The Role of Methyl Bromide Phase-Out on Charcoal Rot of Strawberry in Australia

Charcoal rot of strawberry caused by the soilborne pathogen Macrophomina phaseolina has increased in importance in Australia and many other countries since 2005. Several factors might explain the increase in the disease in Australia, including the withdrawal of the soil fumigant methyl bromide in 2005 due to its adverse effect on the stratospheric ozone. We conducted a field experiment to test the hypothesis that soil disinfestation with methyl bromide could eliminate charcoal rot in a strawberry field severely affected by the disease. The results showed that a single application of methyl bromide/chloropicrin reduced M. phaseolina in infected strawberry crowns buried in soil by 98% and DNA concentrations in soil at planting by 100% compared with the untreated control. The use of methyl bromide/chloropicrin also reduced charcoal rot in the strawberry crop by 99.7% and increased marketable fruit yields by 86% and revenue by A$2.81 per plant. In contrast, the adopted substitute fumigant, 1,3-dichloropropene/chloropicrin, controlled M. phaseolina and charcoal rot considerably less effectively than methyl bromide/chloropicrin. The results add weight to the premise that the phase-out of methyl bromide was an important factor that contributed to the increase in charcoal rot in strawberry in Australia and possibly in other countries. The benefits of methyl bromide withdrawal for the environment are significant and well documented, so the ongoing need to identify suitable alternatives for managing soilborne diseases such as charcoal rot remains vitally important. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .