Direct assessment of honeybee pollination and the impact of pollinisers

The objective of this project was to determine if polliniser distribution in deciduous fruit orchards, and the distance from polliniser trees, in the Western Cape was resulting in localised depressions in fruit production in orchards, and to assess the extent of this effect in the various polliniser planting patterns utilised in the Cape. This subject was the topic for a MSc for Boipelo Ramogalo in the Department of Zoology at the University of Stellenbosch.

The project was carried out on Lourensford Estates and the impact of polliniser position and planting pattern on fruit set and fruit quality was assessed in three plum orchards, 3 apple orchards and four pear orchards, either in the 2004/2005 season or the 2005/2006 season. These six orchards represented the 2×2 planting patterns, and two versions of the 1-in-9 planting pattern.

Approximately 8 000 clusters of blossom were marked in the orchards, relative to the position of pollinisers, and the fruit harvested from these orchards just prior to normal picking. All these fruit were weighed, and in the case of apples and pears, the number of seeds was counted. An assessment was made for each cultivar, for each orchard, and for each planting system, on the impact of polliniser position on pollination ( = number of seeds), fruit weight and fruit set. The relationships between fruit set and fruit weight, and between fruit weight and the number of seeds in the fruit, were also assessed for all fruit types and cultivars.

In addition to polliniser effect, a range of other factors that might influence fruit set and fruit quality were assessed. These include: the distance from introduced honeybee colonies; position in the orchard; sun effect; orchard effect; and cultivar effect. The relationship between these factors and the possible polliniser effect was also assessed.

These data are presently still be analysed and final results are pending; the MSc will be completed by the send of 2006 and completed results will be available then. The thesis is being prepared as chapters for publication, and it is anticipated that 3 manuscripts ready for submission will be available early in 2007. At present the results appear both interesting and unexpected. Full results are not presented in this report, as it is not possible to precede the MSc. A list of anticipated results is, however, presented in the results/discussion section.

It is recommended that these projects and results, together with all other pollination projects and results, be subject to a careful review in 2007 before future pollination projects are commissioned.