Use of measured concentrations of acetic acid vapour to control postharvest decay in d’Anjou pears

Abstract

Decay of d’Anjou winter pears caused by Botrytis cinerea is a major problem for pear growers in North America. Acetic acid (AA) vapour could be an alternative to the use of postharvest fungicides such as thiabendazole for disease control. In fall 1998, bin lots of pears, half inoculated with B. cinerea, were fumigated with mean rates of 292 μl l−1 h AA vapour, three times over a period of 7–15 days and once with 586 μl l−1 h AA vapour. Similar trials with AA vapour rates averaging 198±39 μl l−1 h were conducted in 1999 and 2000. Treatment effectiveness was evaluated immediately after fumigation by monitoring fungal microflora on fruit surfaces and stems and after storage by recording number of decayed fruit and stems infected by species of Botrytis or Penicillium. Application of AA vapour reduced both stem and fruit surface microflora to low levels and in some cases to zero initially and after the fruit had been stored for 4 months, reduced rot by 51% on fruit inoculated with B. cinerea. Overall analysis of data from the 1998 trials showed that AA fumigation significantly reduced stem infection on fruit stored in air or controlled atmosphere storage. A trial conducted in 1999 at a commercial site established the lower rate of 198 μl l−1 h as an effective rate; fruit rot was reduced from 36 to 3% in fruit inoculated with B. cinerea and stored for 4 months. Two consecutive fumigations at 200 μl l−1 h AA vapour in 2000 on naturally contaminated fruit reduced stem infection by 43% and increased the number of mold-free fruit by 44% without any damage to the pears. The consequences of using measured amounts of AA vapour to control postharvest decay of pear are discussed.