ROOTED IN RESEARCH
PRE-PLANT FUMIGATION OPTIONS FOR RENOVATING TURFGRASS SOD FIELDS
By Fred Yelverton, PhD; Travis Gannon, PhD; and Casey Reynolds, PhD
Methyl bromide is a restricted-use pesticide that has long- been the standard for fumigating turfgrass areas before renovation due to its superior efficacy on soil-borne fungi, nematodes, and weeds. However, due to its classification as a Class I ozone-depleting substance, methyl bromide use in turfgrass systems was phased out (
https://www.epa.gov/ ods-phaseout/methyl-bromide) in the first decade of the 21st century.
Due to this phase out, turfgrass managers often rely predominantly on the nonselective herbicide, glyphosate, for bermudagrass eradication. While eradication of difficult perennial weeds such as bermudagrass has been reported, non-fumigation options are lengthy and could require seed or sod fields to be out of use for significant time. For example, in one study three glyphosate applications over 3 months were required for 99 percent control 10 months after treatment. Te time required for glyphosate–bermudagrass eradication can result in significant revenue losses associated with the prolonged re-grassing period and can potentially compromise establishment of subsequent new turfgrasses.
Dazomet is a granular soil fumigant designed to be soil- incorporated by mechanical/physical or water methods. Following incorporation, dazomet reacts with water to produce methyl isothiocyanate, a gas that controls various fungi, insects, nematodes, and weeds. Under favorable conditions, methyl isothiocyanate formation is rapid (dazomet soil half-life <24 h), at which point it can volatilize and escape from the soil profile reducing control. For this reason, management practices such as tarping and tillage are recommended to reduce atmospheric losses. Applicators are recommended to cover treated soil with a plastic tarp, roll it, and/or irrigate to seal fumigant vapors into the soil, which can improve efficacy and reduce off- target movement potential.
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Previous research in northern environments on annual bluegrass (Poa annua) and in southern environments on bermudagrass (Cynodon dactylon sp.) have reported these methods to significantly improve weed control. However, considering implementing such practices comes with additional expenses associated with product costs and labor. Furthermore, tarping and tillage can increase worker exposure and are not feasible in some scenarios. Tese methods can also be extremely impractical and costly in large areas such as seed or sod farms, and as a result, effective, efficient, alternative programs need to be identified.
One option for reducing the amount of time to achieve acceptable control is to pre-treat fumigated areas with single or multiple applications of glyphosate and/or fluazifop. Previous research has shown that applying herbicides before dazomet application can increase long-term control. It has been reported that hybrid bermudagrass control using dazomet may be improved by applying glyphosate 2 weeks before dazomet application. Furthermore, glyphosate improved bermudagrass control during renovations from hybrid bermudagrass to zoysiagrass (Zoysia sp.), as glyphosate followed by dazomet resulted in less bermudagrass (7 percent) than dazomet alone (71 percent) at 15 weeks after establishment. Tis technique was further investigated by researchers at North Carolina State University and Texas A&M University in 2015 to evaluate results for improving difficult perennial weeds prior to turfgrass renovations.
Field experiments were initiated on June 1, 2015, at the NCSU Lake Wheeler Turfgrass Field Laboratory in Raleigh, NC, and on June 22, 2015, at the Texas A&M University Turfgrass Field Laboratory in College Station, TX. Four replications of each treatment were arranged in a randomized complete block design at both locations. Applications of glyphosate (GLY), fluazifop (FLU), and dazomet (DAZ) were applied at various timings and incorporated by irrigation, tillage, and/or rolling as indicated in Table 1.
TPI Turf News March/April 2019
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