Survival of invasive aquatic plants after air exposure and implications for dispersal by recreational boats

Recreational boating is widely recognized as an important vector for overland transport of invasive aquatic plants. Since their dominant form of recruitment is vegetative reproduction, entangled fragments on boats and trailers can establish new populations. The effectiveness of recreational boats as transport vectors relies on the resistance of macrophytes to air exposure. During the summers of 2012 and 2013, we conducted five field experiments in northern Wisconsin to assess air tolerance of Eurasian water-milfoil (Myriophyllum spicatum) and curly-leaf pondweed (Potamogeton crispus). We simulated conditions that these plants would experience when ensnared on boats and trailers by testing viability after drying of single stems, coiled stems, and vegetative buds (turions). Single stems of M. spicatum and P. crispus were viable for up to 18 and 12 h of air exposure, respectively. Coiling extended the viability of M. spicatum to 48 h of air exposure. Turions of P. crispus successfully sprouted after 28 days of drying. The fact that recreational boaters in the region typically visit multiple lakes within a few days suggests that most lakes are susceptible to introduction of viable plants, and so lake managers should continue to focus attention on boat cleaning.