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Because of the limited number of herbicides in spinach, beet, and swiss chard, a screening study was initiated to identify new preemergence herbicides. Field soil at the study was a fine sandy loam. The study was initiated on 8 Apr. 2004 at Bixby, Okla. Each plot had four direct seeded rows of spinach, beet and chard. 22 treatments were replicated four times in a RBD that included a nontreated check. Treatments used 12 preemergence herbicides. Herbicides were applied PRE with a research sprayer at 20 GPA in a 6-ft swath perpendicular to crop rows. The experimental area received 0.5 inch of irrigation after application. Callisto (mesotrione) and V10146 (Valent exp. compound) both resulted in 100% death of beet, chard and spinach seedlings. Herbicides that had injury at or below Dual Magnum included Pyramin (pyrazon), Nortron (ethofumesate), Lorox (linuron), and Bolero (thiobencarb) tank-mixed with Bio-Power. Yields were zero for the nontreated check and several treatments due to weed competition and the lack of crop plants in some plots. Treatments with the highest beet yields included Dual Magnum at 0.5 lbs/acre, Pyramin at 3.6 lbs/acre, and Outlook (dimethenamid-P) at 0.25 lbs/acre (11,822, 8,034, 8,010 lbs/acre respectively). Highest chard yields were from Dual Magnum at 0.5 lbs/acre, Pyramin at 3.6 lbs/acre, Outlook at 0.5 lbs/acre + Bio-Power, and Outlook at 0.5 lbs (12,753, 12,596, 11,495, and 10,563 lbs/acre, respectively). Spinach yields were highest for Dual Magnum at 0.5 lbs/acre, Define (flufenacet) at 0.3 lbs/acre, and Outlook at 0.5 lbs/acre + Bio-Power (4,465, 4,259, and 3,207 lbs/acre, respectively).

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Little information is available on phytotoxic effects to annual bedding plant species from herbicides commonly used on container-grown woody plant species. Viol×wittrockiana `Crystal Bowl True Blue', `Imperial Antique Shades', and `Maxim Orange' were grown in 2.54-liter (#1) containers using an amended 6 pine bark: 1 sand medium. Five days after containerizing, each cultivar was either hand-weeded or treated with one of 13 granular or spray, pre- or post-emergence herbicides, within recommended rates in two separate studies. Herbicide phytotoxicity ratings were made 15, 30, 60, 90, and 120 d after treatment. Shoot dry weights were taken 120 d after treatment. Most injurious and persistently injurious herbicides were Rout 3G (oxyfluorfen + oryzalin), Pendulum 60 WDG (pendimethalin), and Ronstar 2G (oxadiazon). Low shoot dry weights closely correlated to injury rating. Least injurious herbicides included Pennant 7.8E (metolachlor), Surflan 4AS (oryzalin), Stakeout (dithiopyr), Pennant SG (metolachlor), and Derby SG (metolachlor + simazine). Southern Weedgrass Control, a granular formulation of pendimethalin, was among the least injurious, while Pendulum 60 WDG, a liquid formulation of pendimethalin, was most injurious. Evidence suggests that phytotoxic injury was greater on small, newly transplanted plants, though in some cases they were able to outgrow the injury.

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.g., Diebold et al., 2003 ; Morton and Harvey, 1992 ; Stall and Bewick, 1992 ; Williams and Pataky, 2008 ). Although this type of screening identifies hybrids that may be injured from postemergence herbicides, a more comprehensive understanding of the

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for screening stress tolerance in different plants, demanding lower resources, materials, and time than field trials ( Sakhanokho and Kelley, 2009 ). Hydroponics has been used to access herbicide tolerance or resistance in weeds ( Brosnan et al., 2014

Open Access

Abstract

Injury typical of the phenoxyacetic acid herbicides 2,4-D and 2,4,5-T was observed in a large area of St. Louis in the spring of 1969. Screening of chemicals from a local manufacturer of these herbicides revealed that at least 7 chemicals involved in the production of these herbicides produce symptoms similar to those observed in the field. Injury occurred from aqueous concn as low as 1 ppm as well as from vapors of the isobutyl ester of 2,4-D. The uniqueness of plant injury due to industrial emissions of herbicides demonstrates the need for using biological parameters in assessing air quality.

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Abstract

Considerable differences exist in the tolerances of onion inbreds to CIPC. Inbreds derived from ‘Iowa Yellow Globe’ were the most tolerant among the inbreds evaluated. Seedlings grown in the laboratory on agar containing the herbicide responded similarly to treated plants in field plots. The laboratory technique provides a fast, efficient method of screening large numbers of inbreds under controlled conditions.

