Proceedings of the Sixty-first Annual Meeting of the Northeastern ...

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AUTUMN PREEMERGENCE AND SPRING POSTEMERGENCE CONTROL OF
MOUSEEAR CHICKWEED AND CRABGRASS IN TURF. P.H. Dernoeden and J. Fu,
Univ. of Maryland, College Park.
ABSTRACT
Mouseear chickweed (Cerastium vulgatum) and smooth crabgrass (Digitaria
ischaemum) are common problematic weeds in Maryland lawns. Preemergence
herbicides were evaluated for control of both weeds in tall fescue (Festuca arundinacea)
and involved single herbicide applications on either 4 November 2005 or 31 March
2006. A postemergence trial also was conducted in April 2006 and targeted primarily
mouseear chickweed, however, there was some corn speedwell (Veronica arvensis)
evenly distributed throughout the study area. In both studies, plots were 5 ft by 5 ft and
arranged in a randomized complete block with four replications. Weed cover was
assessed visually on a 0 to 100% linear scale. Data were subjected to analysis of
variance and significantly different means were separated using Fisher’s LSD at P ≤
0.05. Soil was a Keyport silt loam with a pH of 5.7 to 6.0. Sprayable herbicides were
applied in 50 GPA using a CO 2 pressurized (35 psi) backpack sprayer. Granulars were
applied by shaker bottle. In the preemergence study, mouseear chickweed was
controlled effectively by sprayable formulations of prodiamine 65WG, dithiopyr 40WP
and pendimethalin 3.8CS applied on 4 November (Table 1). Dithiopyr 0.21 G (0.5 lb
ai/A) and prodiamine 0.25G (0.75 lb ai/A) applied 4 November appeared to reduce
mouseear chickweed levels (4.0 to 4.8%) versus the untreated control (10%), but the
difference was not significant. Treatments applied in the spring had little or no effect
since mouseear chickweed had emerged prior to 31 March. Smooth crabgrass
pressure was low and all treatments reduced crabgrass levels significantly when plots
were evaluated 8 September 2006 (Table 1). Highly effective crabgrass control (≤ 2%
crabgrass cover) was provided by dithiopyr 0.21G (0.5 lb ai/A) and prodiamine 65WG
(0.75 lb ai/A) applied 4 November 2005 and dithiopyr 0.21G (0.5 lb ai/A), prodiamine
0.20G (0.5 and 0.75 lb ai/A) and prodiamine 65WG (0.75 lb ai/A) applied 31 March
2006. There were few significant differences in the level of crabgrass control among
herbicide treatments. In the postemergence broadleaf study, the following herbicides
were applied 13 April 2006 to an immature stand of Kentucky bluegrass (Poa pratensis):
quinclorac (0.75 lb ai/A + 1% MSO); 2.4-D + triclopyr (1.5 lb ai/A); triclopyr ester (1.0 lb
ai/A); quinclorac + triclopyr ester (0.5 + 0.5 lb ai/A+1% MSO); and 2.4-D + MCPP +
dicamba + carfentrazone (1.1 lb ai/A; Speedzone). Speedzone exhibited rapid and
effective control of both corn speedwell and mouseear chickweed. All other treatments
were ineffective. Corn speedwell and mouseear chickweed naturally declined and
nearly all plants in untreated plots were dead by 22 May.
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