The Madsen lab is working on South American spongeplant (Limnobium laevigatum), a relatively new invader in the Sacramento-San Joaquin Delta (Photo 1). Spongeplant is a floating aquatic weed that somewhat resembles waterhyacinth and can be found alongside waterhyacinth in backwaters and along river edges. Photo 2 shows the spongy, air-filled underside of the spongeplant leaves, which allow them to float on the water surface.

Photo 3 is from a trial measuring the spread of South American spongeplant over the water surface at different water temperatures in the laboratory. This will help us to predict the timing of growth in the field, which will inform management decisions.

Photo 4 shows a spray chamber application of herbicide to South American spongeplant, part of a small-scale screening trial to measure efficacy of different herbicides on this species. We hope to use these results to scale up to a field trial next season.

This is a project with the John Madsen aquatic weeds lab with USDA-ARS Invasive Species and Pollinator Health Unit.