Emergence and Growth of Tall Fescue Seedlings after Postemergence Broadleaf Herbicide Application

Effective weed control prior to seeding is essential for proper turfgrass establishment since competition from weeds can cause sward establishment to fail. Herbicides with multiple active ingredients from different chemical families could increase weed control efficacy, but hinder the establishment of newly seeded turf. Research trials were initiated in the fall of 2020 in Olathe and Manhattan, KS, to determine if tall fescue (Schedonorus arundinaceus) could be seeded earlier after application than stated on the herbicide labels. Overall, this study demonstrated that seeding between 0 to 14 days after an application of carfentrazone-ethyl + MCPP + 2,4-D + dicamba (SpeedZone), fluroxypyr + halauxifen-methyl + 2,4-D Choline (GameOn); or triclopyr + pyraflufen-ethyl + 2,4-D + dicamba (4-Speed XT) had little or no effect on tall fescue growth under the conditions evaluated in these experiments. In general, herbicide manufacturers must consider altering label reseeding intervals before using the results reported herein as guidelines.


Emergence and Growth of Tall Fescue Seedlings after Postemergence Broadleaf Emergence and Growth of Tall Fescue Seedlings after Postemergence Broadleaf Herbicide Application Herbicide Application Abstract Abstract
Effective weed control prior to seeding is essential for proper turfgrass establishment since competition from weeds can cause sward establishment to fail. Herbicides with multiple active ingredients from different chemical families could increase weed control efficacy, but hinder the establishment of newly seeded turf. Research trials were initiated in the fall of 2020 in Olathe and Manhattan, KS, to determine if tall fescue (Schedonorus arundinaceus) could be seeded earlier after application than stated on the herbicide labels. Overall, this study demonstrated that seeding between 0 to 14 days after an application of carfentrazone-ethyl + MCPP + 2,4-D + dicamba (SpeedZone), fluroxypyr + halauxifen-methyl + 2,4-D Choline (GameOn); or triclopyr + pyraflufen-ethyl + 2,4-D + dicamba (4-Speed XT) had little or no effect on tall fescue growth under the conditions evaluated in these experiments. In general, herbicide manufacturers must consider altering label reseeding intervals before using the results reported herein as guidelines.

Summary
Effective weed control prior to seeding is essential for proper turfgrass establishment since competition from weeds can cause sward establishment to fail. Herbicides with multiple active ingredients from different chemical families could increase weed control efficacy, but hinder the establishment of newly seeded turf. Research trials were initiated in the fall of 2020 in Olathe and Manhattan, KS, to determine if tall fescue (Schedonorus arundinaceus) could be seeded earlier after application than stated on the herbicide labels. Overall, this study demonstrated that seeding between 0 to 14 days after an application of carfentrazone-ethyl + MCPP + 2,4-D + dicamba (SpeedZone), fluroxypyr + halauxifen-methyl + 2,4-D Choline (GameOn); or triclopyr + pyraflufen-ethyl + 2,4-D + dicamba (4-Speed XT) had little or no effect on tall fescue growth under the conditions evaluated in these experiments. In general, herbicide manufacturers must consider altering label reseeding intervals before using the results reported herein as guidelines.

Rationale
Herbicides are a vital component to weed management in turfgrass; however, limited research exists on chemical weed control at the seedling stage despite the common practice of reseeding immediately after herbicide application. The introduction of new combination products raises concerns regarding the delay in seeding required after application.

Objective
The objective of this research was to determine the influence of combination products used for postemergence control of broadleaf weeds on emergence and growth of tall fescue seeded between 0 and 14 days after application.

Study Description
Field experiments were initiated in the fall of 2020 in Olathe and Manhattan, KS, to determine if tall fescue could be seeded into a stand between 0 to 14 days after herbicide application. The experiments were arranged in a two-way factorial, randomized complete block design with four replicates. Treatments were five herbicides (noted below) and four seeding intervals (0, 3, 7, and 14 days after herbicide application). Herbicides consisted of a nontreated control; SpeedZone; GameOn; 4-Speed XT; and penoxsulam + sulfentrazone + 2,4-D + dicamba (Avenue South). Each herbicide was applied to the trial area at its highest label rate recommended for cool-season turfgrasses. All treatments were applied using a CO 2 -pressurized, handheld spray boom sprayer equipped with four TeeJet8003 flat-fan nozzles on 9.8-inch spacing calibrated to delivery 43 gal/a. Coverage of all plots was visually rated weekly using a scale of 0 to 100% cover (0% = no visible coverage; 100% = full coverage of plot). A handheld normalized difference vegetation index (NDVI) meter was used to record measurements at 21, 28, 42, and 56 days after seeding. Turf canopy height (inches) was measured 42 DAT (days after herbicide treatment). All data for each of the ratings were subjected to ANOVA in SAS (v. 9.4, SAS Institute Inc., Cary, NC) using the GLIMMIX procedure and means were separated according to Fisher's Protected LSD.

Results
The herbicide treatment main effect was significant for tall fescue cover, NDVI, and canopy height, but seeding interval was not impactful. At the Manhattan site, tall fescue visual cover was reduced in Avenue South-treated plots compared to nontreated soil. No other herbicide treatment reduced cover compared to the nontreated; all had ≥ 94% visual cover. At the Olathe site, no herbicide treatment affected tall fescue cover compared to nontreated tall fescue. Canopy height and NDVI measurements were significantly lower in Avenue South-treated plots at both study sites when compared to nontreated turf. At either site, no other herbicide treatment reduced canopy height or NDVI measurements compared to nontreated tall fescue.

Kansas State University Agricultural Experiment Station and Cooperative Extension Service
Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. Persons using such products assume responsibility for their use in accordance with current label directions of the manufacturer.   Herbicides were applied on August 24, 2020 (Olathe, KS) and September 2, 2020 (Manhattan, KS). Tall fescue was seeded at 0, 3, 7, and 14 DAT. c Means followed by the same lowercase letter in a column are not significantly different according to Fisher's LSD (P ≤ 0.05). Means are averages over seeding intervals, n = 16.