Study of the selectivity of PRIMSTAR (fluroxypyr + florasulam) in two key grass species (FESRU & LOLPE) grown for seed production.

PRIMSTAR is a SE (Suspo-Emulsion) formulation containing 2.5 g florasulam & 100 g fluroxypyr-MHE per liter. PRIMSTAR is registered in Belgium since beginning 2003 as selective herbicide to control the most important broadleaved weeds in wheat & barley. The weed-spectrum of this product is now completely evaluated. Nevertheless, it was interesting to study this product in grass seed production. The prime objective of this study was to investigate the crop safety of PRIMSTAR applied on the two key species of grass produced for seed. The two species in the study were: 1) FESRU--Creeping fescue Festuca rubra rubra cv. NEVSKI sown at 15 kg/ha, June 6, 2001. 2) LOLPE--Perrenial ryegrass Lolium perenne cv. MERBO sown at 17.5 kg/ha, October 5, 2001. The trial was a randomized complete bloc design in 4 reps. The contractor was REDEBEL, a GEP registered independent company. The trial site was located in Melle, Belgium. PRIMUS 100 mL, PRIMUS 200 mL, PRIMSTAR 1.05 L/ha, PRIMSTAR 2.1 L/ha, BASAGRAN DP 3 L/ha, BASAGRAN DP 6 L/ha. The treatments were applied March 29, 2002 on a maintained weed-free field. PRIMSTAR appeared to be highly selective in FESRU & LOLPE intended for seed production. All evaluations observed were positive. Only some light visual crop injuries were possible, but mostly negligible and the symptoms disappeared very soon within 35 DAA. Treatments with PRIMSTAR had no effect at all on the main seed yield characteristics i.e. seed yield, thousand seed weight and germination power. Treatments with the reference BASAGRAN DP (bentazone + dichlorprop) brought about a more aggressive action in comparison with the PRIMSTAR treatments in terms of vegetative crop inhibition (reduced straw yield for perennial ryegrass).