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

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COMPARING SELECTED HERBICIDES TO METHYL BROMIDE FOR WEED
CONTROL IN THREE HERBACEOUS PERENNIALS. D.A. Little, M.W. Marshall,
Michigan State Univ., East Lansing, R.J. Richardson, North Carolina State Univ.,
Raleigh, and B.H. Zandstra, Michigan State Univ., East Lansing.
ABSTRACT
The methyl-bromide (MeBr) phase-out has reduced the ability of ornamental
growers to adequately control weeds. In 2004 and 2005, a field study was conducted at
the Michigan State University Southwest Research and Extension Center located near
Benton Harbor to evaluate herbicides as alternatives to MeBr in nursery production. In
early June 2004, a standard treatment of MeBr:chloropicrin (98:2) was applied at a rate
of 392 kg/ha. Treatments tested were granular flumioxazin (0.28 kg/ha), granular
oxadiazon (2.24 kg/ha), isoxaben (1.12 kg/ha), dithiopyr (0.28 kg/ha), metolachlor (1.68
kg/ha), granular pendimethalin (1.4 kg/ha) plus granular oxadiazon, isoxaben plus
oryzalin, isoxaben plus dithiopyr, isoxaben plus metolachlor, and an untreated control.
Herbicide treatments were applied in mid-June in 2004 and 2005. Perennials evaluated
were bugleweed (Ajuga reptans), periwinkle (Vinca minor), and daylily (Hemerocallis
spp.). Weeds present included common ragweed (Ambrosia artemisiifolia), common
lambsquarters (Chenopodium album), large crabgrass (Digitaria sanguinalis), and
carpetweed (Mollugo verticillata). Crop injury and weed control were visually rated on a
0-100% scale, with 0% equal to no crop injury or no weed control and 100% equal to
complete crop death or weed control. Visual ratings were made monthly for up to four
months. Perennial plant size measurements were collected at the end of each growing
season. Flumioxazin and isoxaben plus oryzalin were the only treatments to provide
better than 60% control of common ragweed, common lambsquarters, large crabgrass,
and carpetweed. However, flumioxazin cause visual injury up to 30, 13, and 23% and
plant size reductions of up to 67, 25, and 20% on bugleweed, periwinkle and daylily,
respectively. Isoxaben plus oryzalin caused visual injury up to 35, 5 and 6% and plant
size reductions of up to 44, 43, and 0% on bugleweed, periwinkle and daylily,
respectively. Isoxaben plus dithiopyr was the only treatment not significantly different
from MeBr across all rating dates for visual injury, plant size, and weed control.
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