Foliar treatments of 4-amino-3,5,6-trichloropicolinic acid (picloram) induced rapid procambium activity in western iron-weed (Vernonia baldwini Torr.) leaves. Increased meristematic activity was followed by destruction of the phloem parenchyma, sieve elements, and companion cells. Cell destruction in the vascular bundle was concomitant with that in the mesophyll.

Spring parsley [Cymopterus watsonii (Coult. & Rose) Jones] was examined for phototoxicity by chick (Gallus domesticus, Arbor Acre 50 x Vantress hybrid) bioassay, after treatment with 2,4,-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), 4-amino-3,5,6-trichloropicolinic acid (picloram), and an approximate 4 to 1 mixture of 2,4-D and picloram. Spring parsley leaves treated with picloram and picloram-2,4-D were much less phototoxic to chicks than controls 4 weeks after treatment. When treatment was followed by warm weather, leaves treated with 2,4-D and 2,4,5-T were not phototoxic 4 weeks after treatment at the highest single dose that could be administered.

Labeled 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2, 4, 5-T), 2-methoxy-3,6-dichlorobenzoic acid (dicamba), 4-amino-3, 5, 6-trichloropicolinic acid (picloram), 1,2-dihydropyridazine-3,6-dione (MH), assimilates, and phosphoric acid were absorbed and transported basipetally from the lamina into the petioles of detached bean leaves (Phaseolus vulgaris L.). Upward transport in the lamina was slight, except when the petioles were in water. In contrast, labeled 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) was not transported basipetally, but some acropetal transport did occur. Vein-loading and transport of labeled assimilates, 2,4-D, dicamba, MH, and phosphate were greatly reduced by a prior treatment with 7-oxabicyclo(2.2.1)heptane-2,3-dicarboxylic acid (endothall). Detached leaves hold promise for use in absorption and transport studies.

n-Pentane was used to extract 3-(m-trifluoromethylphenyl)-1,1-dimethylurea (fluometuron) from soil-water samples. The microgram quantity of fluometuron in the n-pentane was measured at a wavelength of 242 mμ with an ultraviolet spectrophotometer and this measurement related to the fluometuron concentration in the soil-water sample. No measurable interference was noted in the n-pentane after the extraction of fluometuron from the soil-water samples. The procedure was developed for extracting and quantitatively determining fluometuron in soil-water samples.

Under field conditions in North Carolina, yearly retreatment was required to provide reasonable soil sterility when an initial rate of 40 lb/A was used for each of the compounds 3-(p-chlorophenyl)-1,1-dimethylurea (monuron), 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), and 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine). Lateral movement of these three herbicides was a major factor limiting their utility as soil sterilizers. Attempts to reduce lateral movement by using reduced herbicidal rates in combination with contact active additives were partially successful. The total soil sterilization performance index derived from sterility ratings and lateral movement ratings indicated that the combination of 5 lb/A of diuron and 2 lb/A of 1,1′-dimethyl-4,4′-bipyridinium salt (paraquat) could not be excelled by diuron or 5-bromo-3-isopropyl-6-methyluracil (isocil) regardless of the rate used. When used alone, the soil sterilization properties of diuron were equivalent to those for isocil, provided that the diuron rates were two and one-half times as great as those for isocil.

Requirements for germination and rate of juvenile root and shoot elongation of 23 medusahead (Taeniatherum asperum (Sim.) Nevski) selections were investigated in relation to osmotic stress. These were compared with the germination and elongation characteristics of other grasses. Aqueous solutions of different osmotic pressures were obtained by dissolving polyethylene glycol in water. Successive 4-bar increases in osmotic pressure markedly reduced medusahead germination until germination terminated at 16 bars. Other grass species exhibited higher germination than medusahead under osmotic stress. Medusahead juvenile root and shoot elongation under low and moderate osmotic pressure exceeded all other species tested.

