By Donald Stotts STILLWATER, Okla. – Size matters when it comes to many postemergence herbicides and effective weed control in double-cropping systems, Oklahoma State University experts said. “Once weeds become too large or crops reach particular growth stages, many weed control options are no longer viable as they may injure the crop or will not completely control target weeds,” said Misha Manuchehri, OSU Extension small grains and canola weed specialist. For example, when using a…