Thanks Ray. You are correct. I am not doing a thorough job in cleaning the plants. The reason for this is because I cannot remove the plant and many of its pbulbs and roots are not accessible to my large bulky hands.
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"We must not look at goblin men,
We must not buy their fruits:
Who knows upon what soil they fed
Their hungry thirsty roots?"
My son works at Nature's Control (the first link D posted). I can ask him if he thinks they really do a good job, and how long it usually takes if you like.