R. R. Williams

The effects of paclobutrazol and daminozide on the growth and yield of cider apple trees

SummaryThe effects of soil applications (1, 2 or 4 kg a.i. ha-1 to give 0.25, 0.5 or 1.0 g a.i. per tree) or foliar sprays (1000 or 2000 mg l-1 to give 2 or 4 g a.i. per tree) of paclobutrazol (PP 333) were compared with those of foliar daminozide (Alar) sprays (2000 mg l-1 to give 4 g a.i. per tree) on bush cider apple cv Michelin for two years. Extension shoot growth was significantly reduced in the year of application (Year 1) by foliar paclobutrazol and daminozide sprays, and in the following year by the foliar and high-rate soil-applied paclobutrazol but not by daminozide. Foliar applications of paclobutrazol reduced leaf size and darkened leaf colour, delayed flowering and enhanced fruit set. Yields were not affected by any treatment.

Pseudocompatibility After Self-Pollination of the Apple Cox’s Orange Pippin

SummaryExperiments with flowers of Cox’s Orange Pippin apples have shown that semi- compatible pollen tubes produced by self-pollination may effect fertilization and therefore fruit set. Pseudocompatibility was maximized by pollinating old flowers with large quantities of pollen, and maintaining a temperature of about 20°C during the period of pollen tube growth. The evidence suggests that, with some or all of the above conditions, fertile flowers are able to set fruit with self-pollination.

The Toxicity to Apple Pollen of Several Fungicides, as Demonstrated by in Vivo and in Vitro Techniques

SummaryCommercial fungicides containing dinocap, captan, binapacryl and dithianon reduced pollen germination on stigmas sprayed two hours after pollination, but did not prevent fruit set. Spraying with thiophanate-methyl or benomyl formulations, or spraying any of the fungicides one day before or after pollination, had no effect on pollen germination. The relative toxicity to pollen of these materials was confirmed with in vitro tests, which also included several other fungicides.

Changes in fruit set, leaf size and shoot growth of apple caused by some fungicides, insecticides and a plant growth regulator

SummaryOf seven chemicals sprayed onto apple flowers before flowering or at petal-fall stage one fungicide (triadimefon) increased fruit set, and one insecticide (chlorpyriphos) and the growth regulator (paclobutrazol) decreased it. These three chemicals sprayed at green-cluster stage also reduced eventual leaf size. Later sprays of chlorphyriphos and paclobutrazol sometimes reduced, and gamma-HCH sometimes increased, bourse shoot growth.

Pollen application by mechanical dusting in English Apple Orchards

SummaryApple pollen from cvs Miller’s Seedling or Reine des Reinettes, diluted with pine pollen or with Polyvinylchloride granules, was applied with an experimental pollen duster to Cox’s Orange Pippin trees in 1971, 1972 and 1973, at rates varying from 40 to 800 g ha-1 of pollen. In 1971, when weather conditions at flowering time were good, mechanical application of pollen increased fruit set in orchards with a good cropping history, but failed to do so in orchards with a poor cropping history, presumably because factors other than pollination were limiting fruit set. In 1972 and 1973, when the weather at flowering time was cold and wet, pollen dusting did not result in significant increases in fruit set.

The Effect of Killed Compatible Pollen on Self-Compatibility in Apple

SummaryThe extension of the recognition pollen principle to the gametophytic incompatibility system of the apple Crawley Beauty could not be demonstrated despite reported success with the apple Mcintosh.

Comparison of flower numbers and pollen production of several dessert apple and ornamental Malus cultivars

SummaryThe numbers of flowers, and the amount and viability of pollen they released, were recorded on six dessert apple and five ornamental Malus cultivars over several years. M. χ purpurea cv Aldenhamensis produced as much, and M. cv Hillieri, M. cv Golden Hornet and M. cv Winter Gold far more, live pollen per length of branch, per tree or per canopy volume than most of the dessert cultivars studied.

The effect of picking date on blossoming and fruit set in the following year for the apple cv. Bramley's Seedling.

SummaryBramley’s Seedling apple trees were picked on four different dates in 1978 (23 August, 16 September, 4 and 26 October). Fruit weight almost doubled between the first and the last pickings. Blossom cluster counts in the following year indicated a significant effect of picking date on flower production, with a strong trend for more flower clusters after early picking. There was a highly significant decrease in final fruit set in 1979 relative to first to last picking dates in 1978. The possible effect of early picking and subsequent warm weather on assimilate reserves, and the role of such reserves in stimulating flowering and fruiting are discussed.

Comparison of the compatibility and metaxenia effects of several dessert apple and ornamental Malus cultivars with Cox’s orange pippin

SummaryFlowers of apple cv Cox’s Orange Pippin were hand-pollinated with diluted or undiluted pollen of six dessert and five ornamental Malus cultivars. Subsequent examinations of pollen tube growth, fruit set and seed numbers showed that all were compatible with Cox, though some differences were found. Pollen of four of the five ornamental Malus cvs, viz. Golden Hornet, Hillieri, Winter Gold and Aldenhamensis, was as compatible with Cox as that of the dessert cultivars. No metaxenia effects on size, weight, colour, russet, acidity or sugar content were seen in the pollinated Cox fruit.

The mechanism of yield suppression by a triadimefon fungicide programme on the apple cv Cox’s Orange Pippin

SummaryBlossom characteristics and fruit-set of the apple cv Cox’s Orange Pippin have been examined following spraying for four years with the fungicide triadimefon/bitertanol an ergosterol biosynthesis inhibitor (EBI). The EBI-treated trees did not give the usual mature tree response of increased flower production to a light crop in the previous season. Relative to a standard binapacryl spray flower bud development was delayed and both initial and final fruit-set were reduced by the EBI treatment. The flowers showed no differences in pollen tube growth but ovule longevity was reduced in the EBI flowers. The latter also tended to have smaller ovaries, indicating a possible limitation to fruit size.