Yellow Nutsedge – A warm season perennial plant that looks like yellow grass, but is actually a sedge.  It emerges in poorly drained areas or areas that irrigate too frequently!!!  Light frequent irrigation makes nutsedge problems 90% worse than deep, infrequent irrigation!!  If you get several thunderstorms during May, nutsedge is inevitable.  Since it is a perennial, crabgrass pre-emergent has no effect on nutsedge.  There are two decent herbicides that (IF APPLIED PROPERLY) can control nutsedge.  They are Sedgehammer or Dismiss.  Dismiss is the newer and better herbicide.  It controls nutsedge often with one application where as Sedgehammer always takes at least two apps.  Make sure to follow the label with all herbicides!  Dismiss will stunt desirable grasses for up to a year or kill them if over applied.  We spot treat for nutsedge during third app each year and every time we apply preventative fungicide.  Nutsedge tends to keep germinating in the same spots every year, all summer long.  DO NOT pull it out of the ground.  This often leaves the “nut” in the soil and causes rapid proliferation of more sedge.  it is like pruning a shrub, it stimulates rapid growth!!  if you do pull it, make sure you get the whole plant!!!