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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Production and Genetic Improvement Research Unit » Research » Publications at this Location » Publication #401713
Research Project: Genetic Improvement of Blackberry, Red and Black Raspberry, Blueberry, and Strawberry

Location: Horticultural Crops Production and Genetic Improvement Research Unit

Title: Reduced-input pruning methods are a viable option for machine-harvested 'Mini Blues' highbush blueberry

Author
item STRIK, BERNADINE - Oregon State University
item DAVIS, AMANDA - Oregon State University
item JONES, PATRICK - Oregon State University
item FINN, CHAD - Former ARS Employee

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/17/2022
Publication Date: 10/15/2022
Citation: Strik, B.C., Davis, A.J., Jones, P.A., Finn, C.E. 2022. Reduced-input pruning methods are a viable option for machine-harvested 'Mini Blues' highbush blueberry. HortScience. 57(10):1313–1320. https://doi.org/10.21273/HORTSCI16703-22.
DOI: https://doi.org/10.21273/HORTSCI16703-22

Interpretive Summary: ‘Mini Blues’ highbush blueberry was released in 2016 by the late Dr. Chad Finn as a high-quality, machine-harvestable alternative to lowbush or other small-fruited highbush blueberry cultivars for processed markets. This work examined if lower input pruning methods is effective at maintaining yield and berry quality during the establishment phase of blueberry production. Speed pruning was a successful method and reduced pruning costs by 85% compared with the conventional method of pruning highbush blueberry.

Technical Abstract: Mini Blues’ highbush blueberry (Vaccinium sp.) was released in 2016 as a high-quality, machine-harvestable alternative to lowbush (V. angustifolium Ait.) or other small-fruited highbush blueberry cultivars for processed markets. A planting was established in Oct. 2015 in western Oregon to evaluate the effects of pruning method on yield, machine-harvest ef'ciency (MHE), berry weight and total soluble solids (TSS), leaf tissue nutrients, pruning weight, pruning time, and costs. Plants were pruned for shape and to remove 'ower buds in 2015–16 and 2016–17. Pruning treatments began in 2017–18 and included: 1) conventional highbush pruning (HB); 2) removing one or two of the oldest canes per bush (Speed); 3) leaving plants to grow from 2017 to 2021 (Unpruned) before doing a hard renovation prune in 2021–22 (cutting the plants back to a height of ''0.3 m and leaving the best 8–10 canes/plant); and 4) hedging after fruit harvest in 2018 (Hedge) and then unpruned afterward until renovation in 2021–22. The pattern of yield progression, observed wood aging, and reduced berry size after 4 years of no pruning indicated renovation was necessary in the un-pruned and hedge treatments. Low growth was removed each year in all treatments, and hedging was only done in 2018 because it severely reduced yield the following year and, there-fore, was not a viable option. An over-the-row machine harvester was used from 2018 to 2021. Speed-pruned plants, averaged over 4 years, had the greatest potential yield (3.75 kg/plant) compared with the other treatments (averaged 2.99 kg/plant) but had a similar yield as HB because more fruit remained on the bush after harvest with speed pruning. In 2021, speed pruning resulted in the highest yield (4.2 kg/plant), followed by HB (3.8 kg/plant) and the un-pruned and hedge methods (averaged 3.1 kg/plant). MHE increased from 43% in 2018 to 74% in 2021, mainly because, as the plants aged, a larger proportion of the canopy was above the catcher plates on the harvester. On average, MHE was highest with HB pruning (70%), intermediate in the unpruned and speed-pruned plants (59%), and lowest in the hedged plants (49%). In 2021, ground drop loss was highest for hedge (18%), lowest for speed (14%), and intermediate for HB and unpruned (averaged 16%) methods. HB-pruned plants had heavier berries (0.64 g) than unpruned and hedge treatments (averaged 0.57 g) and a similar berry weight as the speed-pruned plants (0.61 g). Pruning had no effect on berry TSS. In contrast to leaf K, leaf Mg and Ca concentrations were lowest in HB and higher in all other treatments. In 2020–21, HB pruning required 471 h·ha21, while speed pruning took 79 h·ha21; the hedge and unpruned treatments required an average of 60 h·ha21 to remove low-growing branches that would interfere with machine harvest. In 2021–22, renovation of the unpruned and hedge treatments took 290 h·ha21. While leaving bushes unpruned during establishment appears to be a promising option for ‘Mini Blues’, further work is needed to evaluate fruit production after renovation and to determine how long the plants could remain unpruned thereafter. Speed pruning is also a good option, reducing pruning costs by 85%.