Frank, all three of these have an effect on alligator weed but Reward is a contact herbicide and will just defoliate the plant. 24D works fair but you probably have to hit it hard and more than once. I think Rodeo is the best for alligator weed because it is systemic, like Roundup, meaning that it is absorbed by the plant and kills it. Two things to consider. Make sure you are not diluting the chemical too much and second, make sure you use a surfactant. The surfactant is necessary to make sure the chemical is well absorbed into the leaves. Rodeo does not come with a surfactant mixed in which is what makes it different and more expensive than its sister herbicide Roundup. I typically use CideKick or Cygnet Plus. You may also find some other altenatives at a local farm supply store.