The problem in determining the economic feasibility of mechanical, chemical, and combination weed control methods in corn (Zea mays L.) is a complex decision involving many factors. The effects of cost, yield, timeliness, and alternative uses of labor are the factors considered in comparing various methods of weed control in this study. Costs of weed control operations range from $2.84/A for two cultivations to $10.45/A for the most intensive, mechanical-chemical operation studied. Most common weed control methods have costs of approximately $3 to $4/A. Yields range from 83 bu/A for two cultivations to 96 bu/A with the highest cost chemical-mechanical weed control methods. All yields used in this study are supported by agronomic studies and are indexed on the basis of 100 bu/A for weed-free conditions. The consideration of both yields and costs does affect the selection of a weed control method. Considering only these two factors, mechanical methods have a slight advantage over chemical weed control methods. Penalizing mechanical methods because of delay or timeliness characteristics gives chemical methods an advantage by as much as $3.00/A. Alternative uses of labor, even though a common argument in selecting chemical or mechanical methods, is a very small item and has only moderate effects on the changes in net income.

A fast and efficient method of evaluating soil incorporators consists of incorporating a fluorescent dye into the soil, taking soil samples, removing the dye by a solvent, and determining the dye concentration. Pontacyl Brilliant Pink B was the best dye for incorporation studies and a fluorometer was the analytical instrument.

Distribution and degradation of 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) at 5, 10, 15, and 20 ppmw in red pine (Pinus resinosa Ait.) seedlings were investigated using 14C-ring-labeled simazine dispersed in agar medium. Simazine readily entered red pine roots and moved rapidly into stem and needles. Accumulation was greatest in roots, next in stems, and least in needles. Significant differences in simazine uptake by roots were observed among concentrations between 5 and 20 ppmw in the incubation medium. Radiochromatographic scans revealed that a small amount of simazine was degraded to three unknown compounds by both fresh and boiled homogenates from whole plants, needles, stems, and roots. There were no observable differences in the amount of simazine degraded by homogenates of each separate plant part.

Electronmicrographs of barnyardgrass (Echinochloa crusgalli (L.) Beauv.) grown under controlled conditions and treated with 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) at the one to three-leaf stages show that degradation of the chloroplast starts as a swelling of the fret system followed by swelling and disruption of the granal discs. In advanced stages of breakdown, the membranes of the grana and chloroplast envelope were ruptured. These changes were initiated 2 hr after treatment with rates of 2, 5, 10, and 20 ppm atrazine. The incidence of starch grains greatly decreased as the duration of treatment exceeded 4 hr. The mitochondria appeared normal throughout, not being affected by concentration or duration of treatment. The stage of growth at which plants were treated was insignificant in determining changes at the ultrastructural level. The ultrastructural changes preceded any macroscopically discernable symptoms of tissue breakdown.

Dormancy, longevity, and germination of seed of tall larkspur (Delphinium barbeyi Huth), duncecap larkspur (Delphinium occidentale S. Wats.), low larkspur (Delphinium nelsonii Greene), and western false hellebore (Veratrum californicum Durand) were investigated. Field studies were conducted in the Cache National Forest in Idaho at 8,000 ft elevation. With the exception of 12 of 400 buried duncecap larkspur seed, seed of all species in the longevity study germinated or disintegrated the first year under field conditions. No sound or viable seed was found at the end of the second year. Dormancy of most seed was broken in 13 to 19 weeks when seed were held at 33 to 34 F in moist sand in the laboratory or when seed were in contact with moist unfrozen soil under snow. Under optimum field conditions, the majority of the seed germinated by late March. Seedlings were well-established before snow-melt in June.

The differential phytotoxicity of an unidentified amiben conjugate (hereinafter referred to as amiben-X), obtained from giant foxtail (Setaria faberii Herrm.) treated with 3-amino-2,5-dichlorobenzoic acid (amiben) was tested in several plant species. Concentrations of amiben-X up to 10 ppm had no effect on radicle elongation in seedlings of soybean (Glycine max (L.) Merr.) or ivyleaf morningglory (Ipomoea hederacea (L.) Jacq.). Giant foxtail radicles were inhibited about 35% at 10 ppm. Amiben, amiben-X, and N-(3-carboxy-2,5-dichlorophenyl)-glucosylamine (hereinafter referred to as N-glucosyl amiben) were detected in seedling tissues of the three above species treated for 24 hr with 20 ppm amiben-X. The growth response of the plants to amiben-X probably resulted from the action of the amiben released by plant hydrolytic activity on amiben-X; amiben-X itself is considered to be relatively nonphytotoxic.

