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

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SAFETY OF POSTEMERGENCE NUTSEDGE-CONTROL HERBICIDES ON
ORNAMENTALS. J.C. Neal, North Carolina State Univ., Raleigh, J.F. Derr, Virginia
Tech, Virginia Beach, and A.F. Senesac, Cornell Cooperative Ext., Riverhead, NY.
ABSTRACT
Several herbicides are labeled for control of nutsedge in turfgrass and other crops;
yet limited options are available for selective postemergence control of yellow nutsedge
and dicot weeds in landscape ornamentals. In cooperation with other researchers
through the USDA IR-4 program, halosulfuron, sulfentrazone and V-10142 were
evaluated for safety on landscape ornamentals. In NC, on 18 April 2006 nine species of
ornamentals were potted into 3-gallon (~12 liter) pots using a pine bark + sand (7:1, v/v)
substrate amended with an industry standard slow-release fertilizer with micronutrients.
Plants in the study were Ilex vomitoria nana, Ilex cornuta burfordii nana, Viburnum tinus
compacta, Liriope muscari variegate, Cotoneaster horizontalis, Spiraea japonica ‘ Little
Princess’, Rhododendron x ‘Pink Gumpo’ (azalea), Abelia x grandiflora ‘John Creech’,
and Lagerstroemia x Tuscarora. Plants were allowed to establish about 8 weeks before
experimental treatments were applied on 28 June and 24 July 2006. In VA, ornamentals
were potted on 8 June 2006 into one-gallon (3-liter) pots. Species included: Spiraea X
Bumalda ‘Gold Mound’, Delosperma cooperi, Salvia elegans ‘Tangerine’, Ophiopogon
japonicus variegata, Cuphea allyson, Pentas lanceolata ‘Ruby Red’, Gardenia
augustofolia radicans, Liriope muscari ‘Aztec’ and Lantana camara ‘Miss Huff’.
Treatments were applied on June 13 th and July 11 th , 2006. In NY, rooted cuttings of
Gypsophila paniculata 'Pink Fairy' (qt container), Rhododendron X 'Crete' (gallon
container), and Rosa x 'Sea Foam' (gallon container) were transplanted into a commercial
soilless media on 8 May, 2006. Spiraea decumbens (gallon container) was transplanted
in April 2006. Treatments were applied on 8 May, 2006 and repeated on 5 June, 2006.
In each study, treatments were applied in randomized complete block designs with 3 pots
of each species per plot and 4 replicates. Halosulfuron DF, sulfentrazone DF (NC only)
and V-10142 were applied over the top of all species using a CO 2 pressurized sprayer
equipped with two flat fan nozzles and calibrated to deliver 30 GPA. Nonionic surfactant
(0.25% v/v) was added to halosulfuron and V-10142 treatments. Sulfentrazone GR was
applied using a hand held shaker jar. Each herbicide was applied at 1x, 2x and 4x the
labeled or suggested use-rate. Halosulfuron caused no injury to Ilex, Azalea, and
Gardenia, but chlorosis and stunting was observed in Spiraea, Liriope, Cotoneaster, and
Viburnum. Significant injury was caused by halosulfuron on Gypsophilia and Rosa, and
Liriope (NC study). Sulfentrazone 4F was safe on Gypsophila but injured Azalea, Spiraea,
Lagerstroemia, Viburnum, Liriope, Cotoneaster and Rosa, although all plants except
Liriope recovered. Spiraea had moderate to slight injury which, by 4WAT of the second
timing, was slight at low rates and moderate at the highest rate. Granular sulfentrazone
was safe on all woody species but injured ice plant and Liriope. V-10142 caused
significant injury to Liriope, Spiraea, Abelia, Cotoneaster, Salvia, ice plant, Mexican
heather and Lantana, but not Ilex or Gardenia. Rhododendron was not injured in NC but
was injured by all rates in the NY study following the second application. These data
suggest that the granular formulation of sulfentrazone has potential for safety to a
diversity of woody ornamentals.
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