Volume 61 Number 2 Article 10 Pages: 61-70
Year 2007 Month 4
Title: Canopy Separation and Defoliation do not Improve the Dry-on-Vine (DOV) Raisin-Making Method for 'Thompson Seedless' Grapevines on Traditional Trellises
Authors: M.W. Fidelibus, S.J. Vasquez and K.A. Cathline
Citation
Abstract:
‘Thompson Seedless’ (syn. ‘Sultana’) grapevines (Vitis vinifera L.) were subjected to canopy separation and
defoliation treatments to determine whether either or both of those factors could increase pruning efficiency, the
number of clusters per vine, canopy evaporative potential, yield, or quality of dry-on-vine (DOV) raisins.
Canopy
separation methods included: 1) within-row alternate bearing (WRAB), where fruiting canes and renewal shoots
were trained to opposite sides of the trunk such that each were adjacent to similar structures of neighboring vines,
2) Wave, where fruiting and renewal canes were trained to opposite sides of the trunk such that the fruiting canes
of one vine were adjacent to the renewal shoots of the next vine, or 3) non-separated.
Defoliation treatments,
applied near cane severance, included burning or blowing the leaves, application of concentrated solutions of
calcium ammonium nitrate (CAN-17), urea ammonium nitrate (UAN-28), or ethephon (750 ppm) to leaves, or no
defoliation.
None of the canopy separation or defoliation treatments provided any consistent benefit with respect
to the variables measured.
On the contrary, vines with separated canopies sometimes had more congested fruiting
zones, as evidenced by their greater number of cluster layers, than vines with non-separated canopies, and their
raisins were often moister at harvest.
In one trial, defoliation by blowing or burning enhanced drying of raisins on
vines whose canopies were subjected to the WRAB method, but in another trial the use of those defoliation methods
resulted in raisins that were too moldy to process.
Thus these canopy management methods did not improve
the DOV raisin-making method for ‘Thompson Seedless’.
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