Effect of Date of Pruning, Timing, Number and Composition of Oil Emulsion Sprays on Harvest Pruned Sultana

Abstract

During four seasons of harvest pruning from 1972 to 1975 Sultana canes were cut in early, mid or late March. The bunches were sprayed either once (on the same day, or three days later) or twice (on the day of pruning and again four days later, or three and seven days after pruning) with 0.7, 1.2, or 1.7% potassium carbonate oil-in-water emulsion (oil spray).

Rate of fruit drying was increased by: pruning in early instead of mid or late March, using two instead of one oil spray, using 1.7% potassium carbonate instead of 1.2 or 0.7% in the oil sprays, and applying the first spray on the day of pruning instead of three days later.

There was no consistent effect of date of pruning on fruit grade, yield or vine growth. The early March pruning produced light type fruit (unless rain occurred) and the mid and late March prunings had brown type fruit.

There were no consistent differences in fruit grade and yield between one or two oil sprays, 1.7, 1.2 or 0.7% potassium carbonate, and first oil spray applied on the same day as pruning or three days later.

Harvest pruning produced fruit that was almost free of grit.