27 Sep 2024

Surveys in Native and Introduced Ranges (2018–2021) for Natural Enemies of Yellow Floating Heart, Nymphoides peltata Kunth

Abstract: Yellow floating heart (Nymphoides peltata), a widespread aquatic invasive plant in the US, is currently under investigation for biological control de-velopment. From 2018 to 2021, we conducted native (Europe: 14 loca-tions; Asia: 80 locations) and introduced (US: 39 locations) range surveys to create a list of candidate agents and collect baseline infestation data for comparison. We genetically characterized populations and determined those most-closely related to US N. peltata were European. However, we found no promising agents in that region, except for previously reported fungal pathogens. In Asia, several herbivores were identified as potential agents based on observed damage in situ and previous literature reports about host specificity. These included three species of Bagous weevils, one of which may be Bagous charbenensi, and an unidentified leaf-mining Hy-drellia fly. During domestic surveys, generalist leaf-cutting caterpillars were common, similar to the native range. A major discovery was the dam-aging fungal pathogen, Septoria villarsiae, isolated from plants in a pri-vate pond in Maine—the first record in the Western hemisphere. The next steps for this program should include preliminary host specificity and im-pact assessments of S. villarsiae, the fruit-feeding Bagous spp. in China and Korea, and the leaf-mining Hydrellia sp. fly from South Korea.