I have greatly reduced goatheads here at my house in Alpine. For two years I have pulled and pulled and pulled. I have also applied dry molasses at 100/lbs per acre twice, late summer as they germinate in the fall. Below is a link to some folks who sell a biocontrol (weevil). I haven't tried it and probably won't. It is my understanding that if you are going to try the weevil you should be sure the suppllier has established protocols to prevent infection of the weevil with mites.