Vol. 54—2000 - NorthEastern Weed Science Society

PREEMERGENCE SMOOm CRABGRASS AND BROADLEAF WEED CONTROL IN
MARYLAND, 1998-1999
1.G. Davis, P. H. Dernoeden, and 1. M. Krouse'
ABSTRACT
Three studies were conducted to evaluate herbicides fur preemergence smooth crabgrass
(Digitaria ischoemum [Scbreb.] MuhI.), yellow woodsorrel (Oxalis stricta L.), and spotted
spurge (Euphorbia macuJata L.) control in perennial ryegrass (Lolium perenne L.). Sprayable
herbicides were applied in 50 gpa with a Co, pressurized (35 psi) backpack sprayer equipped
with an 8004E nozzle. GranuIarswere applied using a shakerbottle. All sites were irrigated 24
hrs prior to and after eachherbicide application and thereafter to prevent wihing of the turf. Plots
measured5 by 5 ft. and were arranged in a randomized complete block with four replicates.
Percent of plot area coveted with crabgrass, woodsorrel, and spurge was assessed using a visual
o to 100% linear scale where 0 ~ no weeds and I00 ~ entire plot area coveted with weeds.
Treatments with crabgrass cover ratings exceeding 5% were considered to be commercially
unacceptable. Data were subjected to analyses ofvariance and significantly different means were
separated by the least significant difference test (p ~ 0.05).
In study I, crabgrass pressure was severe, and all treatments reduced smooth crabgrass
cover significantly. Except fur Dimension (dithiopyr) lEC and 0.10 applied at 0.25 Ib ailA, all
other dithiopyr treatments (i.e., 40WP and SC-I02098 2.3 and 2.5 sq, applied at 0.25 and 0.38
lb ailA, and Barricade (prodiamine) 6500 (0.65 lb ailA) provided acceptable crabgrass control.
There were no significant woodsorrel or spurge cover diffurences among the treatments.
In study II, crabgrass pressurewas severe, and all treatments reduced crabgrass cover
significantly (Table 1.). Only Dimension 0.10 (0.38 lb ailA) provided complete control, but
Team Pro (benefm + triflura1in)(1.5 +1.5lb ailA) and TADS 13173 2G (oxadiazon) (4.0 lb ailA)
provided equivalent levels of acceptable crabgrass control, Good control was provided by
pendimetha1in 0.860 (1.5 + 1.5 lb ailA) and TADS 13172 2G (4.0 Ib ailA). All other treatments
provided unacceptable crabgrass control There were few woodsorrel and spurge plants in the
con1rol plots due to competition from the earlier germinating crabgrass. Therefore, data were
analyzedwithoutusing the datafrom the untreatedcontrol, Team Pro (1.5 + 1.5 and 2.0 lb ailA),
and pendimethalin 0.860 (1.5 + 1.5 and 2.0 Ib ailA) provided excellent preemergence
woodsorrel control Plots receiving Dimension O.lG (0.38 lb ailA) were free of woodsorrel
Except fur TADS 13172 2G (2.0 lb ailA), none of the oxadiazon treatments reduced woodsorrel
cover when compared to Team Pro (1.5 + 1.5 and 2.0 lb ailA), pendimethalin 0.860 (1.5 + 1.5
and 2.0 lb ailA), and Dimension lEC (0.25 +0.25 lb ailA). None of the treatments reduced
spurge cover significantly.
Crabgrass pressure in study ill was moderate. Drive (quinclorac) treatments provided
little or no preemergence crabgrass or woodsorrel control (Table 2.). Only Pendulum 3.3EC
(pendimetha1in) (1.5 + 1.5 lb ailA) and Pendulum 2G (1.5 + 1.5 and 3.0 Ib ai/A) provided
acceptable crabgrass and woodsorrel control.
'Graduate research assistant, Professor, and research associate, DepartmentofNatura1 Resource
Sciences and Landscape Architecture, Univ. of Maryland, College Park, Md. 20742.
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