Begin monitoring when flag leaf is visible. Take 10 stem samples from several locations in field margins and from the center portion of your field. Examine the flag leafsheath carefully for adults and immatures and determine the average number of adults and total thrips per sheath. Taller, more mature plants will likely have higher numbers of thrips, so be sure to take a random sample. The threshold for adults is two to four per flag leaf sheath or 30 to 60 total adults and immatures per leaf sheath.
Treatment is more economical in the boot stage.
Because barley thrips move into a field from field edges, you may be able to strip-spray field edges rather than the entire field. Parathion is the only insecticide registered for use on barley thrips and requires a closed transfer system. The restrictions on its use include 15 days to grain and three days for re-entry. Remember to always read the label. Grasshoppers are very delayed in development because of weather, but they still have been sighted.