Steaming soil is effective in eliminating invasive alien plants (IAPs) - part II: effect of soil type.

Background: Soil disinfestation by steaming was evaluated due to its efficacy in controlling or potentially eradicating weed seeds. We exposed two soil types containing aggressive weeds to steam using a soil vacuum steaming method. The aim was to examine whether the method could be used to avoid the spreading of viable seeds to new regions when soil is reused.

Results: Dry seeds from two populations of Avena fatua and Echinochloa crus-galli and one population of Bromus sterilis, Lupinus polyphyllus, and Heracleum mantegazzianum were incorporated in a medium sandy soil and a silty coarse sandy soil and examined for thermal sensitivity. Soil temperatures in the target range of 60-99 °C, followed by a 3-min dwelling period, were tested. Increased soil temperature decreased seed germination. The two soil types did not influence the germination or viability response in most cases. For both populations of A. fatua, B. sterilis, and E. crus-galli, a soil temperature of approximately 75 °C followed by a dwelling period of 180 s reduced the germination by about 90%. Heracleum mantegazzianum was more susceptible to heat than L. polyphyllus which required more than 100 °C to reduce seed germination by 90%.

Conclusion: Soil steaming using a vacuum was an effective method to kill seeds of invasive alien plants (IAPs) in both soil types. However, the species showed different responses, indicating that steam temperature must be adapted to the specific weeds' susceptibility to heat. A temperature above 100 °C (or longer dwelling periods than 3 min) in the soil matrix might be necessary to kill all seeds. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.