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Evaluation of Novel Techniques to Control Annual Grasses in Intensively Managed Turfgrass Systems

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dc.contributor.authorPeppers, John Michaelen
dc.contributor.committeechairAskew, Shawn D.en
dc.contributor.committeememberGoatley, James Michaelen
dc.contributor.committeememberBrown, Philip Jamesen
dc.contributor.committeememberFlessner, Michael L.en
dc.contributor.departmentPlant Pathology, Physiology and Weed Scienceen
dc.date.accessioned2023-12-20T09:00:44Zen
dc.date.available2023-12-20T09:00:44Zen
dc.date.issued2023-12-19en
dc.description.abstractAnnual grassy weeds are problematic in intensively managed turfgrass systems due to a lack of selective and affordable control options. Four projects were conducted from 2020-2023 to evaluate novel techniques for Annual bluegrass (Poa annua L.), goosegrass (Eleusine indica L. Gaertn.), and smooth crabgrass (Digitaria ischaemum Schreb.) control on golf course putting greens or putting green surrounds. Hybrid bermudagrass Cynodon transvaalensis Burtt. Davy. x dactylon L. Pers.) tolerated cumyluron regardless of application timing, endothall when applied during full dormancy, and methiozolin when applied during mid-transition. Methiozolin half-life in the upper 2-cm of 12 hybrid bermudagrass putting greens was approximately 14 days and was prolonged in similar studies by seven orders of magnitude when herbicide was applied to bare ground compared to adjacent Kentucky bluegrass (Poa pratensis L.) turf. In a study conducted in Alabama, California, Florida, and Virginia, methiozolin at labeled use rates applied biweekly controlled smooth crabgrass >80% in creeping bentgrass (Agrostis stolonifera L.) and hybrid bermudagrass turf. Although similar programs also controlled goosegrass, acceptable control required more applications than are allowed on the product label. Targeted application devices (TAD), such as spot sprayers and dabbers that are used for individual plant treatment of escaped weeds, were tested for uniformity of fluid delivery. Fluid output of dabbing devices was highly variable and dependent on reservoir fill level, reservoir air seal, human user, and contact time, but largely independent of peak force exerted during the dabbing event. These studies suggest that new products are available to improve annual grassy weed control in turfgrass systems, but proper application timing and device calibration is important to achieve best results.en
dc.description.abstractgeneralAnnual grasses are difficult to control in "high-end" golf turf because few herbicides can be safely used near greens and key weeds have become resistant to the most common products. Several new products were tested for safety on hybrid bermudagrass greens. Methiozolin (PoaCure) was safe for use after post-dormancy greenup, endothall was safe when used while turf was still dormant, and cumyluron was safe regardless of application timing. The duration of preemergence weed control with methiozolin is reduced as temperatures increase and in turfgrass compared to bare ground systems. Half of the methiozolin product will dissipate in 14 days or less when applied to hybrid bermudagrass putting greens or Kentucky bluegrass lawns in spring. Methiozolin controlled smooth crabgrass for the entire season in several Southeastern states, but goosegrass control was slightly below acceptable levels when the product was used within annual dose restrictions. Applicators, such as dabbers and spot sprayers, that are used to treat individual plants improve turf safety and reduce chemical cost, but these devices had not been previously tested for uniformity of fluid output. Studies found that these devices can vary in output by several orders of magnitude depending on the type of devices used, the person using the device, and duration of contact with the turf as the user presses a dabbing device over a weed. Within-device errors were equally problematic and governed by the amount of downward pressure exerted by the fluid contained in the device reservoir. For every 10% of fluid capacity added, fluid dispense rate increases approximately 33%. When the air seal of the fluid fill cap is broken, fluid output approximately doubles compared to when this seal is maintained because loss of vacuum increases downward force of the fluid column. These studies suggest that new products are available to improve annual grassy weed control in ornamental turf, but proper application timing and device calibration is important to achieve best results.en
dc.description.degreeDoctor of Philosophyen
dc.format.mediumETDen
dc.identifier.othervt_gsexam:39150en
dc.identifier.urihttps://hdl.handle.net/10919/117232en
dc.language.isoenen
dc.publisherVirginia Techen
dc.rightsCreative Commons Attribution 4.0 Internationalen
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en
dc.subjectherbicideen
dc.subjectmethiozolinen
dc.subjectturfgrass weed scienceen
dc.subjectgoosegrassen
dc.subjectsmooth crabgrassen
dc.subjectcreeping bentgrassen
dc.subjecthybrid bermudagrassen
dc.titleEvaluation of Novel Techniques to Control Annual Grasses in Intensively Managed Turfgrass Systemsen
dc.typeDissertationen
thesis.degree.disciplinePlant Pathology, Physiology and Weed Scienceen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.nameDoctor of Philosophyen

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