Phase out of 95% of the key ozone depleting chemicals, including methyl bromide (MB), under the Montreal Protocol has been the greatest present day success for the environment and mankind. Additionally, last year after 7 years of debate, the Kigali amendment was ratified bringing in stepwise reductions for HFCs which means one third of anthropogenic effects on the climate will be avoided. The key success to date has been the reported phase out of 98% of MB for controlled uses which has led to 35% of the present ozone layer recovery. It has also had a huge impact on plant pathology and contributed to a major rethink of control methods for soil borne pathogens and weeds in a huge number of horticultural sectors. Approximately 80% of the 75,000t of MB used worldwide was for soil disinfestation for control of a wide range of soilborne pathogens and weeds. Since then, most sectors in countries globally have moved to other chemical methods, but also some more sustainable solutions. Key chemical alternatives being used today are generally old products applied with new methods i.e. 1,3-dichloropropene, chloropicrin and metham sodium either applied alone, as mixtures or as sequential applications, however they are subject to increasing regulations and bans, e.g. new VOC regulations, increased buffer zones, township caps, etc. and their future is questioned. Several new products, dimethyl disulphide and ethane dinitrile are proving effective, whilst others have failed to gain acceptance, viz; furfural, Na azide, propargyl bromide and propylene oxide. More sustainable solutions include grafting, plant resistance and soilless culture, although the use of disease suppression is still a major challenge for plant pathologists. Some industries unfortunately are now faced with increased pressure from specific diseases, eg. Macrophomina on strawberry fruit, Nacobbus nematode on tomatoes.
Approximately 10,000 t of MB are stilled used for Quarantine and Preshipment uses which are exempt from phase out under the Montreal Protocol owing to countries concerns over global trade, phytosanitary issues and the need to maintain national biosecurity. The impact of the these regulations on MB will be discussed.