The primary drug targeted and seized by the Coast Guard is marijuana, in part because it is the top illegal drug income producer, accounting for 35 percent of estimated U.S. narcotic sales in 1978. Colombia has become the main source of marijuana smuggled into the United States since the spraying of a herbicide on the Mexican crop in 1977-78 diminished Mexico's role as a supplier. The increase in maritime smuggling from Colombia since that time has been seen to a large extent on the Texas coast. One of the Coast Guard's strategies for improving its drug interdiction record is to focus its resources on interdicting 'motherships' (vessels carrying large quantities of marijuana from the source country) before the cargo can be divided among smaller boats. The most effective means of interdicting these ships is to patrol four Caribbean 'choke points,' but limited resources currently permit the covering of choke points only 18 percent of the time. While marijuana smuggling has increased across the Texas coast, the number of Coast Guard cutters and aircraft used to interdict this smuggling has not. Data on the amount of drugs seized by the Coast Guard are provided, and a map shows the identified choke points.