Seed Germination and Reseeding Interval of Cool-Season Turfgrasses Following Methiozolin Application.

The effect of methiozolin (‘PoaCure’) on seed germination and its persistence following application has had limited research.  The effect of herbicide rate and species on germination and reseeding interval needs to be determined.  A laboratory AOSA protocol germination was done with Poa annua and Agrostis stolonifera using PoaCure at 0, 0.125, 0.25, 0.5, 1, and 4 L/ha product.  For both species, 21 d germination (% of control) was 0% at 4 L/ ha, <5% at 1 and 0.5 L/ha, <20% at 0.25 L/ha, and <50% (A. stolonifera) and <80% (P. annua) at 0.125 L/ha.  A greenhouse study to determine reseeding interval following PoaCure application was also conducted.  PoaCure was sprayed onto a soil medium (90% sand:10% peat moss) at 0, 4 L/ha product, 4 L/ha + 4 L/ha (2 wk interval), or 4 L/ha + 4 L/ha + 4 L ha^-1 (2 wk intervals).  Seed (P. annua, P. pratensis, Lolium perenne, or A. stolonifera) were planted 4, 8, 12, 16, or 20 wk after last treatment (WALT) and seedling emergence counts were made 1, 2, 3, and 4 wk after each planting.  A. stolonifera was also evaluated at 2 L product ha^-1 utilizing the above protocol.  Experimental design was a randomized complete block with 4 replicates.  Low rates of PoaCure markedly reduced seed germination of P. annua and A. stolonifera.  PoaCure at 4 L ha^-1 reduced emergence of P. annua for 12 WALT and with multiple 4 L ha^-1 applications for 20 WALT.  A. stolonifera, L. perenne, and P. pratensis all had some emergence 16 WALT; however, the seedlings appeared quite stunted and many of these seedlings probably would not survive.  A. stolonifera emergence was greater at 2 L ha^-1 than at 4 L ha^-1.  Field work is needed to verify these results.  Turfgrass managers need to be mindful that reseeding may not be an option for some time following any application.