Picloram PERSISTENCE AND BREAKDOWN Persistent in soil;half-life may be 1 year or more,but it is typically 90 days or less in the South in favorable conditions Breakdown is by photolysis Mistretta USFS R-8 Picloram PERSISTENCE AND BREAKDOWN Persistent in soil; half-life may be 1 year or more, but it is typically 90 days or less in the South in favorable conditions Breakdown is by photolysis Mistretta USFS R-8