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Eric A. Kohler, Clark S. Throssell, and Zachary J. Reicher

Ground ivy is a common broadleaf weed that disrupts turf uniformity and is difficult to control. The objective of this field research was to evaluate cultural and chemical control of ground ivy. Increasing annual nitrogen fertilizer applications from 0 to 196 and 293 kg·ha-1 reduced ground ivy cover by 24% and 32%, respectively. At 26 weeks after treatment, 1.1 kg·ha-1 isoxaben applied in May limited ground ivy spread by 34% compared to the control. Triclopyr, 2,4-D, or fluroxypyr applied at the highest-labeled rate in October provided superior ground ivy control by the following May. Combining an annual fertility program of 196 kg·ha-1 nitrogen and an application of 1.1 kg·ha-1 isoxaben with or after an application of 2,4-D, fluroxypyr, or triclopyr in the fall can maximize ground ivy control. Chemical names used: N-[3-(1-ethyl-1-methylpropyl)-5-isoxazolyl]-2,6-dimethoxybenzamide (isoxaben); [(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid (triclopyr); (2,4-dichlorophenoxy)acetic acid (2,4-D); [(4-amino-3,5-dichloro-6-fluoro-pyridyl)oxy]acetic acid (fluroxypyr).

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R.W. McMahon, R.K. Lindquist, M.L. Casey, A.C. Witt, and S.H. Kinnamon

A demonstration study was conducted to compare the effectiveness of biological and chemical control treatments on the greenhouse whitefly (GHWF) (Trialeurodes vaporariorum, Westwood) using poinsettia (Euphorbia pulcherrima Wild.) stock plants. Two identical greenhouse compartments, each containing 84 stock plants, were used. In the biological control compartment, three biweekly releases of Encarsia formosa (EF) were made, while in the chemical control compartment eight weekly applications of resmethrin or acephate aerosol treatments were made. Results showed that overall greenhouse whitefly populations in the chemical control compartment were slightly lower than in the biological control compartment. Cuttings taken from stock plants in the biological control compartment at the end of the experiment were commercially acceptable with regard to the presence of GHWF adults. Chemical names used: O,S-dimethyl acetylphosphoramidothioate (acephate), [5-(phenylmethyl)-3-furanyl] methyl 2,2-dimethyl-3-(2-methyl-1-propenyl)cyclopropane-carboxylate (resmethrin).

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Arturo López-Carvajal, R. Leonel Grijalva-Contreras, Cristóbal Navarro-Ainza, and Gerardo Martínez-Díaz

Approximately 50% of the asparagus plantations (3000 ha) in the Caborca, Sonora, area is furrow-irrigated. Under these conditions it is common to observe growing weeds in the furrow section, which impede water flow and compete for resources with the asparagus plant, finally reducing spear production and quality. Hence, the objective of this study was to validate herbicides to achieve an efficient annual weed control in the asparagus plantations. The validation plot was established in May 1998 on a commercial asparagus plantation that was highly infested mostly with annual grasses (Echinochloa colonum and E. crusgalli), and Amaranthus spp. and Portulaca oleracea as a secondary weeds. The herbicides and rates tested were: Prometrine (2 L·ha-1), Norflurazon (4 kg), Metribuzin (0.5 kg), Linuron (2 kg), and the control plot (no herbicide application). All the tested products showed significant weed control percentages compared with the control plot. Norflurazon, however, was clearly superior to the other herbicides, exhibiting a 100% control for a period of almost 18 weeks. Metribuzin had a 85% control for 12 weeks. Linuron and Prometrine exhibited a 68% and 47% control, respectively, for up to 12 weeks. Plant toxicity symptoms on the asparagus plant were not observed with any of the tested herbicides.

