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Annamarie Pennuci

Novel and standard herbicides were applied alone, sequentially, or tank-mixed to determine weed control efficacies and tolerances in 15 species of field-grown herbaceous perennials. Autumn applications provided excellent but short-term broadleaf (BL) and annual grass (AG) weed control. Early spring applications were equally effective and of longer duration. Mid- and late spring treatments provided moderate to poor control of AG and poor control of winter perennial BL. Single applications of prodiamine provided season-long control of AG and of spring germinating BL. Greatest number of weed species were controlled by DCPA. Increased duration occurred with tank-mixes of DCPA + pendlimethalin, DCPA + quinclorac. Quinclorac provided excellent pre/post control of AG and some BL. Crop injury was minimized with directed applications. Isoxaben provided excellent preemergent control of BL. Tank-mixes improved AG control. Treatments applied prior to, or at the same time as mulch applications increased weed control and lessened drought stress. Treatments applied over mulch were less effective, suppressed fewer weed species, were of shortened duration, and increased the likelihood of crop injury.

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B. Jack Johnson

Low rates of preemergence herbicides were applied with postemergence herbicides as sequential applications or as tank-mixed applications for large crabgrass [Digitaria sanguinalis (L.) Scop.] and goosegrass [Eleusine indica (L.) Gaertn.] control in Kentucky bluegrass (Poa pratensis L.). In 1991, a higher percentage of large crabgrass control (83%) was obtained in late August from sequential applications of oxadiazon at 2.2 kg·ha-1 applied in early March and followed by fenoxaprop at 0.20 kg·ha-1 in June than when oxadiazon (62%) or fenoxaprop (11%) was applied alone. During this period, sequential applications of oxadiazon at 2.2 kg·ha-1 and monosodium salt of MAA (MSMA) at 2.2 kg·ha-1 achieved 79% control of large crabgrass, while the control was at ≤46% when MSMA or fenoxaprop was applied to plots previously treated with pendimethalin at 1.7 kg·ha-1 or dithiopyr at 0.28 kg·ha-1. There was no advantage from sequential applications of preemergence and postemergence herbicides for large crabgrass control in 1992, when compared with postemergence herbicides applied alone. Large crabgrass control in late August was higher over 2 years from tank-mixes of pendimethalin at 1.7 kg·ha-1 with fenoxaprop at 0.14 kg·ha-1 (80%) than when pendimethalin (28%) or fenoxaprop (55%) was applied alone at the same rates. The control was also higher from tank-mixes of pendimethalin at 1.7 kg·ha-1 with MSMA at 2.2 kg·ha-1 (92%), when compared with MSMA (77%) alone. The response was similar from tank-mixes of dithiopyr at 0.28 kg·ha-1 with fenoxaprop at 0.14 kg·ha-1 (98%) or with MSMA at 2.2 kg·ha-1 (98%), when compared with dithiopyr applied alone (81%) at the same rate. Quinclorac applied alone at 0.84 kg·ha-1 controlled large crabgrass as effectively as when applied to plots previously treated with preemergence herbicides or when applied tank-mixed with preemergence herbicides. None of the preemergence herbicides applied at low rates with postemergence herbicides (fenoxaprop, MSMA, or quinclorac) controlled goosegrass. Chemical names used: 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); 3-[2,4-dichloro-5-(1-methylethoxy)-phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one (oxadiazon); N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzen-amine (pendimethalin); and 3,7-dichloro-8-quinoline-carboxylic acid (quinclorac).

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Jennifer K. Boldt and James E. Barrett

A daminozide plus chlormequat chloride tank mix spray was applied to six Coleus cultivars or breeding lines at different times during propagation. For UF 03-8-10 and `Coco Loco', plants sprayed on day 7 or day 10 were shorter than control plants at transplant, but plants sprayed on day 13 were not. Other cultivars did not respond to single applications. Five of the six cultivars responded to application on days 7 and 13. Plants of UF 03-8-3 and `Coco Loco' were significantly shorter than control plants at transplant. Plants of UF 03-8-10, UF 03-6-1, and UF 03-17-8 were shorter than control plants at 3 weeks after transplant. `Hurricane Louise' did not respond to the tank mix. A second study found a cultivar specific response to three chemical treatments applied as a spray on day 10 of propagation. At transplant, UF 03-8-10, UF 03-8-3, UF 03-6-1, and `Coco Loco' plants sprayed with the tank mix at 2500 plus 1500 mg·L-1, respectively, were significantly shorter than the control plants. A uniconazole spray at 2 mg·L-1 reduced elongation in UF 03-8-10, UF 03-8-3, and UF 03-6-1, compared to control plants. Ethephon at 250 mg·L-1 reduced elongation in UF 03-8-10, UF 03-8-3, and `Coco Loco' plants. None of the chemical sprays reduced elongation in `Hurricane Louise' at the concentrations applied. Ethephon increased axillary branching in all cultivars, and induced lower leaf abscission in UF 03-17-8 and `Hurricane Louise'; leaf malformation in UF 03-6-1 and `Coco Loco'; and color alteration in UF 03-6-1, UF 03-8-3, and `Coco Loco'.

