Waterweed adventures in America

Megan Reid with Prof James Cuda (Photo: James Harrison)
Megan Reid with Prof James Cuda (Photo: James Harrison)

Megan Reid, CBC Masters student, has recently returned from a productive three-month stint in the USA. Her mission? Conducting surveys for natural enemies and potential biological control agents of Mexican water lily (Nymphaea mexicana), which has become an invasive species in South Africa.

‌After months of planning and a journey that lasted over 24 hours, she arrived in Fort Lauderdale, Florida, preparing to begin an incredibly busy, educational three-month journey. With the help of the employees of Dr Lyn Gettys’ aquatic plant research lab, as well as Dr James Cuda from the University of Florida, and Dr Phillip Tipping from the US Department of Agriculture, she travelled around Florida seeking natural populations of Mexican water lily in the US waterbodiesMegan’s first stop was Lake Okeechobee, which is the ninth largest natural freshwater lake in the United States – needless to say its size was rather staggering (especially to a South African) and even after half a day searching for Mexican water lily, not a single plant was found! Not only that, but with the hurricanes and changing water levels it was important to speak to people who knew exactly where the populations were. So after consulting various biologists who work for the Florida Fish and Wildlife Conservation Commission, Megan received some valuable guidance and assistance, and with a subsequent change to her survey strategy, she had much more success in locating populations.

‌Most of Megan’s time was spent in Florida, but she also spent a few days working in Weslaco, Texas. Megan initially found some insects causing damage to N. mexicana however, they all appeared to have a broad host range. Time was ticking and Megan was worried that she would not find an insect that had high potential to be a host specific biological control agent for the targeted Mexican water lily. However, at Baton Rouge, Louisiana, her luck changed. Here, she finally found a weevil which seems to have good potential to be a biological control agent in South Africa.

The weevil is Bagous americanus from the family Curculionidae. The adults of this species feed on the leaves and oviposit in a feeding scar. Once hatched, the larvae mine the leaf towards the petiole, and from there they mine into the stem and pupate before emerging as adults again. Bagous americanus has been recorded on another plant species, Nymphaea odorata (white water lily) which is also exotic in South Africa, and one paper by Greg Cronin and his colleagues in 1998 suggests that at the very least, B. americanus seems to be specific to the genus Nymphaea.

The well-travelled weevil, Bagous americanus, which Megan brought back to Grahamstown, is now safely in quarantine at the CBC at Rhodes University. Megan’s next step is to begin host specificity testing in order to determine the feeding range of the weevil and whether it will be safe for release in South Africa. Good luck Megan!

Source:  Megan Reid and Esther Mostert

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