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Tadeusz Jacyna and James N. Cummins

Spininess is characteristic of many Malus species, especially American crabapple and Malus baccata L. Spininess often is present on rooted stoolshoots of commercial apple rootstocks (M.9, M.26, MM.111, and MM.106) and some rootstocks from the Geneva Breeding Program. This undesirable characteristic makes liner production costly and laborious. It is estimated that the cost of manual removal of spines amounts to ≈20% to 25% of total production costs. To counteract spininess, the stoolshoots of excessive spiny rootstock selections [74R5M9-760 (T/1), 74R5M9-707 (T/2), and 75R5M9BR-521 (T/3)] were chemically treated while growing at stoolbed. Chemical treatments consisted of single sprays of nontranslocated growth regulators Tamex (a.i. butralin) or Tamex AG (a.i. butralin + fatty alcohols C8- C10), and commercial auxin formulation (Tre-Hold A-112). Tamex AG and A-112 at applied rates brought about some phytotoxicity effects while Tamex did not. On average, Tamex application (1000, 2000, and 4000 ppm) reduced spine number to ≈80%, 68%, and 84% of T/1, T/2, and T/3 control plants, respectively. However, Tamex at 4000 ppm reduced the number of spines to 57% and 60% of control T/2 and T/3 plants, respectively, without any detrimental side effects. A parallel greenhouse experiment is being performed using commercial M.26 and Geneva 30 apple rootstocks.

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Tomomi Eguchi and Chieri Kubota

Daley, S. 2014 Chemical control of rootstock regrowth in grafted watermelon and its effects on plant growth and development. MS Thesis, Clemson Univ., Clemson, SC Daley, S.L. Hassell, R.L. 2014 Fatty alcohol application to control meristematic regrowth

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H.Y. Hanna, P.D. Colyer, T.L. Kirkpatrick, D.J. Romaine, and P.R. Vernon

Studies were conducted for 2 years in root-knot-nematode-infested soils to determine growth and yield response of `Dasher II' cucumbers (Cucumis sativus L.) to double-cropping with nematode-resistant tomatoes (Lycopersicon esculentum Mill.), using nematode-free cucumber transplants and preplant treatment with ethoprop nematicide. Cucumbers grown following the nematode-resistant `Celebrity' tomato during the same season produced significantly more plant dry weight, more fruit per plant, and higher premium and total yields than did cucumbers double-cropped with the nematode-susceptible `Heatwave' tomato in both years. The cucumber produced longer stems in 1992 and fewer culls in 1993 following resistant tomatoes. Cucumber plants raised in nematode-free soilless mix for 3 weeks before transplanting produced significantly longer stems and more plant dry weight than did direct-seeded cucumbers in 1992, but not in 1993; however, they produced significantly higher premium yield in both years, and higher total yield, more fruit per plant, and fewer culls in 1993. Preplant treatment with ethoprop significantly increased cucumber stem length, dry weight, premium and total yield, and number of fruit per plant in 1992 but not in 1993. Ethoprop treatment had no effect on the percentage of culls in either year. Chemical name used: O-ethyl S,S-dipropyl phosphorodithioate (ethoprop).

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Ruben Macias-Duarte, Raul Leonel Grijalva-Contreras*, Manuel de Jesus Valenzuela-Ruiz, and Fabian Robles-Contreras

The producers areas of onion in Mexico, are affected by the existence and increment of pathogens organisms of the soil like the fungus Pyrenochaeta terrestris, This problem increased its presence and damages due to the consecutive establishment of this vegetable year with year on the same soils. The fungus is activated and this disease developed when the soil temperature is increased. The disease infection of the plants causes rot and death of roots and small bulbs whit no commercial value, and low yields. According that the objective of the present research was to evaluate three treatments for the control of this organism pathogen: The experiment was carried out on INIFAP-CIRNO Experimental Station on a severally infested soil whit this fungus. The sow date was on 6 Jan. 2002, in this trial we used “local” variety. The treatments evaluated were Trichoderma (30 L·ha-1), Humega 8% (180 L·ha-1), Isofert 25 (400 L·ha-1) and a control (without treatment). The products were applied using the drip irrigation system. The results indicate that the treatments with Trichoderma and Humega 8% presented the lower percent of disease roots with 33% and those of more incidence were the control and Isofert 25 with 46% and 47% of disease roots, respectively. The results show 13% efficiency with the use of Trichoderma with respect to control; however this treatment did not affect the bulb weight and yield, control treatment obtained the greatest bulb weight and yield with 212 g for bulb and 80.9 t·ha-1 against 196 g and 71.9 t·ha-1, respectively, of the Trichoderma, which was seemingly a secondary negative effect in decrement the yield.