A shielded, tractor-mounted sprayer for research plots is described. Advantages of this sprayer for research plots are reduced spray drift, rapid and thorough cleaning between herbicide treatments, adequate mixing of herbicide suspensions, rapid and accurate herbicide application, and facilitating plots large enough to take yield data with a combine.

Root applications of 9.0 μM 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) to soybean plants (Glycine max (L.) Merr., var. Chippewa) for 4 hr significantly reduced their transpiration rates. Similar reductions in transpiration rate were elicited by foliar applications of 900 μM. All atrazine treatments that reduced transpiration prevented dry weight accumulation by the plants and increased plant hydration. Root additions of glucose to de-rooted plants treated with atrazine had no influence on the transpiration reduction due to atrazine treatment but caused an increase in dry weight accumulation. There was a rapid accumulation of 14C-atrazine in the roots of the soybean plants from the culture solution with subsequent movement to the leaves. Leakage of 14C-atrazine out of the roots into the water medium after treatment termination was observed.

Herbicides were mixed with Drummer silty clay loam soil in 1-inch layers in the shoot, root, shoot and root, or seed zones for giant foxtail (Setaria faberii Herrm.). After 2 weeks in the greenhouse, foxtail tops were harvested and dry weights used as the measure of herbicidal effectiveness. All of the 11 herbicides evaluated caused a reduction in dry weight when placed in the shoot zone. When placed in the root zone, only 3-amino-2,5-dichlorobenzoic acid (amiben) caused a reduction in dry weight. Most herbicides were just as effective, or more so, in the shoot zone as in the seed zone. Only amiben and N-1-naphthylphthalamic acid (NPA) were more effective in the seed zone than in the shoot zone.

Germination, growth, and potential phytotoxicity of sicklepod (Cassia obtusifolia L.) were studied. Seed germination occurred in the temperature range from 18 to 36 C, but rapid seedling growth occurred only between 30 and 36 C. Seed dormancy caused by a waxy coat resulted in only 15% germination in soil over a 12-month period. A 1:15 (g/ml) water extract of sicklepod tops inhibited germination of cotton (Gossypium hirsutum L.) and oat (Avena sativa L.) seed. Incorporation of sicklepod residues in soil reduced germination of cotton seed but increased persistence of sericea (Lespedeza cuneata (Dumont) G. Don.) and crimson clover (Trifolium incarnatum L.) because damping-off was almost eliminated. There was evidence in nutrient cultures that sicklepod released a phytotoxic residue from its roots, reducing growth of cotton but having no effect on soybeans (Glycine max (L.) Merr.). Sicklepod grew well in soils ranging from pH 3.2 to 7.9. Sicklepod response to N, P, and K levels was similar to cotton and higher than that of soybeans.

Chromatographic procedures were developed for use in the laboratory studies of the breakdown of N-(p-bromophenyl)-N′-methoxy-N-methoxyurea (metobromuron) in soils. Both thin-layer and gas chromatographic procedures were developed to determine the known and/or suspected metabolic products occurring from the microbiological transformations in soil. Extraction of 3 soils, after 5 days of equilibration, yielded all the metabolites. Neither the gas chromatographic or thin-layer procedures were affected by soil extractives.

The Weed Science Society of America operates a placement office as a service to its members. Listings of “Positions Desired” and “Positions Available” received each 3 months by Orvin C. Burnside, Chairman, Manpower Placement Service of WSSA, Department of Agronomy, University of Nebraska, Lincoln, Nebraska 68503 are published in Weed Science. Once a listing is published it is then discarded. If one wants a listing rerun it will have to be resubmitted. One man from each state and province is asked to provide “Positions Available” and “Positions Desired” for his area once every 3 months. Individuals or companies also may send the necessary information directly to O. C. Burnside.

Dr. F. L. Timmons, of the USDA Agricultural Research Service, was in Somalia, Africa, March 21 to April 17, 1968 on an assignment with the Wyoming University USAID Program in that country. While in Somalia, he surveyed weed problems in irrigation canals and irrigated cropland, initiated several control experiments with herbicides, and conferred with Wyoming and Somali scientists and specialists on a program for weed control.