Evaluation of Preemergent Weed Control of Phoma Macrostoma in Bermudagrass.

Effective natural options for weed control in turfgrass systems have been limited.  Phoma macrostoma is a fungus being developed as a natural herbicide for selective broadleaf weed control.  The solid fermentation of P. macrostoma on grain produces a product that is applied as a dry granule.  Herbicidal activity from this product causes foliar bleaching and necrosis of susceptible broadleaf weeds.  Previous research with this product is limited to cool-season climates, and information is limited on appropriate application rates or efficacy at higher temperatures and weeds associated with warm-season turf.  Spectrum of weed control is still being explored, most recently in Texas.  Preemergent field studies were carried out in College Station and Huntsville, TX locations in the fall of 2012 to evaluate preemergent characteristics of various application rates of P. macrostoma compared to corn gluten meal (CGM) and pendimethalin. Studies were conducted on irrigated stands of ‘Riviera’ and ‘Tifway’ bermudagrass.  Selected weeds were seeded into treated plots, with dandelion and common chickweed germinating the best.  In College Station the highest application rate resulted in 50% fewer total weeds than the untreated and fewer total weeds compared to CGM.  All rates of P. macrostoma controlled dandelion for the duration of the trial, with the highest two rates providing 100% control 78 days after treatment (DAT).  Though not significantly different, the highest rate of P. macrostoma resulted in 50% less common chickweed compared to CGM.  Similar results were seen in Huntsville, with all P. macrostoma rates providing 100% control of dandelion 105 DAT.  While P. macrostoma generally provided superior preemergent control to CGM, it did not provide the same level of control as pendimethalin.