Research Articles continued
Cover Story
Preemergence Crabgrass Control
with Split versus Single Applications in Tall Fescue Virginia Tech Researchers: Jeffrey F. Derr, Ph.D., Professor of Weed Science, and Adam E. Nichols, Research Assistant, Hampton Roads Agricultural Research and Extension Center, Virginia Beach Sponsors: The Virginia Turfgrass Foundation and The Virginia Agriculture Council
T
hree species of crabgrass can infest turfgrass in Virginia: smooth, large and southern. All three species are summer annuals, starting to germinate generally in mid-March to early April in southeastern Virginia. Although we tend to focus on the onset of crabgrass germination, we must also consider the long germination period for this group of weeds. Our long growing
season in Virginia is beneficial for crop production, but it also allows for extended crabgrass germination. In southeastern Virginia, crabgrass may germinate over a five-month period, from March into August. Most of our crabgrass preventers, however, provide only about three months of control, with late-season germination resulting in crabgrass infestations in July and August. The
use of split herbicide applications may address the mid- to late-germination period.
Our research
Our trials compared Tenacity (mesotrione), Barricade (prodiamine), Pendulum AquaCap (pendimethalin) and Dimension (dithiopyr) applied in single versus split applications. We applied each product at what we
Table 1. Preemergence crabgrass control in tall fescue with single and split applications in 2011.
SOUTHERN CRABGRASS COVER Treatment
Rate in lb. ai/A
Untreated
6/20/11 103 DAT 40 DAT2
7/19/11 132 DAT 69 DAT2
9/8/11 183 DAT 120 DAT2
2%
21%
84%
Tenacity
0.125
5%
33%
77%
Tenacity
0.25
5%
40%
91%
Tenacity + Tenacity
0.125 0.125
3%
35%
75%
Barricade 65 WDG
0.75
0%
1%
2%
Barricade + Barricade 65 WDG
0.38 0.38
0%
0%
2%
Pendulum AquaCap
3.0
0%
3%
29%
Pendulum AquaCap + Pendulum AquaCap
1.5 1.5
0%
0%
7%
Dimension 2EW
0.5
1%
9%
35%
Dimension 2EW + Dimension 2EW
0.25 0.25
0%
1%
23%
1
16
21
LSD (P=.05)
DAT = days after the first application DAT2 = days after the second application (for the split application treatments) 20 | Virginia Turfgrass Journal May/June 2012 www.vaturf.org