Bogota, Colombia ? They’ve tried drug seizure. They’ve sprayed herbicides. It keeps growing.

The United Nations said Tuesday that despite these efforts, growth in Colombia of the plant used to make cocaine is up by 8 percent – to 330 square miles.

Authorities have sprayed coca fields totaling 25 times the size of Manhattan.

Colombia is the world’s largest cocaine producer. The biggest increases were in the lawless, largely uninhabited jungles near its borders with Venezuela and Ecuador. Colombia is believed to be the source of 90 percent of the cocaine consumed in the United States.

The studies are strong evidence that the No. 1 weapon in the U.S.-led war on drugs – aerial fumigation of coca fields – might not be working. The U.S. goal is to halve coca production in the Andes.