Sprays for Setting Currants	AG1198
Rosie Hannah, Mildura November 2004

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Zante currants

The uneven development of berries on mature bunches is a greater problem than berry setting on Zante currants.

The best way to ensure the development of even sized berries is to spray the vines with the growth retardant (use a chlormequat formulation registered for this use on grapevines) at 100ppm and a growth regulator, gibberellic acid (GA) at 1ppm at full bloom.

Spray the vines to the point of run-off, making sure that all bunches, are thoroughly wetted. Thorough coverage is most important with chlormequat applications.

Research by the Department of Primary Industries (DPI), suggests that a split application of 100ppm chlormequat and 1ppm GA may give better results than the standard combined setting spray, particularly with excessively vigorous vines.

When using the two chemicals separately, the chlormequat is applied seven days after bunch droop (about two weeks prior to flowering) and the GA is applied at full bloom.

Carina currants

Carina is sensitive to weather at flowering and in some years the caps will not fall freely from the flowers. Carinas require a setting spray to produce satisfactory crops and uniform berry size.

Research has indicated that applying between 100 and 300ppm of chlormequat seven days after bunch droop (about two weeks prior to flowering) and 1ppm GA at 80-100% capfall will often give better results than the standard currant setting spray (according to the GA label). The higher concentrations of chlormequat should be used on more vigorous vines.

Timing of the sprays

Timing is important. Because the stage of growth will vary from one property to another it is necessary to assess the stage of flowering on your own property. A good way of doing this is to select and mark 20 vines at random throughout the currant patch; inspect them daily before and during the flowering period.

Bunch droop
Bunch droop is the stage of growth when the bunches fall from the vertical upwards position. It usually occurs between two and three weeks before flowering. Bunch droop is more obvious in Zante than in Carina currants.

Full bloom
Estimate the percentage of capfall on each vine and calculate the average capfall for the 20 vines each day.

When an average of 80-90% of the caps have fallen from bunches the vines are in full bloom stage.

Other factors to observe

Make sure that the soil is moist at the time of spraying.

Don't top vines before spraying. Topping or tipping does not improve development of currant berries.

It is important to apply the spray on its own. It should not be mixed with other agrochemicals.

Important points for spraying

Important points for spraying chlormequat:

• Do not spray during the heat of the day, or if rain is likely within two hours.
• Do not apply to vines likely to suffer stress.
• Do not apply to wet foliage
• Do not apply more than once in a season.

• Use with a non-ionic wetter
• Do not apply to vines under pest, nutritional or water stress.