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Michele Bigger and Hannah M. Mathers

A limiting factor in container production is cold temperature. Young roots have been found to be less hardy than mature roots (Steponkus, 1976; Studer et al., 1978). Proper overwintering procedures are essential to assure a viable crop in the spring. A common overwintering practice is the application of a preemergent dinitroanaline (DNA) herbicide prior to covering. The objectives of this research were to: 1) determine young and mature root hardiness values for containerized plants that did and did receive DNA herbicides prior to overwintering; 2) investigate differences in regrowth potential between untreated and DNA herbicide treated containers 30, 60, and 180 days after freezing (DAF). Research began in June 2003 and concluded Mar. 2004. In Aug. and Oct. 2003, herbicide treatments of 1× oryzalin (2.0 lb/acre a.i.), prodiamine (2.0 lb/acre a.i.), pendimethalin (3.0 lb/acre a.i.), trifluralin (2.0 lb/acre a.i.), or no treatment (control) was applied to the plants. In Jan. or Mar. 2004, plants were frozen to temperature treatments of, 0, –5, –10, –15, or –20 °C. After freezing, they were placed in a heated greenhouse and evaluated for regrowth. Regrowth and hardiness were evaluated two ways: by a visual rating score (0-10), where 0 = dead and 10 = healthy; and plant live height. Results pooled over all species, temperatures, sampling dates at 30 DAF show prodiamine significantly increased hardiness (23.7%) compared to the control. Results pooled over all species, temperatures, sampling dates, and all DAF show prodiamine significantly increased regrowth potential (24.5%) compared to the control. Both sampling date and DAF were significant when pooling over all species, temperatures, and herbicide treatments, indicating root injury had occurred.

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Edmund J. Ogbuchiekwe and Milton E. McGiffen Jr.

Economic analyses compared the returns of weed control methods for drip and sprinkler irrigated celery (Apium graveolens L. `Sonora'). The nine treatments included an untreated control, cultivation as needed for weed control, a pre-emergent herbicide (trifluralin), and six post-emergent herbicides. The effect of each treatment on weed control, yield, crop value, cost of control, costs for additional hand-weeding, net return, and dollar investment (marginal rate of return) was determined. The treatments that reduced weed populations under drip and sprinkler irrigation also increased yield, net returns, and rate of returns. Effective weed control reduced the additional costs of hand-hoeing the weeds not killed by herbicides, resulting in greater net return. The net returns of weed control were even greater when celery was drip irrigated than when sprinklers were used. In 1998, the sprinkler irrigated field returned $1148 to $3921/ha, compared with -$5984 for the untreated control. Net returns for drip irrigation were much higher, ranging from $3904 to $9187/ha compared with -$8320 for the untreated control. Net returns were also higher in 1999, ranging from $2466 to $5389 when weeds were controlled compared with a net loss of $5710 for the untreated control in the sprinkler irrigated field. The returns on the drip-irrigated field were much higher, from $6481 to $8920 when weeds were controlled, compared with -$8046 for the untreated control. The associated returns for every dollar invested (marginal rate of return) in the non-dominated treatment (more return and lower cost) ranged from 52% to 156% for sprinkler irrigation, and 59% to 144% for drip irrigation in 1998. In 1999, the rate of return for each dollar invested ranged from 104% to 324% for sprinkler and 2.4% to 321% for drip irrigated fields.

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Richard G. Greenland

Few herbicides are available for weed control in carrot. Many of those that are available are old and are in danger of being discontinued. From 2000–04, field experiments were conducted on sandy loam soils at the Oakes Irrigation Research Site in North Dakota to evaluate some of the newer herbicides for possible use in carrot production. Herbicides were tested with preplant incorporated (PPI), preemergence (PRE), and/or several postemergence (POST) application timings. The major weed in this study was hairy nightshade. Cloransulam applied PRE severely injured carrot. Dimethenamid reduced carrot stand and isoxaflutole injured carrots when they were applied PRE. Neither controlled hairy nightshade when applied either PRE or POST, resulting in carrot yield reductions. Acetochlor reduced carrot stand when applied PRE and did not control hairy nightshade when applied either PPI or PRE, resulting in reduced carrot yield. Mesotrione killed carrots when it was applied PRE, but only slightly injured carrots when applied POST. Carrot yield was reduced in some years due to lack of hairy nightshade control when mesotrione was applied POST. Sulfentrazone reduced carrot stand and yield when applied PRE. It was less injurious to carrots when applied POST, but carrot yields were reduced in some years due to lack of hairy nightshade control. Flumioxazin severely reduced carrot stand when applied PRE. When it was applied after carrots were 8 cm tall, it slightly injured carrots, but did not reduce yield except in one year when it did not control hairy nightshade. None of the herbicides tested did consistently as well as the old standards of linuron, DCPA, and trifluralin, but flumoixazin, sulfentrazone, and mesotrione may hold some promise if applied POST.

