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Honeybee flora of South Africa: exotic and indigenous plants
Honeybees visit about 1000 plant species in South Africa for pollen and/or nectar. Only half of these plant species are indigenous (Illgner, 2002). Many South African beekeepers migrate with their hives over distances of hundreds of kilometres to certain crops as they flower, and use minor nectar sources to bridge periods between major nectar flows (Johannsmeier, 2001). For example, in the northern summer rainfall area, the cycle begins in spring with certain Eucalyptus species, followed by Faurea saligna (boekenhout) and Fagopyrum esculentum (buckwheat) in December. In January honeybees are used to pollinate Phaseolus coccineus (kidney beans) and Helianthus annuus (sunflowers) and in autumn Cosmos bipinnatus (cosmos) is available. Eucalyptus grandis flowers from April onwards while July and August are the important Aloe months (Keats, 1980). The annual honey crop in South Africa is estimated at 3 500 tons, of which 1 800 tons is derived from Eucalyptus, 900 tons from crop plants and the remainder from weeds, indigenous and other plants (Johannsmeier, 2001). Of the exotic bee plants, the single most important nectar source for bees is Eucalyptus and beekeeping is considered impossible without it. There are 34 Eucalyptus species listed as honey plants in South Africa. These trees are highly attractive nectar and pollen producers, grow under a variety of conditions and have a widespread distribution with a year-round flowering period (Johannsmeier, 2001; Illgner, 2002). In South Africa a timber industry, based on fast growing trees such as pines and eucalypts, was established at the end of the nineteenth century, and by the early twentieth century the majority (80%) of trees grown were Eucalyptus grandis.
These plantations provided additional and more reliable sources of nectar than the indigenous flora. However, since 1975 Eucalyptus nectar flows have declined to about one third of the previous average. Various factors may contribute to this deterioration; Drosophila flavohirta larvae utilising the nectar in Eucalyptus flowers (Herrmann, 1983; Nicolson, 1994) and the leaf sucking bugs Thaumastocoris australicus that cause defoliation, dieback of branches and even death of Eucalyptus trees (Jacobs & Neser, 2005). Thaumastocoris australicus may even affect the flowering and nectar production of infested Eucalyptus trees (D. Jacobs, pers. comm.). Another explanation may be the genetic make up of the trees currently planted in plantations; Eucalyptus with fewer flowers are preferred, thus less nectar is available to honeybees (A. Schehle, pers. comm.). Government regulations (the Working for Water Programme) provide for the removal of certain Eucalyptus species in water catchment areas and along watercourses, and this presents another threat to beekeepers (Johannsmeier, 2001). Of the indigenous plants, the major producers of honey are firstly the aloes, of which A. greatheadii var davyana is the most important species, followed by boekenhout (Faurea saligna), wilde peer (Dombeya rotundifolia), karee (Rhus lancea), wilde sering (Burkea Africana), wit-olyf (Cordia caffra), as well as several Acacia and Protea species (Beyleveld, 1969; Fletcher & Johannsmeier, 1978; Schonfeld, 1983; Johannsmeier, 2001). An extensive list of bee plants in South Africa, including their distribution as well as flowering phenology, has since been compiled by Johannsmeier (2001) and Illgner (2002).
The genus Aloe
The genus Aloe, family Asphodelaceae, occurs across a wide range of habitats, from dry forests to scrublands in Africa, Madagascar, Arabia, the Canary and the Comoro islands. South Africa has the highest diversity of Aloe species with more than 100 species (Van Wyk & Smith, 1996; Glen & Hardy, 2000; Smith et al., 2000). These succulent plants grow well in warm climates and can tolerate drought. Few species, however, can withstand frost. The huge variation in size, leaf width, leaf markings, etc., has led to the division of the genus into 26 sections (Reynolds, 1969; Van Wyk & Smith, 1996; Glen & Hardy, 2000).
The section Pictae (spotted aloes) is the largest, consisting of 32 species. These aloes are stemless or short-stemmed, have inflorescences that are branched and re-branched and their flowers, with conspicuous basal swellings, often have pale longitudinal stripes. Species are difficult to distinguish from each other e.g. the summer flowering Aloe zebrina and winter flowering A. greatheadii var davyana (Schönland) Glen & D.S. Hardy (Van Wyk & Smith, 1996; Glen & Hardy, 2000). Aloe greatheadii var davyana and honeybees, Apis mellifera scutellata The winter flowering A. greatheadii var davyana (Fig. 1) has a widespread distribution across the summer rainfall area (Fig. 2) and is very common in the Bushveld and on the Witwatersrand (Glen & Hardy, 2000; Van Wyk & Smith, 1996; Smith & Crouch, 2001). The plants grow well in rocky terrain and on grassy plains and occurring most densely in overgrazed areas (Clark, 1992). Plants are robust and grow singly or in groups of up to fifteen.
They flower prolifically in mid-winter, from June to August, with flower colour ranging from pale pink to bright red. Flower abundance may vary throughout the flowering period and from year to year. Pronounced daily temperature changes characterise the winter flowering period with warm days and cold, sometimes frosty, nights. Aloe greatheadii var davyana is a major indigenous beeplant and it is widely known that beekeepers move their hives to the aloe fields north of Pretoria in winter (see Fig.3) to make use of the strong nectar and pollen flow from A. greatheadii var davyana (Fletcher & Johannsmeier, 1978). The first report on the utilisation of this aloe was that of Mr Krohn from Rustenburg in 1934 (Williams, 2002). However, it was only in 1950 that Mr E.A Schnetler realised the commercial value of A. greatheadii var davyana. While transporting bees along the Warmbaths (now Bela Bela) road to a new site, his truck broke down and the bees had to be unloaded. When it was time to reload the hives he realised that the bees were collecting pollen and nectar from A. greatheadii var davyana growing in the vicinity (Short, 1962; Keats, 1980).
Table of contents :
- Acknowledgements
- Abstract
- Table of contents
- General Introduction
- References
- Chapter 1: Nutritional content of fresh, bee-collected and stored pollenof Aloe greatheadii var davyana (Asphodelaceae)
- References
- Chapter 2: Influence of Aloe greatheadii var davyana (Asphodelaceae)
- pollen quality on ovarian development in honeybees,
- Apis mellifera scutellata
- References
- Chapter 3: Nectary structure and nectar presentation in Aloe castanea and A. greatheadii var davyana (Asphodelaceae)
- References
- Chapter 4: Dilute nectar of Aloe greatheadii var davyana as a resource for honeybees, Apis mellifera scutellata, during dry South African
- winters
- References
- Chapter 5: Do honeybees, Apis mellifera scutellata, eliminate excess water from the dilute nectar of Aloe greatheadii var davyana before
- returning to the hive?
- References
- Chapter 6: Do honeybees, Apis mellifera scutellata, regulate humidity in their nest?
- References
- Chapter 7: Appearances can be deceiving: insect-pollinated Aloe greatheadii var davyana has an ornithophilous pollination syndrome
- References
- General conclusion
- References
- Appendix: Cytological features of Aloe greatheadii var davyana pollen:
- a comparison between fresh, bee-collected and stored pollen
- References
