Phylloxera is a root aphid that can kill grapevines. There are other root feeding aphids on herbaceous plants that are harmful to the plant, because they suck the sap out of the roots. There are a few websites on aphids; here are two examples. http://ctr.uvm.edu/ctr/el/el60.htm; http://entowww.tamu.edu/extension/bulletins/uc/uc-031.html Regards, Christiane
