C. M. Mainland and P. Eck

Abstract

An effective growth regulator treatment for inducing fruit set and parthenocarpic development in the highbush blueberry would restore a number of once productive varieties to profitable commercial use. The decline in productiveness of varieties such as Coville, Earliblue and Jersey has paralleled the decline in native pollinating insects such as the bumblebee (4). The use of commercial honeybees has not solved the fruit set problem in many cases because the problem varieties appear to be less attractive to the domesticated bees than are the fruitful varieties (4).

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Paul Eck and C. M. Mainland

Abstract

Various flower parts were measured from 35 different cultivars and selections of highbush blueberry and correlated to their fruit setting capability. High fruit set was associated with a short distance between stigma and anther tip. The ideal flower from the standpoint of max fruit set appears to be one with a short corolla that widened at the middle to more than 8 mm and then narrowed perceptibly at the base. It is suggested that flower structure might serve the plant breeder as an additional criterion for evaluating the potential fruit setting capability of a blueberry selection.

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C. M. Mainland and P. Eck

Abstract

Gibberellic acid (GA) at 0, 50, 100, 250 and 500 ppm was applied to the highbush blueberry var. ‘Coville’ at bloom for 2 consecutive seasons in the field. Percentage fruit set was increased by all GA treatments in 1966. In 1967 yields were increased by the 100, 500 and 500 ppm caged treatments. GA-treated plants produced smaller berries that required a longer maturation period but were still of fresh market quality. The smallest and latest maturing fruit were seedless and were produced from caged plants receiving GA. No differences in mold incidence and percentage weight loss in storage were apparent between treated fruit and the control. Only fruit from caged plants receiving 500 ppm GA had refractive index values less than those of the control berries. The GA treatments did not reduce the number of flower buds formed in 1966 or 1967.

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S.D. Rooks, J.R. Ballington, and C.M. Mainland

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G. A. Cummings, C. M. Mainland, and J. P. Lilly

Abstract

Growth and yield of rabbiteye blueberries (Vaccinium ashei Reade cv. Tifblue) decreased as soil pH was raised from 4.5 and 7.0. Plant survival decreased at pH 6.0 and 6.5 and all bushes died at pH 7. After 3 growing seasons, bushes were sacrified, plots split, and S added to lower pH to 5.00 or weathered sawdust was added to all plots and the experiment replanted. Replanted bushes in the sawdust plots were greener and produced greater linear growth during the first growing season. Sawdust, even the first year, overcame the harmful effects of high initial soil pH except at pH 7. Optimum growth and production resulted from incorporated sawdust at initial soil pH 5.0. Addition of S was less effective than sawdust in overcoming the harmful effects of high soil pH.

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J.R. Ballington', C.M. Mainland, S.D. Rooks, A.D. Draper, and G.J. Galletta

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J.R. Ballington, C.M. Mainland, S.D. Duke, A.D. Draper, and G.J. Galletta

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E. P. Boyer, J. R. Ballington, and C. M. Mainland

Abstract

Ericoid mycorrhizae were measured on roots of wild and cultivated highbush blueberries (Vaccinium corymbosum L.) from 7 locations in southeastern North Carolina over 4 sampling dates. An adequate clearing and staining procedure was developed specifically for observing endomycorrhizae in blueberry roots. Abundant mycorrhizae were found in wild blueberry plants, but few mycorrhizae were noted in cultivated plants. Phosphorus levels were lower in the wild than in the cultivated blueberry soils at most locations.

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J. J. Baron, T. J. Monaco, and C. M. Mainland

Abstract

Hexazinone was applied as a soil drench to 1-year-old rooted hardwood cuttings of highbush (Vaccinium corymbosum L.) and rabbiteye (V. ashei Reade) blueberries in a series of greenhouse experiments. No differences in susceptibility to hexazinone were detected among 10 highbush and 3 rabbiteye cultivars growing in a fine sand soil. Two highbush and 2 rabbiteye cultivars were assayed for hexazinone tolerance in low, medium, and high organic matter soil which contained 1.3%, 3.5%, and 49.5% organic matter, respectively. Hexazinone at 1 or 2 kg/ha had no inhibitory effect on blueberry growth in the high organic matter soil, inhibited growth slightly on the medium organic matter soil and caused severe injury in the low organic matter soil. At rates of 4 and 8 kg/ha, injury was severe on the medium and low organic matter soils but very slight on the high organic matter soil.