***** PART III *****
GROWTH REGULATOR, THINNING, CALCIUM
AND POSTHARVEST TREATMENTS
FRUIT ELONGATION FOR DELICIOUS
Promalin has been used to increase the length of Delicious apples. However, the results are not consistent. Sometimes fruit from Promalin-treated trees are similar to those from untreated trees; in other situations, Promalin causes significant fruit elongation. Furthermore, this growth regulator has fruit thinning capabilities.
For growers planning to use Promalin, here are some guidelines. Restricted entry interval 12 hours.
• Calibrate your sprayer. Thinning due to Promalin has often been traced to over application because of improper sprayer calibration and nozzle adjustment. The margin of error with Promalin is not great. The label suggests that Promalin should be applied in 100-200 gals./acre. Therefore, an error in application of 50 gals./acre can result in a 50% increase in the amount of Promalin applied.
• Apply Promalin at 1 pint/100 gals. finished tankmix. (Do not apply more than 1.5 pints per acre).
• Do not apply Promalin when the temperature exceeds 85oF. Excessively warm temperature may increase the thinning response without a corresponding increase in the shape response.
• Do not apply Promalin on young trees. A good rule-of-thumb is not to apply this growth regulator on any tree until it is bearing heavily enough to consider chemical thinning.
• Apply Promalin as soon as weather permits after opening of the king blossom.
• The addition of surfactant or spreader sticker increases both the fruit shape and thinning response to Promalin.
• Leave a few untreated and representative trees in the Promalin-treated block. Initial fruit set, subsequent drop and fruit shape are not constant from year to year. Therefore, the only way to accurately assess the performance of Promalin in your orchard is to leave a few untreated trees in the same block to indicate what would have happened without the Promalin spray.
• Do not apply Promalin and NAA to Delicious in the same year as pygmy fruits may develop.