Research on starry stonewort treatments informs management efforts

A forthcoming paper from MAISRC researchers and their collaborators will help inform starry stonewort management efforts in Minnesota lakes. Researchers found that mechanical and algaecide treatments greatly reduced starry stonewort biomass, but that bulbils – small, star-shaped structures that can regenerate into new plants – remained viable after treatment.

The project consisted of both field and lab work to evaluate the effects of mechanical and algaecide treatments on starry stonewort biomass, bulbil density, and bulbil viability. Researchers examined several areas of the lake that had undergone different treatments, including a channel that was mechanically harvested, an area that was treated only with algaecide, and an area that was first mechanically harvested and then treated with algaecide. The results of each treatment were compared to an untreated reference area. This research was conducted in collaboration with the Koronis Lake Association and Blue Water Science, a lake management firm. Key findings included:

  1. The algaecide (chelated copper) treatment on its own significantly reduced starry stonewort biomass, but failed to reduce bulbil density and the capacity of starry stonewort to regenerate via bulbils.
  2. Combining the algaecide treatment with mechanical harvesting also significantly reduced starry stonewort biomass, and was associated with lower bulbil viability.

These findings underscore that a multi-pronged approach to starry stonewort control that includes both chemical and mechanical management has potential to improve outcomes. Determining how to prevent the recovery of starry stonewort from bulbils that remained viable after treatment needs further investigation.

Applied research on the efficacy of starry stonewort treatment options has been extremely limited; MAISRC is filling a critical knowledge gap with this work. The paper will be published in Lake and Reservoir Management this spring.

This invasive alga has now been found in eleven Minnesota lakes and can grow tall and dense, interfering with recreation and potentially displacing native species. To date, treatment options have been limited and the species has proven difficult to control. Stay tuned to our website for more information and updates about starry stonewort.


- Minnesota Aquatic Invasive Species Research Center (MAISRC)