Thrips Mortality and Strawberry Quality after Vacuum Fumigation with Acetaldehyde or Ethyl Formate1,2

Abstract

Vacuum fumigation at 560 mm Hg for 3 hr with acetaldehyde (Aa) at 1.75% in 70% CO 2 killed 100% of western flower thrips Frankliniella occidentalis (Pergande), on strawberries ( Fragaria × ananassa Duch.). However, the Aa treated berries were generally detectable in taste tests during the ensuing 3 days. Some panelists could distinguish the different taste of the treated strawberries from control samples even after 7 days. Ethyl formate (EF) in concentrations as low as 0.5% for 1 hr at 30 mm Hg pressure killed 100% of the thrips. EF fumigation affected neither taste nor odor of the berries during a subsequent 9 days of storage at 1°C. Fumigation with Aa in 70% CO 2 decreased berry decay by 69%, but EF had no effect on decay. The concentration of EF, which was determined on the day of treatment and during the ensuing 4 days, was 0.2 ppm or lower in the treated strawberries. This concentration did not differ significantly from that in the controls and is at least 100 times less than the odor threshold concentration for EF.