Starry Stonewort (Nitellopsis obtusa)- Management Strategy

Written by: Brittany Williams, John North, Cole Brodeur, Mitch Dwyer

Management Plan: There are a variety of factors that show that doing nothing for the removal strategies in some areas may be the best method. In some cases, starry stonewort has already completely taken over and has extremely dense mats. With some removal efforts it can increase the chances of fragmentation and spreading the bulbils to new areas in the lake. In addition, native species such as bladderwort and coontail have actually been found to thrive in infested areas. Whereas, it has been found to outcompete non-native species such as Eurasian water-milfoil, curly leaf pondweed and fanwort (Pullman & Crawford, 2010). In areas where starry stonewort is dense and has taken over it is more beneficial to let the natural factors work itself out and eliminate the potential for fragmentation. This would mean starry stonewort covering more than 70% of the area. If there are areas where starry stonewort has recently established and has not fully taken over removal must occur. This would mean the starry stonewort plants covers only 30% or less of the area. This will eliminate the potential for the population to increase exponentially in size within a short. In Pullman & Crawfords (2010) research, they observed that chemical removal may be the better method. This will also decrease the chance of fragmentation and ecosystem disturbance. Overall, the best management plan for starry stonewort in dense areas is to do nothing, newly established areas to do chemical removal, and to increase the education and research being done.

Legal Factors: A legal implication that must be considered in Ontario is the Invasive Species Act. This act differentiates between restricted and prohibited invasive species and the actions that must be taken for particular species. Another legal implication would be the Fish and Wildlife Act and Endangered Species Act in Ontario. This would ensure that removal efforts will not cause harm to any species listed in these acts. It may also show the importance of removing starry stonewort if it is causing environmental harm to species listed. Lastly, if the chemical removal method is taken the Pesticides Act must be followed to ensure no additional harm will occur. The Pesticides Act will give more insight about who needs to have a license, who can get a license, how to get a license, and the importance of licenses according to the law. The Pesticides Act would also give more insight to information on application. This will include areas which pesticides cannot be used, when application can occur, who can physically apply them, and the volume at which can be added.

Increase Education and Research: No matter what removal plan is implemented, education and research must be increased for starry stonewort. There are three issues that currently exist with starry stonewort: lack of public knowledge, the potential for spread from human activity, and the similarity between other species leading to misidentification. To eliminate the issue of lack of public knowledge and spread from human activity increased education must occur. This can include making various booklets and pamphlets for conservation areas and environmental companies to have. This will allow the public to understand what starry stonewort is and the issues that may arise from it constantly spreading among bodies of water. In addition, having information boards at boat launch areas to lakes which either currently have or do not have starry stonewort. This will allow boaters to keep an eye out for starry stonewort and if they see a plant which may resemble it, then researchers will have an idea of areas to look out for. This will include boaters having resources of where to report these plants. This can include reporting through a website, in office at conservation areas, or through social media. It could also been done through EDDMapS, so that boaters can use the satellite imaging to have a rough idea of where the plants were. Researchers can then use these websites, EDDMapS, and in office observations. Another option which can decrease the chance of spreading among bodies of water, would be increasing the number of boat washing stations at boat launching areas. This will eliminate the chances of bulbils being stuck to motors and hulls. This may also decrease the chances of other non-native species spreading to new areas. On information boards, the impacts that starry stonewort may have on boats must be stressed. By emphasizing that starry stonewort can potentially get stuck in their motors and cause motor damage, this will show boaters the importance of using the boat washing stations. In addition to the issue of lack of awareness and spread from human activity, the increased education for researchers should also be emphasized. There are many different species in the same taxa (Chara and Nitella spp.) which means misidentifying starry stonewort is quite possible. This means that non-experts may not observe starry stonewort in an area, which can give the plant time to establish without our knowledge. A way to eliminate this issue is to increase online seminars which can be available for people doing research on starry stonewort. This will allow easy access for people to increase their knowledge of how to identify it, and eliminate the misidentification issue.

Removal of Newly Established Areas: In lake ecosystems where starry stonewort has recently established, or has very few plants, removal efforts are extremely important. By removing the small number of current plants that have established, it can eliminate the possibility of spreading in that area. In simplest terms, the two removal methods are chemical (algaecides or herbicides) or manual removal (harvesting machine). Although little research has been done on both methods, it can be concluded that chemical removal may be the better method for smaller infestations. The specifics as to which specific algaecide would be used for removal will be decided after more research. This would include the success rate on removal efforts between different algaecides. Potential algaecides to use could include: Cultrine Ultra, Hydrothol, and PondMaster products. In Michigan, mechanical harvesting was used for removal efforts in Indianwood Lake. Since the biomass was so large, the removal efforts took a long time because it was filling up the harvesting machine so quickly (Pullman & Crawford, 2010). In this particular area, it was observed that starry stonewort would actually  re- grow faster after mechanical removal than native species. This enabled a monoculture to be quickly created (Pullman & Crawford, 2010). This can be an example as to how algaecides may be a better removal method for smaller populations. By using algaecides for removal, it may decrease the ecosystem disturbance, kill plants more quickly, and be a better control (Pullman & Crawford, 2010). One major thing to note about chemical removal is sometimes it can create a “haircut treatment” where only the taller plants die off and it only reduces the height of the plant. Although this method will not completely eliminate a specific area, it can help decrease the chances of boats spreading the bulbils. This method can also be used near riparian zones of cottages, and boat launch sites to reduce the height of the plants. This will decrease chances of spread, and will increase human satisfaction for issues such as swimming, boating, and fishing. Pullman & Crawford (2010) state starry stonewort can be sensitive to common copper and endothall based algaecides and Cultrine Ultra (combined with other herbicides) can affectively suppress starry stonewort. In Stony Lake where Cultrine Ultra were used, starry stonewort did not increase and other plant species were able to reach the surface before starry stonewort entered its exponential growth phase (Pullman & Crawford, 2010). Although research still needs to be further completed as to which algaecide is the best to use, and when the prime application time is.

Conclusion: Overall, increased education and research must occur in all circumstances to increase awareness, increase proper identification, and to decrease spreading. If species are discovered sooner, then quick action can be taken to ensure spreading is decreased. In areas where starry stonewort has already taken over, it is best to leave it and allow the natural factors work itself out. In areas where starry stonewort is newly established and has not taken over, chemical removal should occur to decrease the chances of spreading.


Pullman, D., Crawford, G. (2010). A decade of starry stonewort in Michigan. LakeLine. pp. 36-42.


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