{"id":20730,"date":"2026-06-04T11:00:00","date_gmt":"2026-06-04T10:00:00","guid":{"rendered":"https:\/\/giconmes.es\/steam-disinfection-of-substrate-and-trays-why-heat-is-replacing-chemical-fumigants\/"},"modified":"2026-06-11T05:02:24","modified_gmt":"2026-06-11T04:02:24","slug":"steam-disinfection-of-substrate-and-trays-why-heat-is-replacing-chemical-fumigants","status":"publish","type":"post","link":"https:\/\/giconmes.es\/en\/steam-disinfection-of-substrate-and-trays-why-heat-is-replacing-chemical-fumigants\/","title":{"rendered":"Steam disinfection of substrate and trays: why heat is replacing chemical fumigants"},"content":{"rendered":"\n

In any intensive farm<\/strong> – a grafted seedling nursery, a horticultural greenhouse, an ornamental nursery – the most expensive enemy is almost never visible to the naked eye. It is in the reused substrate from the previous season<\/strong> and in the growing trays that are returned to the circuit without any real treatment<\/strong>. Fungi<\/strong>, nematodes<\/strong>, phytopathogenic bacteria<\/strong>, viruses<\/strong> and weed seeds<\/strong> travel from one cycle to the next and appear when it is already too late: shrinkage in the nascence, weak seedlings, disease outbreaks that force treatment and, in the worst case, entire batches to be thrown away. <\/p>\n\n

The good news is that there is a tool that is as old as it is effective for cutting that cycle, and it is back at the center of the debate for a very current reason: water vapor<\/strong>.<\/p>\n\n

The problem of continuing to rely on chemistry<\/h2>\n\n

For decades, soil and substrate disinfection<\/strong> relied on fumigants<\/strong> such as methyl bromide. Its phasing out, agreed under the Montreal Protocol because of its effect on the ozone layer, left the industry looking for alternatives. Those that remained – methyl sodium bromide and other synthetic fumigants – have their own drawbacks: they leave residues in the environment, require waiting periods before planting can be resumed, are subject to increasingly strict restrictions on use and pose handling risks for the operator. <\/p>\n\n

In contrast, steam heat treatment <\/strong>offers a radically different approach: it does not add anything to the substrate, only applies heat to it<\/strong>. There is no chemical residue, no safety time and it can be grown again immediately. In fact, the Methyl Bromide Technical Options Committee (MBTOC) itself, within the United Nations environmental program, recognizes steam as the substitute that has replaced methyl bromide in the sterilization of substrates in most developed countries<\/strong>. <\/p>\n\n

How steam disinfects (and why it works so well)<\/h2>\n\n

The mechanism is simple to understand but requires precision to get it right. Saturated steam<\/strong> gives up a large amount of energy as it condenses on each substrate particle, raising its temperature rapidly and, above all, homogeneously: it penetrates through the pore space and reaches areas that a surface treatment would never touch. Maintaining the mass above a certain temperature threshold for a certain time is what denatures the proteins of pathogenic organisms and inactivates them. <\/p>\n\n

The key is to understand that we are not always looking for the same objective. It is convenient to distinguish three levels<\/strong>: <\/p>\n\n