Water chestnut was first recorded in North America near Concord, Massachusetts in 1859. Since that time, wild populations have become established in many locations in the Northeastern United States. Water chestnut was recorded for the first time in the Bird River in Baltimore County in 1955. The Maryland Departments of Game and Inland Fish and Tidewater Fisheries used mechanical removal and chemicals (the herbicide 2,4-D) to control the population.
In 1964, water chestnut reappeared in the Bird River and an additional 100 acres were discovered in the Sassafras River in Kent County. Thirty acres were mechanically removed from the Sassafras River in 1964. A combination of removal techniques were used once again in 1965, when 200 acres were eradicated on the Sassafras.
The harvesting efforts were believed to have been successful, and no plants had been reported until the summer of 1997 when a landowner on the Bird River noticed an unusual plant. This led to the discovery of a small population of water chestnut in a cove just upriver from Railroad Creek. From the summer of 1997 to the summer of 1998, these plants expanded from 3 acres to approximately 30 acres, and reports were also received of water chestnut growing in Lloyds Creek of the Sassafras River. Both populations were in the same locations from which water chestnut had been harvested in the 1960's, suggesting that this was a resurgence of the same population of plants.
The Maryland Department of Natural Resources has been attempting to eradicate water chestnut from the Bird River, Harford County and the Sassafras River, Kent County since 1999. The population in the Bird River had spread from approximately 50 plants in the summer of 1997 (based on conversations with local landowners) to over three acres in 1998. By this time, the three-acre area was so heavily covered with plants that the water beneath the plants was barely visible. The Sassafras population was believed to be slightly larger, but determining the exact quantity was not possible.
Based on conversations with aquatic plant control experts from around the country, it was decided that application of the herbicide 2,4-D would be a safe and effective control technique. Despite this advice, public and state concern over the application of an herbicide to Chesapeake Bay waters lead the department to save herbicide application as a last resort in the event that other techniques didn’t work. It was decided to launch a large mechanical and hand removal effort. This effort has been ongoing since 1999. This control has prevented water chestnut from becoming a nuisance to water contact recreation, but total eradication has not been possible. Below are brief annual summaries of efforts to date.
* In 1999, the harvest on the Bird was 140,000, 260,000 on the Sassafras. In 2000, 1000 bushels were harvested on each river.
Figure 1. Bird river water chestnut locations. Historic coverage is in red, 2018 distribution in green.
Figure 2. Sassafras River water chestnut locations. Historic coverage is in red, 2018 infestations are in green.
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