I tried growing rutabagas one year and they got eaten something terrible by aphids. I tried spraying soapy water to deal with them. The soap was Dr. Bronner's. The soap made the rutabagas taste like soap and the aphids would come back in force within a day or two anyways. So that would be my fear with using it on tobacco. I wonder about using diatomaceous earth on tobacco but I'm sure it can't be good to inhale. Some people here hose their plants down with plain water. The idea being to knock the aphids off of the plants. Since we are talking about tobacco, I wonder about making a tea from tobacco and spraying that on the aphids. Sounds strange, I know but I've done that for aphids on corn and it worked.