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Kelly P. Lewis, James E. Faust, James D. Sparkman IV and Larry W. Grimes

Poinsettia (Euphorbia pulcherrima Willd. Ex Klotzch) `Freedom Red' (FR), `Success Red' (SR), and `Winter Rose Dark Red' (WRDR) and pansy (Viola wittrockiana Gams.) `Colossus Yellow Blotch' (CYB), `Delta Pure Yellow' (DPY), and `Majestic Giants Purple' (MGP) were treated with 14 different tank mix combinations of daminozide and chlormequat ranging from 0 to 4500 mg·L-1 daminozide and 0 to 1500 mg·L-1 chlormequat. The tank mix treatments reduced stem elongation for all three poinsettia cultivars. Total bract area of FR and canopy bract diameter of WRDR decreased linearly as daminozide or chlormequat concentration increased, while bract area of SR was affected by daminozide alone. Anthesis was not delayed by any of the plant growth regulator (PGR) applications. For pansies, growth responses to the PGR treatments varied with cultivar. CYB growth was affected by daminozide alone, DPY growth was affected by daminozide and/or chlormequat, while MGP growth was relatively insensitive to both PGRs. Time to flower of pansy was not affected by the PGR applications. Chemical names used: 2-chloroethyl N,N,N-trimethylammonium chloride (chlormequat chloride); butanedioic acid mono (2,2-dimethylhydrazide) (daminozide).

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Don C. Elfving, Gregory A. Lang and Dwayne B. Visser

Prohexadione-Ca (P-Ca) and ethephon (ETH) were evaluated as potential inhibitors of growth and promoters of early flowering for high density orchard management of sweet cherry (Prunus avium L.) trees on vigorous rootstocks. Single applications (P-Ca at 125 to 250 mg·L-1 active ingredient (a.i.) or ETH at 175 to 200 mg·L-1 a.i.) to young, nonfruiting sweet cherry trees produced short-term, generally transient reductions in terminal shoot elongation, and did not stimulate flower bud formation. Tank-mix applications (P-Ca + ETH) usually produced a stronger, possibly synergistic, reduction in shoot growth rate. Single tank-mix applications either increased subsequent flower bud density on previous season shoots or had no effect; when a second application was made three weeks later to the same trees, subsequent flower bud density on previous season shoots and spurs on older wood increased ≈3-fold over untreated trees. Yield efficiency (g·cm2 trunk cross-sectional area) also increased nearly 3-fold. Chemical names used: (2-chloroethyl) phosphonic acid (ethephon); calcium 3-oxido-4-propionyl-5-oxo-3-cyclohexene carboxylate (prohexadione-Ca); polyoxyethylene polypropoxypropanol, dihydroxypropane, 2-butoxyethanol (Regulaid); aliphatic polycarboxylate, calcium (Tri-Fol).

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James R. Schupp, James R. McFerson and Terence L. Robinson

A tank mix of fish oil plus liquid lime sulfur has proven to be an effective chemical thinner for apples in the bloom and postbloom periods. This combination was labeled for use as a chemical thinner in Washington State in 2003. There are several concerns with fish oil when used in this thinning mixture. Phytotoxicity is one concern. Apple growers have a reluctance to utilize this oil because of its expense and repulsive odor. Research to date has been conducted using oil from a single small source in Washington State. Shipping fish oil across the country is expensive and the consistency and purity of fish oil from other sources is unknown. Fish oil may function as a surfactant and penetrant, and it may also have a direct thinning effect. The objective of these studies was to evaluate the efficacy of several surfactants and oils in combination with lime sulfur for thinning apples. Lime sulfur has been less effective as a thinner when used alone than when used with oil in our studies. Regulaid, LI-700, and Silwet L-77 were shown to be less effective than oils for achieving thinning. Vegetable oil has been very effective in the thinning combination, while petroleum oils have been effective in some eastern U.S. trials, but less effective in the west. Tank mixing fish oil with lime sulfur has remained among the best treatments in our trials, while vegetable oil also shows promise.

