Rolling plus biological control of Microdochium patch

Microdochium patch (Microdochium nivale) is a major turfgrass disease in cool, humid regions that causes extensive damage to annual bluegrass (Poa annua L.) putting greens in the absence of fungicides. Increasing restrictions on fungicide use and fungicide resistance has sparked interest in finding alternatives to fungicides for managing Microdochium patch. The objectives of this trial were to evaluate the effects of rolling and biological control products on Microdochium patch on an annual bluegrass putting green in the absence of traditional fungicides.

We applied several biological control products at label rates every two weeks from September to June for two consecutive years at the Oregon State University Lewis-Brown Horticulture Farm in Corvallis, Ore. We applied treatments with a backpack sprayer at a rate of 2 gallons of spray solution per 1,000 sq. ft. at 40 psi, and the annual bluegrass putting green was maintained at a 0.150-inch height of cut. In addition to the biological control products, we rolled half of the plots five days a week. We did not apply traditional fungicides from September to June in both years of the study.

Microdochium patch was suppressed by rolling five days a week, and also was suppressed with applications of the biological control products BW136N (consisting of the fungi Trichoderma harzianum Rifai strain T-22 and Trichoderma virens Arx strain G-41) or Rhapsody (consisting of the bacteria Bacillus subtilis strain WST-713). Because of the lack of complete control of Microdochium patch, turf quality was considered unacceptable for putting greens, with rolled treatments in combination with either BW136N or Rhapsody having the highest turf quality rating in both years of the study.

While no treatments provided control comparable to traditional fungicides, future research evaluating rolling or biological control products in rotation or combination with other products such as sulfur or mineral oil may yield more favorable results.