Rolling and Biological Control Products Reduce Microdochium Patch on a Poa Annua Putting Green.

Microdochium patch caused by the pathogen Microdochium nivale is a major turfgrass disease in the Pacific Northwest on annual bluegrass (Poa annua) putting greens. Due to increased pesticide restrictions, there is a desire to manage this disease in the absence of fungicides. The objective of this research was to evaluate the effects of rolling in combination with biological control products on Microdochium patch severity on an annual bluegrass putting green in the absence of traditional fungicides.  A field experiment at the Lewis-Brown Horticulture Farm in Corvallis, OR took place from 26 Sep 2013 to 13 Jun 2014 and again from 22 Sep 2014 to 12 Jun 2015. Experimental design was a 2 by 4 randomized complete split-plot design with four replications. Individual plots were 1.5 m² and the total experimental area was 48 m². Factors included double-rolling applied five days a week compared to a control, and biological control products; Rhapsody (Bacillus subtilis strain WST 713), BW136N (Trichoderma harzianum Rifai strain T-22 + Trichoderma virens strain G-41), and Provide + ReVive (microbe solution containing Bacillus subtilis + a Leonardite derived humic acid) applied every two weeks and compared to a control. Products were applied with a CO₂-powered backpack sprayer at 280 kPa with a carrier volume of 814 L ha^-1. Response variables included area under disease progress curve calculated for the duration of the trial and turfgrass quality (1 to 9 rating) analyzed at the peak of disease (13 Mar 2014 and 18 Feb 2015).  Rolling was shown to be effective at reducing Microdochium patch severity in both years.  Among the biological control products, BW136N provided the most consistent suppression of Microdochium patch followed by Rhapsody.  The ProVide + ReVive combination did not suppress disease in this study.