An Integrated Nutritional and Chemical Approach to Poa Annua Suppression in Creeping Bentgrass Greens

Abstract

Creeping bentgrass (Agrostis stolonifera L.) provides an ideal putting surface for golf courses located in temperate climates but is invaded by annual bluegrass (Poa annua L.) and silvery‐thread moss (Bryum argenteum Hedw.). There are no currently registered herbicides for annual bluegrass control in bentgrass greens. Paclobutrazol and FeSO4 will suppress one or both of these pests, but research on the effectiveness of the two together has not been reported. Our objectives were to determine the effects of repeated high rates of FeSO4 and paclobutrazol on transitioning annual bluegrass out of a creeping bentgrass green and determine if seaweed extract (SWE) aids the transition. An unanticipated objective was to assess treatment effects on moss incidence. The effects of all combinations of FeSO4 (0.0, 12.2, 24.4, or 48.8 kg ha−1), paclobutrazol (0.18–0.36 kg a.i. ha−1), and SWE (12.8 L ha−1) on control of these pests were investigated over 2 yr on a ‘Penneagle’ green. All FeSO4 rates decreased annual bluegrass to 21% when averaged over 2 yr. The paclobutrazol program reduced annual bluegrass to 5% regardless of FeSO4 rate. Repeated use of SWE had no effect on annual bluegrass or moss populations. An 8% decline in annual bluegrass occurred in untreated plots, possibly due to creeping bentgrass competition being favored by biweekly application of ammonium sulfate and exclusion of phosphorus and potassium fertilizers. Treatment with FeSO4 decreased moss, regardless of paclobutrazol or SWE. Paclobutrazol increased moss when FeSO4 was not applied. Season‐long applications of FeSO4 (24.4 kg ha−1) plus high rates of paclobutrazol controlled annual bluegrass and silvery‐thread moss while providing a putting surface of acceptable quality.

Suppression of Annual Bluegrass in Creeping Bentgrass Putting Greens Using Plant Growth Regulators

“…It was previously shown that maximum or even higher than recommended PGR rates were the most effective for annual bluegrass suppression (Woosley et al, 2003). Ervin et al (2017) tested PB rates higher than those on the label in programs to eradicate Table 4. Impact of flurprimidol (FP), paclobutrazol (PB), and trinexapac-ethyl (TE) plant growth regulators applied at various rates as standalone products or two-way (FPDTE) and/or three-way (FPDPBDTE) mixtures (as described in Table 2) on average annual bluegrass cover and average creeping bentgrass injury (10 = highest) in 2017-19 at Bel-Air Country Club, Los Angeles, CA.…”

“…The authors also suggested that the main factor contributing to the observed damage was the occurrence of low temperatures, which was only a minor issue in our study. Ervin et al (2017) observed both effective control of annual bluegrass and voids in the turf canopy due to the use of an aggressive PB program. Although it was not an issue in our trial, such a risk should also be considered when using PGRs.…”

“…Furthermore, PB standalone treatments in their study had comparable or improved quality when compared with the untreated control. Ervin et al (2017) reported that PB treatments typically resulted in superior turf quality when compared with the untreated control. However, the authors perceived the incidence of reduced quality with PB during a few rating events in late spring and late fall, and they concluded that this might have been an indicator of phytotoxicity.…”

Long-Term Efficacy of Annual Bluegrass Control Strategies on Golf Course Putting Greens

“…However, Ervin et al (2017) reported a decrease in ABG in Virginia from iron applications when N was 3.0 lb N/1000 sq ft/yr. The decrease in ABG reported by Ervin et al (2017) may be due to the 14‐day application frequency used compared with the 28‐day interval in our study. Xu and Mancino (2001) observed in the greenhouse that high application rates of Fe were more injurious to ABG than creeping bentgrass.…”

“…Applications of iron sulfate or “ferrous sulfate” (FeSO 4 · 7H 2 O) fertilizer reduced populations of ABG in full sun (Bell et al, 1999; Ervin et al, 2017; Han et al, 2017) but not in shaded conditions where iron applications encouraged ABG (Stiegler et al, 2003). Further investigation comparing plant growth regulator (PGR) and herbicides with treatments of FeSO 4 will help provide insight on nutritional approaches to ABG control in addition to conventional PGR and herbicide approaches.…”