Effectiveness of pressurised hot water treatment (2021)

The effectiveness of hot water pressurized spray machines in field conditions to slow the spread of invasive alien species.

© Environment Agency

This study looked at the effect pressurized hot water spray had on the mortality of four invasive alien species (IAS); namely (i) floating pennywort (Hydrocotyle ranunculoides), (ii) Australian swamp-stonecrop (Crassula helmsii), (iii) killer shrimp (Dikerogammarus villosus) and (iv) zebra mussel (Dreissena polymorpha).

In field conditions, the four invasive alien species were exposed to hot water (up to 90ºC) for set durations (5-15 seconds) with varying distances (10-30 cm). During laboratory tests, 100% mortality of D. villosus and D. polymorpha were observed at the highest exposure of 90ºC water for 15s at 10cm. In comparison, H. ranunculoides fragments were exposed to both hot and cold water (18ºC) for 5s at 30cm, where 100% of fragments were destroyed. Over the following 14 days, these fragments were observed for any growth, of which none occurred. In contrast to the other three species, C. helmsii survived all treatments.

Overall, there may be a limited in field application for hot water pressurized spray machines, as cleaning associated equipment can be quite time consuming.


Bradbeer, S., Renals, T., Quinn, C.H. and Dunn, A.M. (2021). The effectiveness of hot water pressurized spray machines in field conditions to slow the spread of invasive alien species. Management of Biological Invasions 12.

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Invasive Species Ireland

Invasive Species Ireland