Their previous work showed that the roots of pale swallowwort contain antofine, a compound believed to have some antifungal, antibacterial, and cytotoxic properties.
In further experiments, they exposed lettuce seedlings to a variety of swallowwort extracts and found that one of the extracts, which contained antofine, inhibited growth of lettuce roots.
So far, nothing in North America has halted their advance, and while eradication is no longer feasible, the researchers hope to find a biocontrol to reduce swallowwort populations.
One of the fungi being evaluated was found by a park naturalist in rural Monroe County, New York, who noticed an unusual dying off of a pale swallowwort population.
After growing for 2 weeks in a quarantined greenhouse, all three swallowwort species developed symptomatic dark-red and purple spots on their leaves.