control options are currently limited for dallisgrass. One of the most common control programs is the use of sequential monosodium methanearsonate (MSMA) applications; however, this may present phytotoxicity concerns to warm-season turfgrasses (Henry et al
Christopher R. Johnston and Gerald M. Henry
Susan L.F. Meyer, Inga A. Zasada, Shannon M. Rupprecht, Mark J. VanGessel, Cerruti R.R. Hooks, Matthew J. Morra, and Kathryne L. Everts
, including timing and rates of application ( Meyer et al., 2011 ; Rothlisberger et al., 2012 ; Snyder et al., 2009 ). Because of potential phytotoxicity, application of mustard seed meals as biofumigants must be timed to avoid phytotoxicity to crop plants
Victoria J. Ackroyd and Mathieu Ngouajio
control soilborne pathogens, while contributing other benefits such as decreased erosion and weed suppression. Research suggests that brassica cover crops may be phytotoxic to cash crop seeds. Haramoto and Gallandt (2005) determined that brassica cover
David A. Bender, J. Wayne Keeling, and Roland E. Roberts
Large weeds, particularly amaranths, are a serious impediment to mechanical harvesting of jalapeno peppers. Several herbicides were applied in 1998 and 1999 postemergence topical (PT) to commercial fields when peppers had four to six leaves, or postdirected (PD) with a shielded sprayer ≈1 month later, and evaluated for crop injury, weed control, and effects on yield. Treatments were applied to four-row plots 9 m long with a CO<subscript>2 backpack sprayer. PT treatments included pyrithiobac sodium at 0.036, 0.053, or 0.071 kg·ha–1 a.i. with nonionic surfactant or crop oil concentrate, metolachlor at 1.68 kg·ha–1 a.i., and oxyfluorfen at 0.14 or 0.28 kg·ha–1 a.i.. PD treatments consisted of the same rates of pyrithiobac sodium with nonionic surfactant only, and the same rates of oxyfluorfen. Pyrithiobac sodium PT caused significant chlorosis (reduction in SPAD chlorophyll) in new foliage and reduction in plant height after 1 week, but plants recovered with no effect on final plant height, chlorophyll, or yield. No significant difference was observed between the two adjuvants. Metolachlor had no measurable effect on pepper growth or yield. Oxyfluorfen PT killed young apical tissue and caused chlorosis of immature leaves. Plants recovered, but plant height was reduced by 14% to 28% and yield by 11% to 43%. PD treatments had no effect on pepper growth or yield. All herbicides provided adequate weed control under light pressure. Pyrithiobac sodium appears to have potential as a postemergence herbicide for control of amaranth in jalapeno peppers.
J.G. Norcini and J.H. Aldrich
Eight species of low-growing woody and herbaceous landscape plants were evaluated for tolerance to 1.1 or 2.2 kg a.i. bentazon/ha (plus a crop oil) applied over the top twice 7 days apart. Raphiolepis indica L. Lindl. `Alba' was the only species tolerant to bentazon in either of two experiments. Bentazon injury to Liriope muscari (Decne.) L.H. Bailey `Evergreen Giant' was minor (slight chlorosis) and would probably be tolerable under most landscape situations. Injury (primarily chlorosis/necrosis) to Carissa macrocarpa `Emerald Blanket', Juniperus horizontalis Moench `Bar Harbor', Pittosporum tobira (Thunb.) Ait. `Compacta Green', Trachelospermum asiaticum (Sie-bold & Zucc.) Nakai `Aslo', Ophiopogon japonicus (Thunb.) Ker-Gawl., and Hemerocallis × `Aztec Gold' was significant and therefore unacceptable. Chemical name used: 3-isopropyl-1H-2,1,3-benzothiadiazin-(4)-3H-one 2,2-dioxide (bentazon).