Open Access

An above ground screening method to study cucumber root growth was developed using the herb icicle banding technique of Robertson et al. (Crop Sci 25:1084, 1985). Those roots that grow deeper or faster, sooner reach the herbicide, and sooner exhibit herbicide damage symptoms. Greenhouse pot trials showed that 1/4-1/2 lb/A atrazine could be used to produce distinctive symptoms, differentiate between depths of banding, and among different genotypes. Based on root washing experiments of a few cultivars, root length and/or mass correlated with herbicide symptom expression. One hundred diverse cucumber genotypes were tested in the greenhouse. Time to symptom expression was normally distributed among the genotypes; analysis of variance indicated significant genotypic differences. The herbicide banding technique was also useful for monitoring cucumber root growth in the field. Response time and severity varied with herbicide concentration, depth, and distance from the seed row. The diverse cucumber genotypes are now being tested in the field to further determine if there are significant genotypic differences and to compare greenhouse and field behavior.

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With the increase in popularity of natural medicine there is an ever growing market for the production of medicinal plants. In the last decade, screening trials of a number of species were conducted. The species currently under study are: angelica (Angelica archangelica; biennial, roots harvested), thyme (Thymus vulgaris; perennial, shoot harvested), German chamomilla (Matricaria recutita; annual, flowers harvested), horehound (Marrubium vulgare; perennial, shoot harvested) and dandelion (Taraxacum officinale; considered as a biennial, roots harvested). In 1990 the species were grown on three soil types (clay-loam, sandy loam and histosol) with different fertilization and irrigation practices. In 1991 two distinct trials were undertaken. The first considered herbicide efficiency and planting density. The second dealt with «organic» management strategies. Depending on the species, treatments of compost amendment, plastic mulch and implantation techniques were compared.

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Several methods using detached leaf tissues were investigated as potential early screening techniques for identifying strawberry germplasm resistant to Botrytis cinerea, which causes gray mold fruit rot. The fungus penetrates young leaves, remaining latent and symptomless under the cuticle until the leaves die, when the pathogen resumes growth and sporulates, providing almost all the primary inoculum for fruit infections. The best leaf screening method involved spraying potted strawberry plants in a 20±5 C greenhouse with a suspension of B. cinerea conidia, enclosing the plants in a plastic tent with a humidifier to provide humidity >95% for 72 hours, then resuming normal greenhouse conditions for several days before sampling young leaves. Leaf disks 1 cm in diameter were then cut, surface sterilized in 70% ethanol for 15 sec and 1% sodium hypoclorite for 2 min, dipped in paraquat herbicide (20 mg/l a.i.) to kill the tissues, rinsed twice in sterile water, and plated on water agar containing .01 % streptomyacin to inhibit bacterial growth. Plates were incubated at 21±2 C under 12 hour daylengths for seven days, and incidence and density of B. cinerea conidiophores on the disks determined. Despite much variation between disks within genotypes, clear differences in susceptibility between genotypes emerged which often correlated well with field suscpetibility to gray mold fruit rot.

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Abstract

The effect of bentazon on hosta (Hosta fortunei Tratt. cv. Hyacinthina), daylily (Hemerocallis L. cv. Sammy Russell), and yellow nutsedge (Cyperus esculentus L.) diffusive resistance and net photosynthesis was determined to screen for resistance to bentazon, a herbicide. Measurements of diffusive resistance and net photosynthesis were taken over 99 hours after treatment. Bentazon application increased diffusive resistance in yellow nutsedge 4 hours after treatment. In hosta and daylily, diffusive resistance increased by 24 hours; however, at 48 hours, treated plants responded the same as controls. Net photosynthesis was inhibited in yellow nutsedge within 4 hours after treatment, and the plants did not recover when measured after 4 days. Hosta net photosynthesis decreased after 24 and 48 hours, but net photosynthesis returned to the level of control plants after 4 days. Daylily net photosynthesis was not affected by bentazon application. No visual injury was detected from bentazon treatment in hosta or daylily, but nutsedge was severely injured. For rapid screening of herbicide tolerance, it may be possible to use photosynthetic measurements to determine susceptibility to bentazon. Chemical name used: 3-(1-methylethyl)-(1H)-2,1,3-benzothiazothiadiazin-4(3H)-one 2,2-dioxide (bentazon).

Open Access