Foliar Calcium Corrects a Deficiency Causing Green Fruit Drop in ‘Draper’ Highbush Blueberry (Vaccinium corymbosum L.)

Abstract

‘Draper’ northern highbush blueberry (Vaccinium corymbosum L.) is a widely-planted mid-season cultivar with excellent fruit quality. Under the climatic conditions of Southwestern British Columbia, Canada, and Northwestern Washington, USA, it expresses a physiological disorder causing spontaneous green fruit drop (GFD) of up to half of the developing crop just prior to onset of the fruit coloring phenophase. Reduction of economic losses due to GFD required identification of the cause of this disorder and development of an agronomic solution that would reduce fruit drop. In 2014, two initial experiments were conducted to compare three foliar Ca products under a range of N fertilization rates. In 2015 and 2016, three locations were used in a first step to optimizing rates and timings of foliar Ca application. Initial experiments determined that higher N fertilization rates exacerbate GFD but that foliar Ca corrects the condition. Multi-site, multi-year trials identified key rates and timings for foliar Ca application to provide an agronomic solution for commercial growers. These trials identified an acute fruit Ca deficiency as the cause of GFD, and that foliar calcium applied frequently at high concentration from mid-bloom onward can be effective in reducing GFD, often to negligible levels. This condition has now been reported in several production regions around the world.

High-quality reference genome and annotation aids understanding of berry development for evergreen blueberry (Vaccinium darrowii)

“…6 ). Calcium is important for fruit size and prevents blueberry fruit drop during the early stages of fruit development 29 . Calcium uptake in berries was found to accelerate in the early green stage, then reduce during the coloring stage and cease completely in the ripening stage 30 .…”

Evaluation of Foliar Application of Different Types of Nanofertilizers on Growth, Yield and Quality Parameters and Nutrient Concentration of Cotton under Irrigated Condition

“…Moreover, calcium can only moves up into the plant through water stream in xylem and it is associated with transpiration process (Gerbrandt et al, 2019) and does not perform phloem transport (Etienne et al, 2018). Calcium transport from the site of application to adjacent leaf through foliar is possible but further translocation or redistribution to another plant organ will not takes place due to it"s immobility nature (Bukovac and Wittwer, 1957).…”

Wild Blueberry Fruit Drop: A Consequence of Seed Set?

“…For instance, Milić et al [15] referred to the plant growth regulator, α-naphthaleneacetic acid, as having a "thinning effect" on fruit as a response to increased berry size as a result of applications during highbush blueberry petal fall. Foliar applications of calcium have been shown to reduce fruit drop in the highbush blueberry cultivar "Draper", which is characterized by a physiological calcium deficiency disorder that causes premature fruit drop [16], suggesting that nutrient deficiency can be one cause of fruit drop. With rabbiteye blueberry, it has been found that applications of aminoethoxyvinylglycine (AVG), an inhibitor of ethylene synthesis, reduce fruit drop in the field [17].…”