Evaluation of post-harvest treatments for eradication of Erwinia amylovora from apple fruit

Abstract

Fumigation with methyl bromide or propylene oxide, or immersion in sodium hypochlorite, chlorine dioxide, benzalkonium chloride, acetic acid or citrate buffer, were evaluated as potential eradication treatments for Erwinia amylovora on mature apple (cv. Red Delicious) fruit. Methyl bromide, chlorine dioxide and propylene oxide were relatively ineffective and were not tested further. Mature apple fruit were artificially inoculated with 2·52 × 10 7 to 1·63 x 10 8 cells per fruit, dried, then immersed in 250 ppm NaOCl in 500 ppm dodecylbenzenesulphonic acid (DBSA), 0·1 m citrate buffer, pH 2·5, in 500 ppm DBSA, 2000 ppm benzalkonium chloride in 2500 ppm Ortho X-77, tap water, or were not immersed. The log 10 average number of colony-forming units recovered (from 30 fruit replicated five times) after treatment were: sodium hypochlorite, 1·19; citrate buffer, 1·50; benzalkonium chloride, 1·83; water washed, 3·79 and untreated, 4·71. The percentages of fruit from which E. amylovora was not recovered after treatment were: citrate buffer, 67%; NaOCl, 50%; benzalkonium chloride, 36%; tap-water wash, 6% and untreated, 0·8%. Citrate buffer, benzalkonium chloride and sodium hypochlorite gave significant reductions in surviving E. amylovora cells and in percentage of fruit from which E. amylovora was not recovered.