-20- 



Table 1. Effect of the site of Promalin application on the L/D ratio of Richared 

 Delicious apples. 



^50 ppm solution containing 0.05% X-77 applied at fullbloom. All blossom clusters 

 reduced to one flower and then hand-pollinated with Early Mcintosh pollen. 



YA 25 microliter droplet was large enough to wet the receptacle or pedicel surface 

 with no runoff. 



'^Numbers in a column followed by a different letter are significantly different at odds 

 of 19 to 1. 



Petals at the normal application time account for a substantial portion of the flower 

 surface area. However, they appear to be relatively unimportant as a vehicle for 

 absorption. Even 150 pi applied to the petals (the volume comparable to a dilute 

 application) was only moderately effective at increasing the L/D ratios. Spur leaves 

 were totally ineffective as sites of Promalin absorption. Therefore, not only must 

 Promalin be directed uniformly to all parts of the tree but droplets must also come 

 in direct contact with the receptacle of each flower for the maximum response. 



Use of surfactants and adjusting pH of spray solution. Surfactants frequently increase 

 the penetration of growth regulators. However, the use of surfactants is generally 

 not recommended with growth regulators, since most formulated growth regulators 

 (e.g.. Alar 85, Fruitone N, e.tc.) already contain a surfactant. In contrast, the Promalin 

 formulation contains no surfactant, so we thought that the use of a surfactant with 

 Promalin might increase the Promalin effect on fruit L/D ratio. In addition, the ability 

 of gibberellins to enter the plant may be regulated by spray pH. Reduction of the pH 

 of the spray from near neutrality (pH 7.0) down to near pH 4.0 should enhance penetration, 

 but field effects have not been well documented. 



A trial was conducted using a combination of surfactants and a reduction in spray 

 pH was done on Royal Red Delicious. Glyodin, Biofilm and Buffer-X served as surfactants 

 and the pH was reduced in 2 treatments with the nutrient spray Sorba Mg. Buffer-X 

 contains a buffer to reduce pH (pH 4.8 in this trial). The combined sprays of a surfactant 

 with the commercial buffer tended to increase the L/D ratio beyond that produced 

 by Promalin alone (Table 2). Growers must be cautioned, however, that the enhanced 

 response with surfactants and/or buffers also increase the chance of thinning. 



L/D = Length/diameter ratio. An apple with an L/D ratio of 1.04 is longer and more 

 "typey" than one with a ratio of 0.90. 



