Improving Fruit Quality
Preventing Apple Fruit Russet
Fruit russet is a particularly common problem in Golden Delicious. It is typically caused by the presence of water on the fruit surface during the first 45 days of fruit development. High relative humidity, dew or rain, light frosts, and reaction to some pesticides may also cause russeting. Multiple applications of gibberellic acid (GA4+7) during the 45-day period after bloom has been shown to reduce fruit russeting. See table below.
Using GA4+7 (ProVide, NovaGibb) to Prevent Apple Fruit Russet
| Rate of ProVide | Timing | Notes |
|---|---|---|
| 10-13 oz/100 gal | Start at late bloom or petal fall Repeat every 7-10 days for a total of 4 applications |
Do not exceed 40 oz/acre in one season Can be mixed with pesticides Cannot be mixed with nutrient sprays or spreader-stickers Do not apply through irrigation |
Improving Fruit Shape
A combination of benzyladenine (BA) and gibberellic acid (GA4+7) is sold as Promalin or Perlan and can be used to increase fruit size and “typiness” (fruit length) of lobed apple varieties such as Delicious. Reports from Michigan and other eastern regions have shown a negative interaction between Promalin application and subsequent NAA thinning applications. However, this has not been as big of a problem in the West. See table below.
Using BA and GA4+7 Formulations to Improve Apple Fruit Shape
| Rate of Promalin | Timing | Notes |
|---|---|---|
| Single Application | Do not exceed 2 pints per acre in one season. | |
| 1-2 pints/acre | Early king bloom to early petal fall. | |
| Split Applications | ||
| ½-1 pint/acre | Apply first spray at start of king bloom. Apply second spray when remaining side blooms have opened. |
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