A 2-factor experiment was conducted on a USGA-spec. annual bluegrass golf green at NIBIO research station Landvik from August 2016 to May 2018. Factor 1 consisted of two fertiliser programmes: traditional Wallco liquid mineral fertilizer at 2-wk intervals vs. long-lasting Marathon fertilizer at 4-wk intervals. The programmes started on 15 Aug. 2016 and 7 Apr. 2017 and lasted to late October in 2016 and to mid-November in 2017. The total N dose amounted to 207 and 286 kg ha-1 yr-1 in 2016 and 2017, respectively. Factor 2 consisted of four treatments: (i) negative control (no treatment), (ii) positive control (fungicide treatment), (iii) micronutrient mixtures (Melgreen Si and Melgreen Cu) and (iv) combination of (ii) and (iii). The fungicides were applied each time microdochium patch exceeded 2%, in total 3 times in 2016-17 (4 Oct. 2016, 3 Jan. and 23 Feb. 2017) and 2 times in 2017-18 (12 Oct. and 6 Dec. 2017). Disease, overall impression, density and colour were evaluated throughout the growing season at 4-wk intervals prior to Marathon application.
Microdochium patch first appeared in late August 2016 and in mid-September 2017, and the disease was monitored also in winter 2016-17 and 2017-18 as weather conditions allowed. In both years, Marathon significantly improved the colour of the annual bluegrass green, most likely due to a higher iron content in Marathon than in Wallco. In autumn 2017, Marathon also reduced microdochium patch and improved overall impression in spite of lower density on Marathon plots vs. Wallco plots. Marathon can be recommended for use on golf greens instead of Wallco, because of longer fertilisation interval (less labour), better colour and better overall impression. While there was no significant effect of Melgreen Si or Melgreen Cu on microdochium patch, the experiment should be repeated as the annual bluegrass green died in the second winter due to abiotic winter damage.