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  • Author or Editor: M. N. Westwood x
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Abstract

Recently, Stephen (1) found that pear pollen was carried at least ¾ mile by wind. He was able to collect appreciable amounts of such pollen on glycerine-treated slides placed at various heights and distances from pear trees. Fully seeded Anjou pears were found scattered throughout solid-block plantings, particularly in the border rows and in the tops of trees. Some of the data were difficult to explain on the basis of known bee-flight patterns, inasmuch as the varieties tested are self-sterile.

Open Access

Abstract

Controlled freezing tests showed no hardiness differences between comparable floral developmental stages on weak and vigorous ‘Bartlett’ (Pyrus communis L.) pear trees. Bloom delay through evaporative cooling resulted in a loss of hardiness beyond that found earlier in the season on non-misted trees for similar stages of development, although a certain degree of frost protection was gained through bloom delay.

Open Access

Abstract

Simulated frost injury to ovaries at intervals after full bloom significantly increased fruit malformation, reduced fruit weight, and increased fruit drop in ‘Bartlett’, ‘Bosc’, and ‘Comice’ pear (Pyrus communis L.). Time of injury did not affect fruit weight and malformation in most cases, but did significantly affect fruit drop. Significant positive correlations were found between fruit weight and seed content, while negative correlations were found between fruit malformation and seed content for all cultivars.

Open Access

Abstract

Decline- and fire blight-resistant clonal rootstock selections of Old Home × Farmingdale (OH×F), Pyrus communis L. were compared during a 12-year period with Bartlett seedling, P. calleryana Decne. seedling and clonal Old Home as understocks for ‘Bartlett’. Some OH×F clones were found to be more vigorous than Old Home rootstock, while others were much less vigorous. Only OH×F 51 was as dwarfing as East Mailing (EM) Quince A. Trees on some clones of each vigor class were more efficient (yield per unit of tree size) than others of the same class. Yield efficiency was not well correlated with rootstock vigor, but the semi-dwarf clones tended to induce more efficient yield than vigorous ones.

Open Access

Abstract

Potted seedlings and cuttings of various tree species were submerged to 5–10 cm above the soil level for up to 20 months in order to determine flood tolerance based on leaf conductance (kl), growth, and survival. Flooding induced a decline in kl at soil oxygen diffusion rates of 30, 22, 20, and 15 × 10−8g cm−2 min−1 for Prunus persica (L.) Batsch, Halford seedlings (peach), Pyrus communis L. cv. Bartlett (Bart), Pyrus calleryana Decne (Call), and Pyrus betulaefolia Bunge (Bet), respectively. The leaves of some species, particularly Pyrus communis L. cv. Old Home × Farmingdale 97 (OH × F 97), abscised shortly after a decline in kl, yet leaves of most other Pyrus species did not abscise despite months of maintaining a kl near zero. Growth rates were reduced for all fruit tree species except Bet and Call after one month of spring flooding. One month of fall flooding reduced the growth of all fruit tree species the following spring. Bet survived 20 months of continuous submergence; however, only Salix discolor Muhl. (willow) grew well under these conditions. Flooding promoted adventitious rooting of willow, Cydonia oblonga Mill. cv. Provence BA 29 (quince) and Malus domestica Borkh. cv. MM 106 (apple); anthocyanin pigmentation in leaves of apple and all Pyrus species; leaf chlorosis of quince, apple, and peach; and hypertrophied lenticels on the submerged stems and roots of all species. The tolerance, based upon kl, growth, and survival, was: willow > Bet > Call = quince > Bart > OH × F 97 = Pyrus pyrifolia (Burm.) Nak. (Pyri) = Pyrus ussuriensis Maxim. (Ussuri) = apple > peach. Although the survival of pear rootstocks with and without a ‘Bartlett’ scion were similar, flooding symptoms often were quite different.

Open Access

Abstract

Field and laboratory studies of host preference and resistance of Pyrus species and cultivars to the pear psylla, Psylla pyricola, were conducted in Southern Oregon from 1964–1968. Asian species were generally less attractive to oviposition than those from Asia Minor, North Africa or Europe. Attractiveness of P. pyrifolia and P. communis cultivars was higher than for P. ussuriensis.

Susceptibility of Pyrus was based on differences between total egg deposition and resulting nymphal populations. Using this nymph/egg ratio the results indicated that Asian material was more resistant than material from Asia Minor or Europe. The Asian species P. fauriei and P. calleryana exhibited both a high degree of unattractiveness to oviposition and resistance to nymphal development.

Open Access

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.

Open Access

Abstract

Freezing studies on ‘Bartlett’ pear (Pyrus communis L.) bouquets of buds, flowers, and small fruit showed injury increased with decreasing temperature, increasing developmental stage, and increasing duration of frost. At the minimum temperature, 30 and 60 minutes of frost exposure in all stages increased injury, however, in the small fruit stage injury at −2°C increased for up to 2 hours exposure. The effect of freezing rate was dependent on minimum temperature and dry florets were injured slightly more than florets misted just prior to freezing.

Open Access

Abstract

Pear plots established in 1923 and 1926 with trees composed of several rootstock and trunk combinations were assessed for tree size, susceptibility to pear decline and for fruit quality. In general, Pyrus ussuriensis Max. and P. pyrifolia Burm. & Nak. rootstocks resulted in small trees, P. communis L. and P. calleryana Decne. intermediate, and P. betulaefolia Bunge large. The latter was most resistant to decline, followed by P. calleryana and P. communis, with P. pyrifolia and P. ussuriensis susceptible. The use of the oriental hybrid cvs. Variolosa and Tolstoy as interstocks increased the severity of pear decline symptoms though all trees were not uniformly susceptible. The use of the P. communis cv. Old Home as a scion rooted trunkstock decreased the degree of decline. Fruit quality was good on most combinations but was generally better on P. calleryana than other rootstocks. Pyrus betulaefolia caused cork spot and poor quality of ‘Anjou’ but this same rootstock resulted in outstanding quality of ‘Seckel’.

Open Access

Abstract

A pre- or postharvest foliar B application was found to increase fruit set of ‘Italian’ prune (Prunus domestica L.). A prebloom B spray failed to increase set. Neither fall nor spring applications influenced the amount of fruit lost in the midsummer or “blue” drop. All trees involved in the experiment had adequate B by the standard index of tree nutrition, August mid-shoot leaf analysis. Incipient B deficiency did not appear to be involved.

Fall foliar B increased B levels in dormant bud and spur tissues and in flower buds and flowers. A prebloom B spray increased B levels of floral tissues to a lesser degree. The highest B concentration was found in the ovary. Boron concentration in flower buds in April following a fall B spray was as much as five times the amount found in mid-shoot leaves in August. August mid-shoot leaf analysis revealed higher levels in leaves from trees treated the previous fall in only one of the 2 years.

Several morphological and physiological effects of the fall B spray were observed. Among these were a slight delay in the time of bud break, a decrease in the size of flower buds and mature flowers accompanied by reduction of style and pedicel length, and a decrease in pollen germinability. B level of pistil and pollen had no effect on in vivo pollen tube growth rate.

Open Access