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M. N. Westwood and H. O. Bjornstad

Abstract

Considerable work has been done on the effects of gibberellins on parthenocarpic set and growth of apple fruits. Bukovac (1) has reviewed the literature in this field and has presented further evidence that seedless fruits induced to set by gibberellins A3 and A4 (GA3 and GA4) are distinctly more elongate than normal seeded fruits. More recently Dennis and Edgerton (2) found that GA made seeded fruits of one variety of apple more elongate than controls, although shape was not altered on several other varieties. Westwood and Blaney (6) reported several factors other than applied GA that also affected apple shape. Among these were crop density (i.e. leaf: fruit ratio), varietal strain, cluster position, and rootstock. To further study the effect of GA on fruit shape without confounding it with seedlessness, a test was set up using seeded fruits in which crop density and rootstock were held constant.

Open access

M. N. Westwood and H. O. Bjornstad

Abstract

Repeated winter rain or water soaking in the laboratory reduced the time required for breaking winter rest of ‘Bartlett’ pear (Pyrus communis L.) and ‘Starkrimson’ apple (Malus domestica Borkh.). Possibly a water soluble inhibitor is leached from the buds.

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.

Open access

M. N. Westwood and H. O. Bjornstad

Abstract

Tests with pear on P. communis L. and ‘E. M. Quince C’ (Cydonia oblonga Mill.) rootstocks showed that early fruit thinning to 1 fruit per cluster increased ultimate % fruit set of ‘Comice’; thinning to 2 fruits per cluster did not increase ultimate set Limb girdling 3 weeks after bloom did not effectively increase set, but when used in combination with cluster thinning, increased ‘Anjou’ set beyond either treatment alone. Heading-back pruning of ‘Comice’ on ‘Quince C’ in a high density plot increased both fruit set and ultimate yield relative to thinning-out pruning.

Open access

M. N. Westwood, P. B. Lombard, and H. O. Bjornstad

Abstract

Tree survival beyond 2 years of intergeneric pear/apple graft combinations depended on the scion cultivar, the use of ‘Winter Banana’ apple interstock, and the specific rootstock. Trees with ‘Cornice’ scion and ‘Winter Banana’ interstem (on all six stocks) had higher survival (27%) after 11 years than those with ‘Bartlett’ scion (12%). No ‘Cornice’ tree on apple rootstock survived without the ‘Winter Banana’ interstem. Tree survival with ‘Winter Banana’ interstem after 11 years was 73% on M.26, 14% on M.7 and M.9 EMLA, 7% on MM.106 and MM.111, and 0% on M.9. Only trees of ‘Bartlett’ and ‘Cornice’ on M.26 and ‘Cornice’ on M.7 with ‘Winter Banana’ interstems produced fruit through the 11th year. Tree size ranged from 10% of standard for ‘Bartlett’ on M.26 to 25% for ‘Cornice’ on M.7 with the ‘Winter Banana’ interstem. Incompatability suppressed mainly foliar N and Zn but, to a degree, also P, Ca, and B.

Open access

M. N. Westwood, A. N. Roberts, and H. O. Bjornstad

Abstract

‘Golden Delicious’ and ‘Starking Delicious’ apple (Malus domestica Borkh.) on Mailing 9 (M 9) rootstock were planted in 1956 in alternate rows 4.57 m (15 ft) apart, with in-row spacings of 1.22, 1.83 and 2.44 m (4, 6, and 8 ft). Average annual yield was higher at the closest spacing (1794 trees/ha) during the entire 18 years of the test. The pattern of yield was similar for the 2 cultivars but was higher for ‘Golden Delicious’ because of the lower fruit set of ‘Starking’ in some years due to adverse weather. Pruning during the last 6 years of the test was done by mechanical shearing of tops and sides, with no detailed pruning within the fruiting wall. This type of pruning on dwarf trees resulted in adequate fruit size, color, and quality with normal fruit thinning practices.

Open access

M. N. Westwood, A. N. Roberts, and H. O. Bjornstad

Abstract

Growth and yield of ‘Montmorency’ cherry varied greatly both within and between species of rootstock clones. Trees on FI2/1 mazzard (Prunus avium L.) were very vigorous and less productive than those on other stocks. Some growth control was found within each species or hybrid group but was most pronounced with P. mahaleb L. clones PI 193688, PI 163091 and PI 193693. Yield efficiency was not necessarily related to tree size but tended to be better with smaller trees. The 3 P. mahaleb clones listed above and the vigorous clones OCR-3 (P. mahaleb × P. avium) and PI 194098 (P. mahaleb) had high yield efficiencies. Trees on F12/1 and P. mahaleb PI 193703 had the lowest yield efficiencies. Based upon ideal orchard spacing for tree size, calculated annual yields exceeded 10 metric tons per ha for 6 of the clonal stocks.

Open access

M. N. Westwood, P. B. Lombard, Scott Robbins, and H. O. Bjornstad

Abstract

Tree size and performance were summarized for five-year-old apple trees, with a range of vigor, in several cultivars on several size-controlling rootstocks. Trunk cross-sectional area (TCSA) of trees on EMLA 9 was 86% greater than those on M 9, while trees on EMLA 27 had a 48% smaller TCSA than M 9. The percentage of flowering was greatest on trees on M 9 compared to EMLA 9 and 27; greatest on Clark (C) 54 compared to C 6 and C 43; and least on seedling compared to MM 111, MM 106, and M 7. Trees on EMLA 9 and M 9 had high-yield efficiency (cumulative yield/TCSA), whereas those on EMLA 27 were less yield-efficient. Trees on seedling stock were less efficient than those on MM 111, MM 106, and M 7. Smallest trees based on TCSA were noted for both ‘Oregon Spur Delicious’/EMLA 27 and ‘Starkrimson’/C 54, whereas the largest trees were ‘Starking Delicious’/Merton 793.