Abstract

Aim: The aim of this study was to evaluate the contribution of macadamia insect flower visitors on nut set, retention, nut-in-shell and kernel yields.

Materials and Methods: This study was conducted at Macadamia Research Centre, in Kandara, Murang’a for three seasons from August 2020 to May 2022. Nut set and nut retention was assessed by purposively selecting twelve trees that were in full bloom at the study orchard. On each of the twelve trees, racemes at bud stage were randomly selected and labeled on four branches of the same size, at a height of 1 to 1.5 metres from the ground.Racemes were then bagged during the day with mesh nets, others bagged at night and some bagged throughout the flowering season excluding all insects, while some racemes were left unbagged, thus having unlimited flower visitation by insects.

Results: There were significant differences on nut-in-shell yield (mass) (P≤0.05) in flowers that were unbagged (68.23 ± 4.03), bagged during the day (61.50 ± 3.51), bagged at night (6.53 ± 1.05) and those that were bagged throughout (4.45 ± 0.95). Racemes that had flower visitors fully excluded,resulted in low nut-in-shell production.The initial nut set, retention and ultimately the nut-in-shell yields were significantly increased in flowers that were left unbagged thus insects had unlimited access.

Conclusion: It was concluded that Macadamia nut set, retention and ultimate yield is highly reliant on pollen transfer which is mediated by insect flower visitors that forage during day time.

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