Abstract
An array of vectors have been identified that pose a risk of spreading invasive alien species (IAS), from personal protective equipment to large equipment such as vehicles and boats. Biosecurity practices that remove and/or kill IAS reduce the risk of accidental spread. The effectiveness of biosecurity protocols suitable for large equipment is little tested and requires development. One widely-used biosecurity method for large equipment is high-pressure hot water spray machines. This study tests the effectiveness of high-pressure hot water spray to induce mortality in two invasive aquatic plants: floating pennywort (Hydrocotyle ranunculoides) and Australian swamp-stonecrop (Crassula helmsii); and two invasive invertebrates: killer shrimp (Dikerogammarus villosus) and zebra mussel (Dreissena polymorpha) in field conditions. IAS were exposed to hot water spray for a range of durations (5–15 seconds) and from a range of distances (10–30 cm). Further treatments of up to 90 seconds were applied to C. helmsii. Complete survival of D. polymorpha, D. villosus and C. helmsii was seen in all control treatments following exposure to cold water spray. Hot water spray caused complete mortality of D. polymorpha and D. villosus at 10 cm for 15 seconds, demonstrating the effectiveness of the hot water treatment in inducing mortality. However, treatments were less effective when applied at longer distances and shorter durations. In contrast, hot water spray was ineffective in causing mortality in C. helmsii, even at 90 seconds of exposure. Fragmentation and complete mortality was seen in H. ranunculoides following exposure to hot and cold water spray, therefore the pressure of the spray was associated with H. ranunculoides mortality. The use of hot water spray is effective against the aquatic invasive animals tested here, however to ensure complete mortality, the importance of both duration and distance of hot water spray application is highlighted. Hot water spray did cause complete mortality in H. ranunculoides but not in C. helmsii, therefore the need for treatment water containment and safe disposal is paramount to prevent spread of potentially viable propagules.
Highlights
The impacts resulting from the introduction and spread of invasive alien species (IAS) are of growing concern for a range of stakeholders
High mortality of D. polymorpha (> 80%) was seen following hot water spray treatments of 10 seconds from 10 cm and 15 seconds from 20 cm (Table 3b). For both invasive animal species further mortality was observed 72 hours post exposure, complete mortality was not achieved in any treatments that had incomplete mortality at 24 hours
Following the identification of the effect of hot water treatment on IAS mortality, we explored the maximum temperature and total thermal exposure during each treatment to confirm the thermal differences between treatments
Summary
The impacts resulting from the introduction and spread of invasive alien species (IAS) are of growing concern for a range of stakeholders. In line with the Aichi Biodiversity Targets (Target 9), the spread of freshwater IAS and associated dispersal corridors throughout Europe has been well documented over recent decades (Bij de Vaate et al 2002; García-Berthou et al 2005; Leuven et al 2009; Gherardi 2010; Convention of Biodiversity 2020) Informed by this and with the aim of preventing further spread and introductions of IAS, regulation and framework have been introduced both at the international and national levels (e.g. EU Regulation, GB Strategy; UK Parliament Act 1981; European Union 2014; Department for Environment, Food and Rural Affairs 2015). Prevention of introduction and secondary spread is key to this regulation
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