John F. Karlik and Martha P. Gonzalez
Roses are likely the most popular garden plant in the United States, and cultivars are also used as landscape plant materials. Three herbicide trials with two main objectives were conducted with rose plants. The first objective was to evaluate injury to the roses when over-sprayed at various stages of growth. The second objective was to evaluate the efficacy of the herbicides. All herbicides were used at label rates and applied over the top of rose plants. In the first trial, the pre-emergent herbicides pendimethalin, oryzalin, trifluralin, metolachlor, napropamide, and oxyfluorfen were applied to plots containing dormant roses with ≈1-cm shoots just pushing. Evaluations of shoot length taken over the next 6 weeks showed no differences in growth of rose plants, but weed populations were reduced. In the second trial, five post-emergent herbicides were applied to plots containing dormant roses. Herbicides evaluated included the grass herbicides fluazifop-p-butyl, sethoxydim, and clethodim. The nonselective herbicide glyphosate was included in the trial, as was a combination herbicide containing 2,4-D, mecoprop, and dicamba. There was no visible injury to rose plants until 6 weeks after treatment. At that time, roses treated with glyphosate had shorter shoots. Recovery from glyphosate appeared more rapidly than recovery from the combination herbicide. Weed control varied with each herbicide. The third trial evaluated the same five herbicides for control of bermudagrass in late spring. Injury to roses was noted immediately from the combination herbicide and glyphosate. All the grass herbicides and glyphosate were effective in controlling bermudagrass.
Sang Ryul Shim and B.J. Johnson
Creeping bentgrass (Agrostis palustris Huds.) putting greens are commonly infested with crabgrass (Digitaria spp.) and goosegrass [Eleusine india (L.) Gaertn.]; however, many herbicides have the potential to severely injure this turfgrass species. A field investigation was conducted over 2 years to determine the tolerance of creeping bentgrass to various herbicides. Trifluralin plus benefin (2.2 to 6.7 kg·ha-1), dithiopyr (0.37 to 1.1 kg·ha-1), and prodiamine (0.5 to 1.7 kg·ha-1) did not injure creeping bentgrass. Pendimethalin caused only slight injury when applied at 3.4 kg·ha-1, but injury increased in 1 of 2 years when applied at ≥6.7 kg·ha-1. Creeping bentgrass was severely injured when treated with benefin plus oryzalin (≥4.5 kg·ha-1), fenoxaprop (0.07 kg·ha-1), and oxadiazon (3.4 kg·ha-1) granular and WP formulations and, therefore, should not be applied to the turf. Chemical names used: N -butyl-N -ethyl-2, 6-dinitro-4-(trifluoromethyl) benzenamine (benefin); S,S -dimethyl 2-(difluoromethyl-4-(2-methylpropyl)-6-(trifluoromethyl-3, 5-pyridinedicarbothioate (dithiopyr); (±) 2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic acid (fenoxaprop); 4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin); 3-[2,4-dichloro-5-(l-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one (oxadiazon); N -(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine (pendimethalin); 2,4-dinitro N,N -dipropyl-6-(trifluoromethyl)-1,3-benzenediamine (prodiamine); 2,6-dinitro-N-N -dipropyl-4-(trifluoromethyl)benzenamine (trifluralin).
Charles L. Webber III, Merritt J. Taylor, and James W. Shrefler
the second application date, 21 July 2010 and 2011. Because of the delayed emergence of yellow nutsedge, only one application of PA was received by the weed. Weed-control and crop injury (phytotoxicity) ratings were collected at 1, 3, 7, 9, 11, 16, 22
Charles L. Webber III, Merritt J. Taylor, and James W. Shrefler
cutleaf groundcherry and spiny amaranth represented 35% and 3% of weed cover, respectively. Yellow nutsedge represented less than 2% of the weed cover. Weed control and crop phytotoxicity ratings were collected at 1, 3, 7, 9, 11, 16, 21, and 28 DAIT (17
B.R. Bondada, R Romero-Aranda, J. Syvertsen, and L. Albrigo
Foliar applications of urea-nitrogen are widely used to alleviate N deficiencies in citrus; however, improper applications can cause serious foliar burn and loss of active green leaf area. Light (LM), transmission (TEM), and scanning (SEM) electron microscopy were used to characterize anatomical and ultrastructural details of foliar burn in citrus. LM examination of the burned leaf area showed collapsed adaxial and abaxial epidermal cells and plasmolysis of mesophyll cells that created large intercellular spaces. SEM showed wrinkling of both the adaxial and abaxial epidermal cells. TEM revealed cytoplasmic vacuolation, disruption of cellular membrane, degradation of grana, and appearance of large plastoglobuli, implying loss of physiological activity. In contrast, control leaves had turgid adaxial and abaxial epidermal cells and compact mesophyll cells with few intercellular air spaces.