Red Imported Fire Ant Density in Texas Pastures with Different Grass Species

Troy Sternberg, Gad Perry, and Carlton Britton

            A noxious pest, the red imported fire ant (RIFA) continues to march across Texas, causing annual damage and expenditures of $1.2 billion statewide.  Safe and economical elimination of RIFA colonies has so far proved impossible, and new approaches to control are being sought.  One promising avenue is to identify habitat characteristics that are resistant to RIFA invasion and survival.  Although fire ants are found in high densities in most types of fields, recent research has shown that certain grasses, such as WW-B.Dahl, may be repellant to fire ants.  We have initiated a study examining RIFA density in adjacent fields planted with different grass species.

            With help from NRCS agents and local landowners, study sites have been selected that are within the range of RIFA and have pastures planted with WW-B.Dahl.  The study will cover an area approximately from Fredericksburg and Seguin in the south, Sherman in the north to Abilene in the west.  Through field research using bait cup sampling and line transect mound counts, RIFA population density will be estimated in the different grass species at each site.  The data will be analyzed to determine if certain grasses are indeed resistant to RIFA.  If so, the next stage would involve identifying the causes for this repellency.  The study is the first large-scale attempt to test the efficacy of WW-B.Dahl as a RIFA-inhibiting agent.