It may be widely understood that most aquatic and wetland weeds are spread by water currents, but the patchwork of colonizing exotic plants can be puzzling. Why do weeds establish in some places but not others? Generally, the number of propagules (seeds or plant fragments) moving in a watershed is assumed to increase downstream. This assumption influences management decisions, such as prioritizing management efforts between upstream and downstream areas of a river to reduce reinvasion.

Uruguay waterprimrose (Ludwigia hexapetala) is an emergent aquatic weed from South America which has invaded many riverine wetland ecosystems in the western US and Europe. This is a clonal plant which can reproduce asexually via shoot...

We are doing a trial of eleven aquatic herbicides for their potential to control Brazilian waterweed (Egeria densa). The active ingredients being tested are bispyribac sodium, carfentrazone, copper-ethylenediamine complex, diquat, dipotassium salt of endothall, the dimethylalkylamine salt of endothall, florpyrauxifen-benzyl, flumioxazin, fluridone, imazamox, and penoxsulam. The study is a twelve-week static exposure of a single initial treatment, using all of the 50 tanks in the mesocosm facility. While not all of these aquatic herbicides would be allowed in the Sacramento/San Joaquin River Delta, we should at least know what might be useable in other habitats near the Delta. Currently, California State Parks Division of...

Water hyacinth (Eichhornia crassipes (Mart.) Solms)) is a perennial free-floating aquatic plant species native to the Amazon region of South America. It has become invasive around the world, including the Sacramento-San Joaquin Delta in central California. Water hyacinth can disperse and colonize new locations by floating on the water surface. The intertwined root and leaf structure allows the plants within a mat to remain held loosely together, while occasionally separating into smaller mats (Figure 1).

From June 2016 to Feb 2018, a study was done to determine to what extent wind, tidal movement, and water flow from the San Joaquin River drove the dispersal of water hyacinth mats in the Delta. Two-liter...

One of the many advantages of being part of DRAAWP is the multiple occasions to meet and work with people from a variety of backgrounds. There have been many opportunities to interact with a variety of disciplines, from satellite imaging and economics to water chemistry and weed control. Thanks to this integrative approach, the Lawler Lab at UC Davis is uniquely situated in a position where it is able to provide a large diversity of undergraduate students the chance to try research first hand. This is particularly special, because this training is often their first exposure to scientific research, either in the lab or in the field. It has been a formative experience for many of the interns, right at the beginning their scientific...