Evaluation of Organic Amendments and Delivery Technologies for Control of Large Patch Disease (Rhizoctonia solani) on Zoysiagrass (Zoysia japonica) Fairways.

Organic amendments may suppress soil-borne pathogens by increasing soil microbial population density and activity, which subsequently suppress fungal disease by antagonism, parasitism, or competition. This experiment aimed to determine if organic amendments, including an animal waste-based product (AW), a sewage-based organic N fertilizer, and a plant byproduct could suppress large patch caused by Rhizoctonia solani on zoysiagrass (Zoysia japonica). Other treatments included a synthetic N fertilizer, a synthetic fungicide (a.i. azoxystrobin), and an nontreated control (NC). All treatments were applied on a zoysiagrass fairway either as topdressing or topdressing following aerification twice a year for two years. Disease severity, measured by area under the disease progress curve (AUDPC) over the two-year period, indicated that AW reduced disease severity up to 49% compared to NC.  None of other organic amendments reduced large patch compared to NC. Amendments applied resulted in a shift of the soil bacterial community as measured by gram positive to gram negative bacteria (G+/G–) ratio. Compared to topdressing, aerification resulted in lower fungi, fungi to bacteria (F/B) ratio and stress indicators, creating an environment which favors bacteria but not fungi. The suppression of large patch in AW-treated plots may be associated with the reduced G+/G– ratio.