The effect of supplementary pollination on nut set of Macadamia (Proteaceae)

Abstract

The effects of supplementary pollination on initial and final nut set and nut weight of the Macadamia cultivars, 'Hawaii Agricultural Experiment Station 246' and 'Hidden Valley A4', were assessed over 3 years at an orchard in eastern Australia. The final nut sets of racemes bagged to exclude insect pollinators were low in all 3 years of the study for both cultivars. This demonstrated the importance of exposure to insect visitors to increase nut set of these cultivars. However, the improved initial nut set by supplementary cross pollination of 246 in all 3 years of the study showed that insect pollination is inefficient compared to hand pollination. Furthermore, supplementary cross pollination of 246 increased final nut set by 57-97% in 1989 and increased nut weight by 15.0% and kernel weight by 20.0% in 1991. Cross pollination of A4 did not result in any consistent pattern of initial nut set and did not improve final nut set, but increased nut weight by 11.6% and kernel weight by 18.4%, with a higher percentage kernel recovery in 1991. In addition, supplementary self pollination of A4 increased nut sets in both 1989 and 1990. Yield and quality of both cultivars may benefit from increasing pollen transfer in the orchard.