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J.D. Gaynor, A.S. Hamill and D.C. MacTavish

Metolachlor was evaluated for annual grass and eastern black nightshade (Solarium ptycanthum Dun.) control in processing tomato (Lycopersicon esculentum Mill.). Metolachlor applied preplant incorporated provided excellent (> 88%) control of annual grasses and eastern black nightshade. The metolachlor, metribuzin plus trifluralin tank mix applied preplant and incorporated into the soil provided better annual grass and eastern black nightshade control than the metolachlor plus metribuzin tank mix in two of three years. Nonincorporated and posttransplant treatments of metolachlor provided good annual grass control but failed to control eastern black nightshade. Tomato yield in all herbicide treatments was similar to that from hand weeded controls. Metolachlor dissipated from the soil throughout the growing season so that at the time of harvest <10% of that applied was recovered. Metolachlor residues in the fruit were hydrolyzed to deacylated (CGA 37913) or hydrolyzed conjugated (CGA 49751) metolachlor metabolizes. Analyses of extracts from treated fruits were found to be less than the detection limit of 50 ppb in the whole fruit harvested from selected metolachlor treatments. Chemical names used: 2-chloro-N -(2-ethyl-6-methylphenyl)-N -(2-methoxy-1-methylethyl) acetamide (metolachlor); 2,6-dinitro-N,N -dipropyl-4-(trifluromethyl)benzenamine (trifluralin); 4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-tlriazin-5(4H)-one (metribuzin); 2-(2-ethyl-6-methylphenyl)amino-1-propanol (CGA 37913); 4-(2-ethyl-6-methylphenyl)-2-hydroxy-5-methyl-3-morphol. inone (CGA 49751).

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Steven E. Newman, Michael J. Roll and Ronald J. Harkrader

Quaternary benzophenanthridine alkaloids (QBAs) isolated from plants in the family Papaveraceae are effective for the control of some fungal diseases. Extracts from Macleaya cordata, a species rich in QBAs, were formulated at 150 mg·L–1 QBA for spray application to greenhouse roses infected with Sphaerotheca pannosa var. rosae (powdery mildew). The QBA formulation was applied at 10-day intervals. For comparison, copper sulfate pentahydrate, piperalin, and fenarimol also were applied to mildew-infected plants within the same greenhouse at their respective labeled rates. One day after treatment, visible symptoms of mildew infection were reduced 60% by QBA, whereas fenarimol, copper sulfate pentahydrate, and piperalin reduced the symptoms of infection 50%, 75%, and 85%, respectively. Subsequent studies demonstrated that a tank mix of QBA and piperalin provided enhanced control of powdery mildew on rose. Results from this study indicate that QBAs have the potential to be developed as a biorational fungicide for greenhouse use with both fungicidal and fungistatic activity.

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Jeff S. Kuehny, Aaron Painter and Patricia C. Branch

Plug production has increased the finished quality and uniformity of bedding plants, making them one of the most important greenhouse crops grown. The wide range of cultural practices used by different growers to produce plugs, may influence the efficacy of plant growth regulators applied to the same crop in postplug production. Ten bedding plant species were grown from plugs obtained from two sources using different cultural practices. The plugs were transplanted to jumbo six packs and sprayed with either chlormequat/daminozide tank mix, ancymidol, or paclobutrazol at three concentrations at three times of year. The effect of each plant growth regulator varied by plant species and time of year applied. Source of plug material did have a significant effect on height and time of flowering of finished bedding plants and the use of plant growth regulators did not minimize the differences in height between sources in most cases.

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Steven E. Newman, Michael J. Roll and Ronald J. Harkrader

Quaternary benzophenanthridine alkaloids (QBAs) isolated from plants in the family Papaveraceae are effective for the control of some fungal diseases. Extracts from Macleaya cordata, a species rich in QBAs, were formulated at 150 mg·L–1 QBA for spray application to greenhouse roses (Rosa sp.) infected with Sphaerotheca pannosa var. rosae (powdery mildew). The QBA formulation was applied at 10-day intervals. For comparison, copper sulfate pentahydrate, piperalin, and fenarimol also were applied to mildewinfected plants within the same greenhouse at their respective labeled rates. One day after treatment, visible symptoms of mildew infection were reduced 60% by QBA, whereas fenarimol, copper sulfate pentahydrate, and piperalin reduced the symptoms of infection 50%, 75%, and 85%, respectively. Subsequent studies demonstrated that a tank mix of QBA and piperalin provided enhanced control of powdery mildew on rose. Results from this study indicate that QBAs have the potential to be developed as a biorational fungicide for greenhouse use with both fungicidal and fungistatic activity.