Diphenylamine and Conditioning Affect Disorders in Controlled Atmosphere (CA) Stored ‘Honeycrisp' Apples

‘Honeycrisp’ apples store well at 3 °C in air after a conditioning week at 10 °C to reduce risk of soft scald development, but may become bland after several months.  Controlled atmosphere (CA) storage maintains firmness and acidity but there is variation in susceptibility to internal carbon dioxide injury among orchards, making it too risky to recommend.  We have investigated the effects of diphenylamine (DPA), with and without conditioning, on CA storage of ‘Honeycrisp’ from two orchard blocks in each of three growing regions in New York.  In a separate experiment, fruit quality after CA delays up to 28 days along with the use of DPA, 1-MCP, or both has been investigated.  Results indicate that the week of temperature conditioning is essential for maintaining fruit relatively free from soft scald (found only in some orchard blocks) and lowered the incidence of internal carbon dioxide injury if the fruit was not treated with DPA.  DPA use strongly reduced or eliminated internal carbon dioxide injury.  If DPA was used on fruit susceptible to soft scald, but without a conditioning week prior to CA, the soft scald was still present but less severe.  However, DPA treatment increased the amount of decay and aerosol or thermofogging options for DPA treatment may be needed to avoid unacceptable losses.