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David E. Yarborough and Timothy M. Hess

Three hundred, 1 m2 plots with either 0%, 25%, 50%, 75% or 100% dogbane or bracken fern weed cover were used in the study. The experimental design was completely randomized with two species, three treatments (mow, wipe and untreated), five densities and 10 replications. One half of each plot had weed cover and one half was kept weed free in order to compare the effect of weed density on yield. Plots were treated with either 10% v/v glyphosate in a hand held weed-wiper, mowed with a string trimmer or left untreated. Wiping was more effective than mowing for reducing weed numbers in the following year. However, wiping reduced yields compared to mowing at higher weed densities. Mowing proved more effective at increasing yields up to 50% weed cover compared to wiping or not treating. Averages from 1991 and 1992 study indicate mowing increases yields compared to wiping up to 50% then tend to decline, but yields remain greater than not treating.

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G.E. Brust and W.D. Scott

Nine treatments, arranged in a RCB design with 4 replications on 20m rows/plot, were all soiled applied and incorporated under black polyethylene mulch, prior to planting. The treatments were: methyl bromide (MB) 98 and 67 & chloropicrin at 168 kgha-1, metham sodium at 17 & 34 1ha-1, oxamyl at 1.6 & 3.21 1ha-1, fosthiazate 6.5 & 13 kgha-1, and a control. Four week-old `Crimson Sweet' watermelon (Citrullus lanatus) transplants were established 3 weeks after chemical applications were made. Soil samples were taken in the plastic row-middle, plastic edge, 30 cm off the plastic edge and 15, 30 & 45 cm deep at each sampling location 3 and 6 weeks after transplanting. The presence of Root-knot Nematode, RKN, (Meloidogyne spp.) was established by using `Mountain Pride' tomato as a bioassay. Fruit size and total yield were recorded and the economic return for each control practice calculated. The 1.6 1ha-1 oxamyl plots yielded 6,832 kgha-1 more than the control which corresponds to a return of $183 for the investment of that control. The 3.2 1ha-1 plots had a yield increase of 7,728 kgha-1 and a return of $103, followed by, in order of yield response, 17 1ha-1 Metham plots, 18,592 kgha-1 & $498, 34 1ha-1 Metham plots, 25,872 & $693, MB 67 plots, 35,952 kgha-1 & $752, and MB 98 plots, 37,072 kgha-1 & $851.

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J. Roger Harris, Alex X. Niemiera, Robert D. Wright, and Charles H. Parkerson

Three experiments were conducted to determine the feasibility of using Biobarrier, a landscape fabric with trifluralin herbicide-impregnated nodules, of various sizes to prevent root escape of trees from the drainage holes of 56-liter containers in below-ground pot-in-pot (P&P) and above-ground Keeper Upper (KU) nursery production systems. In addition, side holes or slits were cut in some container walls to test the effect of Biobarrier on the prevention of circling roots. In Expt. 1 (P&P), Betula nigra L. `Heritage' (river birch) trees with no Biobarrier had root ratings for roots escaped through drainage holes that indicated a 5-fold increase in numbers of roots than for treatments containing Biobarrier. All Biobarrier treatments reduced root escape and resulted in commercially acceptable control. In Expt. 2 (KU), control and the Biobarrier treatment river birch trees (30 nodules) had commercially unacceptable root escape. In Expt. 3 (P&P), control and 10-nodule treatment Prunus × yedoensis Matsum. (Yoshino cherry) trees had commercially unacceptable root escape, but treatments containing 20 and 40 nodules resulted in commercially acceptable control. Biobarrier did not limit shoot growth in any of the experiments. The results of these experiments indicate that Biobarrier did not prevent circling roots, but sheets containing at least 8 or 20 nodules of trifluralin acceptably prevented root escape from drainage holes in the pot-in-pot production of 56-liter container river birch trees and Yoshino cherry trees, respectively.