Evaluation of Putative Oxadiazon Resistant Goosegrass (Eleusine indica) Populations.

Herbicide resistant goosegrass, in turfgrass, was first introduced in the United States in 2003. The active ingredient was metribuzin. Oxadiazon is a preemergence herbicide that has been used for the control of annual grasses, including goosegrass (Eleusine indica), in warm season turf since the 1970’s.  Oxadiazon resistance has not be recorded in any species to date.  Having been successful for more than two decades, an absence of goosegrass control has been observed with oxadiazon rates of 3.4 to 4.5 kg ai/ha from 2009 to 2010 on a golf course in Virginia. This lead to studies being developed to observe if goosegrass plants were resistant to oxadiazon. Greenhouse trials organized in Auburn, Alabama examined oxadiazon at various rates a to discover the rate of control of goosegrass plants germinated from the seed of suspected oxadiazon resistant plants. Pots were treated with Ronstar FLO with the treatments applied at rates of 2.24, 1.12, 0.56, 0.28, 0.14, 0.07, 0.035 kg ai/ha. Specticle FLO (indaziflam at 0.0327 kg ai/ha) and Barricade (prodiamine at 0.56 kg ai/ha) were also included in the study.   Data from the study indicated that suspected resistant (SR) populations collected from Virginia were unable to be controlled with rates ranging from 0.035 to 0.56 kg ai/ha. Susceptible (S) populations were controlled with the same rates. Goosegrass was never observed in the pots treated with indaziflam or prodiamine.  The data collected suggests that the goosegrass collected from Virginia is a resistant population to various rates of oxadiazon.