Gloria Murillo�s one-acre farm in this central Colombian municipality looks like it met a forest fire. Her banana trees and corn stalks sag, their leaves brown. On the ground lie the charred remains of yucca, beans, rice and coffee. U.S.-supplied crop dusters have sprayed a high-octane version of Monsanto�s Roundup, killing not just her crop of coca�the raw material for cocaine�but also her family�s food crops. And the herbicide seems to have contaminated tributaries of a nearby river, the Cimitarra. Now Murillo�s four children have diarrhea and white sores. �They fumigated us like insects,