Rabbiteye blueberry (Vaccinium virgatum) bushes can live for many years, but if they are not well maintained they can lose vigor and fruiting productivity (Stafne et al., 2020). Renovation pruning is a way to re-invigorate bushes by severely cutting back old growth to promote flushes of new canes that lead to more fruit-bearing potential. Producers who purchase old rabbiteye blueberry plantings often have questions on how best to rejuvenate bushes, including how much to cut off and when fruit will be harvested again. In much of the southeastern United States, mature bushes are sheared or topped immediately after harvest each year, which allows sufficient time for cane regrowth and fruiting bud development during the remaining summer period. While this is a common practice on rabbiteye blueberry bushes, a more radical pruning (renovation) is sometimes required to re-invigorate moribund and poorly maintained plantings of highbush blueberry [Vaccinium corymbosum (Longstroth, 2015)] and rabbiteye blueberry (Austin and Brightwell, 1984). When renovation pruning is performed, blueberry bushes are pruned to the ground or close to the ground, resulting in no fruit production the following year or perhaps even longer. However, if plants recover quicker, then an earlier harvestable crop could be gained to offset the costs of the renovation process.
Phosphorous acid, or phosphite, is a reduced form of phosphate and is often marketed as a fungicide that may also have other plant health-inducing or biostimulant properties. Phosphite has been reported to reduce plant stress and thereby indirectly improve yields and fruit quality. Woody fruit crops, such as avocado (Persea americana) and citrus (Citrus sp.) (Lovatt, 1999, 2013) and peach (Prunus persica) and red raspberry (Rubus idaeus) (Rickard, 2000), have been studied; however, there are conflicting reports on why phosphite application may be effective in improving plant productivity (Gomez-Merino and Trejo-Tellez, 2015; Thao and Yamakawa, 2009). The potential of this type of application in rabbiteye blueberry has not been explored as it has in other crops.
The purpose of this study was to determine how renovation pruning height affects rabbiteye blueberry plant growth, fruit quality, and total yield in the second and third growing seasons after treatment and combined across first-year phosphite applications.
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