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Larry A. Rupp, William A. Varga and Roger Kjelgren

Bigtoothmaple(Acer grandidentatum Nutt.) is of interest for its fall color and potential use in water-conserving landscapes. Clonal propagation of desirable selections would be beneficial. Since bigtooth maple commonly self-propagates by layering, we explored mound layering as a means of vegetative propagation. A stool bed was established in 1999 with seedlings grown from northern Utah seed. Beginning in 2001, seedlings were dormant pruned to their base and shoots allowed to grow until early July, when treatments were applied. At the time of treatment application for the reported experiments, shoot bases were girdled with 24-gauge copper wire, covered with conifer wood shavings, and kept moist during the growing season. The effects of rooting hormones and enclosure of the rooting environment on rooting were examined. On 7 July 2002, 32 trees were randomly selected and the four tallest shoots within each tree were treated with either 0, 1:5, 1:10, or 1:20 (v/v) solutions of Dip-N-Gro© rooting hormone (1% IBA, 0.5% NAA, boron). There was no significant difference in rooted shoots between treatments and 81% of the trees had at least one rooted shoot. On 9 July 2004, 39 trees were selected and two shoots per tree were girdled. One-half of the stool bed area was treated by underlaying the shavings with BioBarrier© (17.5% trifluralin a.i.). Measurements on 12 Nov. 2004 showed no apparent treatment effect on rooting and 90% of the trees had at least one rooted shoot. This research demonstrates that mound layering is an effective means of rooting shoots of juvenile bigtooth maples. Further research will examine the effectiveness of the technique in propagating mature clones.

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Glenn B. Fain, Charles H. Gilliam and Gary J. Keever

Hardy ferns are widely grown for use in the landscape. Studies were conducted to evaluate the tolerance of variegated leatherleaf fern (Arachniodes simplicor `Variegata'), tassel fern (Polystichum polyblepharum), autumn fern (Dryopteris erythrosora), holly fern (Cyrtomium falcatum `Rochfordii'), and southern shield fern (Dryopteris ludoviciana), to applications of selected preemergence applied herbicides. Liquid applied herbicides were pendamethalin (LPM) at 3.36 or 6.73 kg·ha–1, prodiamine (LPD) at 1.12 or 2.24 kg·ha–1, isoxaben (LIB) at 1.12 or 2.24 kg·ha–1, and the combination of prodiamine plus isoxaben (LPI) at 1.12 plus 1.12 kg·ha–1. Granular applied herbicides were pendamethalin (GPM) at 3.36 or 6.73 kg·ha–1, prodiamine (GPD)1.12 or 2.24 kg·ha–1, oxadiazon plus prodiamine (GOP) at 1.12 + 0.22 or 2.24 + 0.44 kg·ha–1, oxyfuorfen plus oryzalin (GOO) at 2.24 + 1.12 or 4.48 + 2.24 kg·ha–1, trifluralin plus isoxaben (GTI) at 2.24 + 0.56 or 4.48 + 1.12 kg·ha–1, oxadiazon (GO) at 4.48 or 8.97 kg·ha–1, and oxadiazon plus pendamethalin (GOPD) at 2.24 + 1.4 or 4.48 + 2.8 kg·ha–1. The greatest reduction in growth of autumn fern was observed with GOPD, GO, and GOP; all three containing oxadiazon as an active ingredient. Reductions in holly fern growth were most severe when plants were treated with GTI resulting in a 42% and 54% decrease in frond length and frond number, respectively. There were also reductions in number of fronds when treated with LPM, GPM, GOP, GOO, and GOPD. There were no reductions in frond numbers on tassel fern with any herbicides tested. However, there were reductions in frond length from 6 of the 10 herbicides evaluated. The most sensitive fern to herbicides evaluated in 2004 was leatherleaf with reductions in frond length and number of fronds with 6 of the 10 herbicides tested. While all herbicides tested on southern shield fern appeared to be safe, especially in the 2004 study, tassel fern and holly fern appear to be more sensitive. GPD proved to be a safe herbicide for all species tested in both 2004 and 2005. In 2005 all plants from all treatments were considered marketable by the end of the study. However there was significant visual injury observed on the holly fern treated with LIB at 60 and 90 days after treatment which might reduce their early marketability.

