Pollination of Hass Avocados

Botanical horticultural and entomological aspects were studied in an attempt to compare the influence of cross-pollination (Hass x Ettinger) and self-pollination (Hass x Hass) as well as the role of bees on Hass yield. The experiments were carried out in two 5 year old Hass orchards bordered by rows of Ettinger trees at Mooketsi and Politsi. Semi-in vivo pollination experiments confirmed that Ettinger, but also Fuerte and Bacon, are effective pollen parents for Hass and slightly out-performed Hass. In an experiment where open-pollinated Hass flowers were sampled over a two- week period, it was found that weather conditions, especially low temperatures before and after female phase anthesis, gave an adverse effect on 'effective pollination'. In night time counts in the Mooketsi orchard, powder-marked bees had visited up to 10 inflorescences out of 10 per tree sampled close to the hives, with a gradual decline to 2 at 200m distance from the hives. Day time counts of the number of foraging bees per 1m 2 of flowering canopy (or per 20 inflorescences) were 4 near the hives (5 being considered optimal), declining to 1 at 200m distance. The six hived colonies showed an initial increase in size, brood, honey and pollen, whereafter brood and pollen production declined. In the Politsi orchard only the inflorescences very close to the hives were powdermarked (highest count 4/10). Day time counts also revealed no bees on trees within 200m from the hives, but a high 5 bees/20 inflorescences in a far corner of the orchard, 550m from the hives. Competitive beeplants such as weeds, surrounding bush and eucalypts were possibly responsible for the absence of bees in the orchard. The 8 hived colonies, two of which also prepared to swarm, showed a gradual increase in all the measured parameters, except for a slight decline in the brood production towards the end of flowering. Hass yields of caged trees with bees were significantly higher than those without bees. One open-pollinated block showed a decline in Hass yield with increasing distance from Ettinger pollen donor. However, in another block Hass yield was not influenced by distance from Ettinger.