Radiant heater effects on Leontodon taraxacoides, Hypochaeris glabra, and Parentucellia viscosa in dunes and seasonal swales at Humboldt Bay National Wildlife Refuge

Radiant heaters are devices used to control unwanted plant species. This study explores whether radiant heat treatments can be an effective management tool for controlling invasive plant species Leontodon taraxacoides, Hypochaeris glabra, and Parentucellia viscosa in dune ridge and swale environments at the Lanphere Dunes Unit, Humboldt Bay National Wildlife Refuge. Experiments were conducted in 2005 and 2006. The experiment of 2005 was designed to determine the effect radiant heating would have on Leontodon taraxacoides and Hypochaeris glabra survival. Field observations in 2005 indicated that seed set of Leontodon taraxacoides could be reduced by radiant heating. A fecundity experiment was designed in 2006 to quantify this reduction. A third invasive species, Parentucellia viscosa, was common in the plots and responded to the treatment. The effectiveness of radiant heating treatments on this species was observed and quantified. Results of this study indicate that radiant heating does not generally kill Leontodon taraxacoides individuals outright, but does significantly reduce seed set when treatment occurs immediately prior to flowering. Parentucellia viscosa is effectively controlled by radiant heating, as individual plants are killed after treatment and do not set seed. Hypochaeris glabra is not generally killed by radiant heating, but the treatment seemed to have an effect on future recruitment.