EFFECTS OF TRINEXAPAC-ETHYL (MODDUS) IN SEED PRODUCTION OF EIGHT TEMPERATE GRASSES
The plant growth regulator (PGR) trinexapac-ethyl (Moddus), was evaluated in 37 seed production trials from 1998 through 2002. On average for five timothy (Phleum pratense) trials in the relatively wet and cool climate of Central Norway (63 64°N), Moddus (150 g a.i. ha-1 at the late flag leaf / early heading stage, GS 45 51) increased seed yields by 52% over the unsprayed control and 25% over CCC sprayed plots. In the main seed production district in southeast (SE) Norway (58-61°N), average seed yield increases by Moddus (150 g a.i ha-1 at the first to second node stage, GS 31-32) were 18% in timothy, 43% in cocksfoot (Dactylis glomerata), 36% in common bent (Agrostis capillaris) and 21% in meadow fescue (Festuca pratensis). Compared to the effects of CCC (2.0 kg a.i ha-1 at GS 31-32), these increases were slightly lower in timothy, similar in cocksfoot and common bent, and significantly higher in meadow fescue. In creeping red fescue (Festuca rubra var. rubra) the combination of CCC at GS 31-32 and Moddus at GS 45-51 gave a higher seed yield increase, on average 41% over the unsprayed control, than the added increase by either PGR given alone. In smooth bromegrass (Bromus inermis), Moddus was effective only when applied at GS 45-51, but the 33% seed yield increase was lower than for application of CCC at GS 31-32. Neither Moddus nor CCC had any significant effect on seed yield in reed canarygrass (Phalaris arundinacea) or smooth meadowgrass (Poa pratensis). Based on these trials, Moddus has now been approved in Norwegian seed production of timothy, meadow fescue, cocksfoot, red fescue, common bent and smooth bromegrass.