The reason they need weevil greenhouses is that the Brazilian weevils don't like Texan winters, and tend to die off over winter. If they mentioned it in this video I missed it.YouTube
Salvinia is a tricky beast—it doubles in size every four-five days, has tentacles that loom underneath, and chokes up waterways, making it impossible for wildlife to grow or boats to sail. It’s a monster currently devastating Texas’s picturesque Caddo Lake. But, never fear, the weevil is here. Residents of Uncertain, Texas have taken it onto themselves to combat the invasive species with the help of a small Brazilian insect known as the weevil. By releasing these tiny soldiers onto the pervasive plant, they’re hoping to save the lake and their home.