The main objective of this project was to provide documentation for potential registration of Primo maxx® for use on Nordic golf courses. The project started in 2007 with trials according to Good Experimental Practice standard at Landvik, Norway and Lepaa, Finland. Primo maxx® was applied at monthly rates varying from 0.2 to 0.8 l ha-1 on greens and 0.5 to 3.0 l ha-1 on fairways. These treatments resulted in average clipping yield reductions of 18% on bluegrass/fescue fairways and 21% on creeping bentgrass greens. Growth suppression during the first two weeks after application was often followed by a rebound effect during the remaining two weeks until next application. While significant losses in turfgrass quality occurred at rates of 1.0 l ha-1 and higher in the fairway trial at Landvik, monthly applications of at least 1.5 l ha-1 ha resulted in less snow mould (Microdochium nivale) and faster spring green-up in 2008 in the fairway trial at Lepaa.
Because of the discoloration and rebound effects in 2007, Primo maxx® was applied at lower rates but higher frequencies in new trials established in 2008. In a green trial at Landvik, weekly or biweekly applications of 0.15, 0.30 and 0.45 l ha-1 were compared with an unsprayed control area. On average for application rates and frequencies, Primo maxx® had no effect on turfgrass overall appearance or density but reduced clipping yield by 25% and increased ball roll distance by 6%. In a new fairway trial at Lepaa, biweekly applications of 0.4, 0.8, 1.2 and 1.6 l ha-1 had no effect on turfgrass quality but reduced clipping yields by 15, 23, 23 and 34%, respectively. Rebound effects were virtually absent in the 2008 trials. Spring observations in Finland in 2009 confirmed that there was less snow mould and better overall appearance on plots that had been sprayed with Primo maxx® in 2008. In conclusion, we have recommended that Primo maxx® be labelled for use on Nordic golf courses at the following rates and application frequencies:
Rate* Application interval:
Greens:
(creeping bentgrass) 0.2 – 0.4 L ha-1 Every 1 to 2 weeks.
Fairways:
(Kentucky bluegrass / red fescue) 0.6 – 1.2 L ha-1 Every 2 to 3 weeks.
Roughs & semi-roughs:
(Kentucky bluegrass / red fescue) 1.0 – 2.0 L ha-1 Every 3 to 4 weeks.
*Always use lowest rate for the first seasonal application of Primo maxx®.
As of 1 January 2010, Primo maxx® has been approved for turfgrass use in Iceland. Applications are pending in Finland, Sweden and Norway.
