Effect of Sprayable 1-MCP (Harvista) On Preharvest Drop and Fruit Quality of McIntosh Apples

A sprayable formulation of 1-MCP (Harvista) was evaluated to determine its influence on preharvest drop and fruit quality of ‘Gatzky McIntosh’/M.9 in 2007 and 2008.  The proprietary formulation of AVG, ReTain,  was included each year as an industry standard.  Harvista was applied at rates of 77 and 152 ppm in 2007 and 60 and 120 ppm in 2008. using a backpack sprayer propelled with CO₂ at 40 PSI one week before the anticipated start of the harvest.  A split application of Harvista of 60 ppm was also used in 2008.   Silwet L-77 at 0.05 % was included with the Harvista in both years and a 1% summer oil was used only in 2007.  ReTain was applied with Silwet L-77 3 weeks before anticipated start of harvest at 106 ppm.  The Harvista and ReTain treatments were applied to 2 sets of trees.  Harvest evaluation and storage samples were taken from one set of trees.  No fruit were harvested from the second group of trees and they were used to assess treatment effects on preharvest drop.  Harvista and ReTain controlled preharvest drop comparably and effectively through the third week of September.  Harvista at both concentrations controlled drop more effectively than ReTain for an additional week.  Harvista and ReTain delayed the onset of the climacteric and the development of red color, but they had little influence on fruit flesh firmness, soluble solids or starch rating.  The split application of 60 ppm Harvista significantly lengthened the period when drop was inhibited.  The only treatment that improved postharvest storage life of fruit was when trees received two applications of Harvista and the storage sample was taken immediately after the second Harvista application.