- Author: John Madsen
- Posted by: Guy B Kyser
On a conference trip to New Zealand in 2018, I was able to finally meet the final member of the invasive Elodea family, or Hydrocharitaceae. In the United States, we already have the invasive hydrilla (Hydrilla verticillata from Asia) and Brazilian elodea (Egeria densa). Not to be undone, we have contributed to worldwide waterweed problems with “North American” elodea (Elodea canadensis, or Canadian waterweed). The final weedy elodeid is African elodea (Lagarosiphon major), which is an invasive weed to New Zealand and Australia. While it is native to tropical Africa, it can form nuisance problems in South Africa. African elodea is not yet found in North America, but vigilance is required...
- Author: John Madsen
- Posted by: Guy B Kyser
The Delta Region Areawide Aquatic Weed Project (DRAAWP) was represented by two presentations to the 15th International Symposium of Aquatic Plants, held February 18-23 2018 in Queenstown, New Zealand. “Quantitative techniques for assessing changes in distribution and abundance of aquatic plants after management” was presented by John Madsen, and “Improving aquatic plant management in the California Sacramento-San Joaquin Delta” by David Bubenheim. These two presentations were among the 75 presentations and dozen posters during the Symposium, held every three years. Presenters from Europe, Asia, North America, Australia, and New Zealand presented research on aquatic plant biology, ecology, and...
- Author: John Madsen
- Posted by: Guy B Kyser
We were sampling plots in the Delta in July 2016, and found a small clump of this plant – pickerelweed (Pontederia cordata). Generally considered a desirable native wetland plant, it happens to fall in the same botanical family as the baddest of the bad in the Delta – waterhyacinth (Eichhornia crassipes). What does family mean in the botanical world, anyway? Although native here, pickerelweed is at best considered “occasional” in the Delta. Waterhyacinth falls somewhere between “abundant” and a “scourge,” depending on the year of reference. While there are a number of similarities in appearance (particularly in the characteristics of the flower, which is the original...
- Author: John Miskella
- Posted by: Guy B Kyser
Waterhyacinth (Eichhornia crassipes) is a floating perennial species that has become a serious management issue as it invades aquatic ecosystems around the world. In the Sacramento-San Joaquin Delta in California, the species forms large, dense mats on the water surface that inhibit boating, fishing, water access, and decrease light availability below the floating mat.
While the leaves of waterhyacinth generally turn brown and die during the winter, many waterhyacinth plants survive the winter and grow new leaves in the spring. Warmer spring temperatures also cause the plants to grow stolons, or spreading stems, from which daughter plants grow (Figure 1). Stolon growth is a key driver of waterhyacinth...
- Author: Sharon Lawler
- Author: Maribel Portilla
- Posted by: Guy B Kyser
Mosquito research by Maribel Portilla and Sharon Lawler recently included an experiment on how Egeria, or Brazilian water weed, affects mosquito populations. Egeria is a submersed aquatic weed that can cause problems in channels and irrigation waterways. Mosquitoes also breed in stagnant waters, but, we asked, is this because of the weeds?
We used large cattle-watering tanks to simulate stagnant, back-water areas with and without infestations of Egeria (Figure 1). Five tanks had no weeds, five had healthy Egeria, and five had Egeria that was sprayed with the herbicide fluridone. We added zooplankton and insects colonized naturally.
Interestingly, there were fewer...