100 



O 



Q 



LU 

 > 



< 



O 



3 4 5 6 7 8 



WEEKS AFTER RETAIN APPLICATION 



Figure 1. Cumulative drop of Marshall Mcintosh apples treated with Re Tain, ReTain with either Silwet or 

 Kinetic organosilicate surfactants, and NAA. 



surfactants should be used to enliance uptake and improve 

 the performance of ReTain. The purpose of this 

 communication is to confirm the importance of including a 

 recommended surfactant when ReTain is applied as a 

 preharvest-drop-control compound. Since NAA is the only 

 other compound registered to control drop on apples, it was 

 included to allow comparison with ReTain. 



Materials & Methods 



A block of mature Marshall Mclntosli/Mark was 

 selected at the University of Massachusetts Horticultural 

 Research Center in Belchertown, MA. Sixty trees were 

 blocked into six groups (replications) of 12 trees each based 

 upon crop load and proximity. Trees in each replication 

 were paired, with one tree in each pair being designated as a 

 sample tree while the second tree was designated as a drop 

 tree. On August 15, two trees in each block were sprayed 

 with 90 ppm ReTain only, ReTain with 0.1% Silwet, or 

 ReTain with 0.1% Kinetic, respectively, at a dilute 

 gallonage of 1 25 gallons per acre. One pair of trees in each 



block received a 1 ppm spray of NAA on September 5, and 

 the last pair of trees in each replication received no spray and 

 served as a control. Twenty five fruit were harvested from 

 the perimeter of each sample on September 11, 18, 25, and 

 October 2. The percent of the surface with red color was 

 estimated to the nearest 10% as well as determining if the red 

 color was intense enough to meet US Extra Fancy red color 

 standards. A subsample of 10 fruit , representative of the 

 sample was selected and flesh firmness determined on two 

 sides of each fruit using an Effegi penetrometer. Fruit 

 soluble solids were determined on a composite sample of 

 juice collected while doing the flesh firmness, using a hand 

 refractometer. Fruit from the firmness test were cut in half 

 dipped in a starch-iodine solution, and the starch pattern 

 then rated using the Cornell generic starch chart. On August 

 29, all fruit were picked up under drop-designated trees and 

 discarded. Twice weekly all fruit under drop trees were 

 picked up and counted. On October 20, all fruit remaining 

 on the drop trees were harvested and counted and the 

 cumulative drop calculated. 



Fruit Notes, Volume 65, 2000 



55 