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Richard G. Greenland and Kirk A. Howatt

Nightshade species are difficult to control in tomato production and their interference reduces both tomato yield and quality. Rimsulfuron can be used to control nightshades, but species and biotypes vary in their response to rimsulfuron. The objectives of this study were to evaluate control of hairy nightshade (Solanum sarrachoides Sendt.) and eastern black nightshade (Solanum ptycanthum Dun.) by rimsulfuron and compare North Dakota eastern black nightshade accession response to three acetolactate synthase (ALS)-inhibitor herbicides. In field studies conducted at Oakes, N. Dak., rimsulfuron at rates of 26 or 53 g·ha–1 a.i. was applied within 1 week after transplanting tomato (EPOST) or 2 to 4 weeks after transplanting (POST). Rimsulfuron gave excellent control of hairy nightshade when applied POST, and poor to excellent control when applied EPOST, with control being much better when hairy nightshade had emerged before the EPOST application. Rimsulfuron at 53 g·ha–1 provided greater control than at 26 g·ha–1 only for the EPOST applications. Rimsulfuron controlled hairy nightshade which allowed eastern black nightshade (which was not controlled by rimsulfuron) to dominate tomato. Tomato yield was lower when dominated by hairy nightshade than by eastern black nightshade. This was due to the earlier emergence and faster growth of hairy nightshade compared to eastern black nightshade. Tomato yield was higher in the hand-weeded check than for all other treatments in 1999, the only year the hand-weeded check was included in the study. Greenhouse studies on plants grown from seed collected at the experimental site verified that eastern black nightshade was tolerant to rimsulfuron but was controlled by tribenuron and imazethapyr. Rimsulfuron can be used in tomato production to control hairy nightshade, but not the accession of eastern black nightshade found in this study. Chemical names used: N-((4,6-dimethoxypyrimidin-2-yl)aminocarbonyl)-3-(ethylsulfonyl)-2-pyridinesulfonamide (rimsulfuron); (α,α,α-trifluoro-2,6-dinitro-N,N dipropyl-p-toluidine) (trifluralin); methyl 2-[[[[(4-methoxy-6-methyl–1,3,5-triazin-2-yl)methylamino]carbonyl]amino]sulfonyl]benzoate (tribenuron methyl); (±)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo–1H-imidazol-2-yl]-5-ethyl-3-pyridinecarboxylic acid (imazethapyr).

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Steven M. McCulloch and Jeffrey L. Britt

, Indianapolis); trifluralin (Treflan) μ,μ,μ-Trifluoro-2,6-dinitro- N,N -dipropyl-p-toluidine, (DowElanco, Indianapolis); isoxaben + treflan (Snapshot TG) iV-[3-(l-ethyl-l-methylpropyl)-5-isoxazolyl]-2,6-dimethoxybenzamide and μ,μ,μ-Trifluoro-2,6-dinitro- N

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Brian A. Kahn, Niels O. Maness, Donna R. Chrz and Lynda K. Carrier

Silk. Hybrid cultivars were Cherriette; Crunchy Royale; Fireball; and Red Satin. Plots received preplant-incorporated urea to supply 56 kg·ha −1 N; preplant-incorporated trifluralin at 560 g·ha −1 for weed control; and sprinkler irrigation. Two

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Brian A. Kahn and John P. Damicone

), thermic Typic Udifluvent]. No plastic mulches were used. Weeds were controlled with a broadcast preplant-incorporated application of trifluralin (Treflan; Helena Chemical Co., Collierville, TN) at 560 g·ha −1 supplemented by hoeing and machine cultivation

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Glendon D. Ascough, Johannes van Staden and John E. Erwin

trifluralin are synthetic herbicides used for weed control and disrupt microtubule assembly during cell division. They are often more effective than colchicine because they have a higher affinity for plant tubulins ( Dolezel et al., 1994 ). Effectiveness of