Vol. 54—2000 - NorthEastern Weed Science Society

TOLERANCE OF ORNAMENTAL GROUNDCOVER SPECIES TO
POSTEMERGENCE APPLICATIONS OF CLOPYRALID
A. F. Senesac', L. J. Kuhns and T. L. Harpster"
ABSTRACT
In 1999, two studies were conducted at the Long Island Horticultural Research
and Education Center (L1HREC), Riverhead NY and the Penn State University
Horticulture Farm (PSUHF) at Rock Springs, PA to determine the tolerance of
various ornamental groundcovers to the herbicide clopyralld (Lontrel).
Treatments consisted of three rates of clopyralid (0.25, 0.5 and 1.0 Ib.lac.) and
an untreated control. Treatments were applied twice 30 days apart during the
growing season. English ivy (Hedera helix), pachysandra (Pachysandra
tenninalis) and vinca (Vinca minot) were tested at both sites. A decrease in dry
weights was observed for ivy at all treatment rates at both sites. Dry weight
decreased for vinca only at the L1HRECsite at the highest rate of c1opyralid. For
pachysandra, no effect on dry weight was observed.
Eight addltional species were tested at the L1HREC site including bugleweed
(Ajuga reptans 'Burgundy Glow'), daylily (Hemerocaflis 'Burning Daylight'),
gazania (Gazania rigans 'Daybreak Mix'), hosta fortunei (Hosta fortunei 'Aureomarginata'),
hosta siebold (H. siebold 'Elegans'), rosemary (Rosmarinus
officinalis 'Prostratus'), sedum (Sedum spurium 'Dragon's Blood Tncolor'), and
veronica (Veronica peduncularis 'Georgia Blue'). Dry weights did not significantly
decrease for treated samples of rosemary, veronica, ajuga, and daylily. Dry
weights decreased for gazania, hosta fortunei, and sedum at all rates and for
hosta siebold at the two higher rates.
'Weed Science Specialist, Cornell Cooperative Extension, Long Island
Horticuttural Research and Extension Center, Riverhead, NY 11901
2Professorand Research Associate,The PennsylvaniaState University,
Universfty Park, PA 16802
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