The UV vessel removes 8- to 10-foot high invasive plants from Lakeside Beach swimming area in South Lake Tahoe. (Image: UNR)

Zapping invasive weeds with ultraviolet light has been so successful that study areas at Lake Tahoe are getting larger.

“A few years ago we started off with a 4 foot by 8 foot UV array. We now have a 12 foot by 32 foot array so we can treat larger areas. We went from treating square feet to acres,” explained John J. Paoluccio, president of Inventive Resources Inc. “UNR is studying the effects on different plants. This is the first time we have been able to study the full life cycle of the plants so we can learn when it is best to treat, and how many times.”

Paoluccio first presented his technique to the Near Shore Agency Working Group in December 2015. Success was achieved starting in 2017 with a two-year pilot project by using ultra violet C light at Lakeside Marina in South Lake Tahoe. The light array is mounted under a barge that goes through the water zapping plants growing on the lake’s bottom. Plants collapsed or deteriorated in seven to 14 days.

UVC light works by damaging the DNA and cellular structure of the plants. This then stops reproduction. Because there isn’t much cellular structure the plants essentially shrivel up and decompose in a matter of days. Eurasian milfoil, curly leaf pondweed and coontail are three of the main targets.

The latest study is another two-year project. It is a private-public partnership between UNR, Inventive Resources Inc. and Tahoe Regional Planning Agency. This time a larger area will be treated.

Paoluccio said his three main goals are to: “Build a local team and construct an array that can treat an acre per day. Work more closely with the local scientists to show the benefits of treating plants with UV. See this technology be used in other locations.”

The problem with invasive plants is that they clog water ways, especially in marinas, with the Tahoe Keys on the South Shore being the worst. This can cause problems for boaters. In recent years more plants have been growing near the shoreline, making it nasty for swimmers and making what was pristine water murky.