I've seen this method used to capture invasive species in Hawaii, but they actually take a pipe, just big enough for the froggies to fit in, and they either tie them to the tree trunks, or the stab them into the dirt around the bank so they stick up. Control of Coqui Frog in Hawai'i I've tried it to catch gray tree frogs with no success, but it was the wrong time of year, and my pipes were probably too big... Who knows, you might get lucky!