Effects of Simulated Rain Following 

 ReTain Application on Preharvest 

 Drop and Fruit Quality of 

 Mcintosh Apples 



Duane W. Greene, James Krupa, and Jon Clements 



Department of Plant and Soil Sciences, University of Massachusetts 



All who manage orchards have experienced the 

 indecision associated with having a weather forecast 

 suggesting the possibility of a 30 to 50% possibility of 

 thundershowers on a day when you would like to spray. It 

 would help the decision-making process to know what the 

 repercussions would be if heavy rain followed the 

 application of a very important spray application. The 

 purpose of this study was to evaluate the effects that a 

 simulated heavy thundershower would have on preharvest 

 drop and fruit quality following a ReTain application. 



Materials & Methods 



1992 Study. A block of 5-year- 

 old Marshall Mclntosh/Mark was 

 selected at the University of Massa- 

 chusetts Horticulture Research Cen- 

 ter, Belchertown, MA. Si.xty trees 

 were selected and blocked into six 

 groups (replications) of ten trees 

 each based upon crop load and 

 proximity. Trees in each block 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 24, 1992, 

 ten of the twelve trees in each 

 replication received a dilute spray of 

 225 ppm AVG applied with a hand- 

 gun, sprayed to drip. One hour after 

 application, two trees that were 

 previously sprayed with AVG were 

 washed with 6 to 7 gallons of water 

 using a hydraulic sprayer with a 

 hand gun attached. Pairs of AVG- 

 treated trees were similarly washed 

 at 4 and 8 hours after application. 

 Two trees in each block were not 

 sprayed with AVG and served as the 



untreated control trees. On September 1 7, fifteen fmit were 

 randomly harvested from the periphery of each of 30 trees 

 designated as the sample trees. Fruit were weighed, and then 

 the percent red color was estimated visually to the nearest 

 10%. Flesh firmness was measured using an Effegi 

 penetrometer with two punctures per fruit. A composite 

 juice sample collected during the pressure test was used to 

 determine soluble solids using a hand-held refractometer. 

 Fruit were then cut in half, dipped in starch iodine solution, 

 and maturity then estimated using the Mcintosh starch chart 



Fruit Notes, Volume 65, 2000 



57 



