Articles
Alternate bearing in olive – mitigation with properly timed foliar-applied naphthaleneacetic acid or pruning
Article number
1446_21
Pages
149 – 158
Language
English
Abstract
Climate events causing floral bud abortion, poor pollination or abscission of reproductive structures result in alternate bearing (AB) in olive (Olea europaea L.). Alternating low-yield years (OFF crops) following high-yield years (ON crops) have negative economic impacts on orchard management, harvesting, marketing, production of value-added products, and consumer prices, which destabilize the sustainability of olive commodity-based industries.
In this research, AB severity for ‘Manzanillo’ olive, based on alternate bearing index (ABI), where 0 equals no AB and 1 is complete AB (crop one year, no crop the next), ranged from 0.35 to 0.94. Non-bearing shoots (NBS) on OFF-crop trees produced 20-fold more inflorescences the following spring than bearing shoots (BS) of ON-crop trees, whereas NBS on ON-crop trees produced 15-fold more inflorescences than BS. To increase flowering and yield following an ON-crop year, the number of NBS needs to be increased.
Flower removal at full bloom (FB) with naphthaleneacetic acid (NAA) or fruit removal 28 days after full bloom (DAFB) by pruning were imposed on one side of commercial ‘Manzanillo’ olive trees and then the other side annually versus every other year (biennially). Over a 4-year period starting with an ON crop, for untreated ON-/OFF-crop control trees, ABI for total yield was 0.94 and ABI for yield of commercially valuable medium plus large (M+L) size fruit was 0.80. Foliar-applied NAA at FB or pruning 28 DAFB to one side of the tree annually reduced the ABI for total yield to 0.75 and 0.72, respectively, and ABI for yield of M+L size fruit to 0.70 and 0.61, respectively.
In contrast, foliar-applied NAA at FB or pruning 28 DAFB to one side of the tree biennially reduced the ABI for total yield to 0.58 and 0.47, respectively, and ABI for yield of M+L size fruit to 0.46 and 0.37, respectively.
There were no differences in 4-year cumulative total yields among treatments, whereas cumulative yields of M+L size fruit were 20 and 40% greater for trees treated with NAA or pruned biennially than trees treated annually for the same 3-year period (P<0.01).
In this research, AB severity for ‘Manzanillo’ olive, based on alternate bearing index (ABI), where 0 equals no AB and 1 is complete AB (crop one year, no crop the next), ranged from 0.35 to 0.94. Non-bearing shoots (NBS) on OFF-crop trees produced 20-fold more inflorescences the following spring than bearing shoots (BS) of ON-crop trees, whereas NBS on ON-crop trees produced 15-fold more inflorescences than BS. To increase flowering and yield following an ON-crop year, the number of NBS needs to be increased.
Flower removal at full bloom (FB) with naphthaleneacetic acid (NAA) or fruit removal 28 days after full bloom (DAFB) by pruning were imposed on one side of commercial ‘Manzanillo’ olive trees and then the other side annually versus every other year (biennially). Over a 4-year period starting with an ON crop, for untreated ON-/OFF-crop control trees, ABI for total yield was 0.94 and ABI for yield of commercially valuable medium plus large (M+L) size fruit was 0.80. Foliar-applied NAA at FB or pruning 28 DAFB to one side of the tree annually reduced the ABI for total yield to 0.75 and 0.72, respectively, and ABI for yield of M+L size fruit to 0.70 and 0.61, respectively.
In contrast, foliar-applied NAA at FB or pruning 28 DAFB to one side of the tree biennially reduced the ABI for total yield to 0.58 and 0.47, respectively, and ABI for yield of M+L size fruit to 0.46 and 0.37, respectively.
There were no differences in 4-year cumulative total yields among treatments, whereas cumulative yields of M+L size fruit were 20 and 40% greater for trees treated with NAA or pruned biennially than trees treated annually for the same 3-year period (P<0.01).
Publication
Authors
E.J. Fichtner, C.J. Lovatt
Keywords
alternate bearing index, climate, commercially valuable size fruit, flower and fruit thinning, OFF-crop trees/years, ON-crop trees/years, total yield
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