Collections of plants of medusahead, Elymus caput-medusae L., were made from natural infestations in Nez Perce County and Washington County in northern and southern Idaho, respectively. The ash and silica content (dry weight basis) decreased as the plant matured. The total ash of the entire plant contained from 72–89 per cent silica. Similar percentages of silica in ash were obtained in the culms, heads, and seeds of the plant. X-ray diffraction patterns and polarizing microscope examinations showed the mineral form of silica to be opal. Heavy deposition of silica was found in the barbs of awns, in the epidermis of the leaves, culms, glumes and seeds, and in strands beneath the epidermis.

The persistence of soil-surface applied ethyl N,N-di-n-propylthiolcarbamate [EPTC] was studied at air velocities of ⅓ to 4 mph in special air-flow equipment. Persistence was inversely related to velocity though the effect was quantitatively changed by soil composition and the materials used in formulating the EPTC spray.

Livestock losses, mainly to cattle, from Astragalus miser Dougl. ex Hook. (timber milkvetch) have been reported since 1927. The species is found in the northwestern United States and also in Alberta and British Columbia. Recent taxonomic treatment distinguishes eight varieties. The most northern variety (A. miser var. serotinus (Gray) Barneby) and the most southern variety (A. miser var. oblongifolius (Rydb.) Cronq.) are the only two varieties known to cause livestock losses, but all varieties should be regarded as poisonous until it is known they are not. A. miser var. oblongifolius was controlled with 2 lb/A of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) or 2,4,5-trichlorophenoxypropionic acid (silvex). Removal of A. miser increased both cover and frequency of grass species.

Application of 20 to 40 lb/A dichlobenil made prior to emergence accomplished various degrees of control of pondweeds (Potamogeton diversifolius, P. foliosus, P. pectinatus, P. pusillus) and a slender naiad (Najas flexilis). Coontail (Ceratophyllum demersum) was affected only by the higher dosage. Limited control and growth inhibition was achieved on several forms of algae in early spring applications. However, applications made to rooted submersed aquatic plants and filamentous algae (Cladophora, Pithophora and Chara) at postemergence stage of development had little herbicidal effect.

Dichlobenil was not acutely toxic to fish at herbicidal concentrations. The range of median tolerance limits was 10 to 20 ppmw for pumpkinseed (Lepomis gibbosus), bluegill (L. macrochirus), redear sunfish (L. microlophus), and largemouth bass (Micropterus salmoides).

Complete control of established plants of absinth wormwood (Artemisia absinthium) was obtained with a single application of borax derivatives at 650 lb/A or less. Of several phenoxy-acetic, benzoic, and borax compounds which were tested, the most effective, economical treatment was 2,4-dichlorophenoxyacetic acid (2,4-D). Competition from perennial grasses was beneficial. Fall tillage prevented the establishment of absinth seedlings, and intensive tillage during the summerfallow year eradicated established plants.

Jimsonweed (Datura stromonium) was treated with carboxyl-labeled C14 2,4-dichlorophenoxyacetic acid (2,4-D*); auto-radiographs and extraction of radioactive materials were used to determine the movement and form of the herbicide. Activity rapidly decreased in the leafy tissue. There was an accumulation of activity in the stem, but very little accumulation in the roots. With the exception of the stem tissue where minor alteration of the herbicide occurred, 2,4-D* was the only radioactive material recovered from jimsonweed. A loss of radioactivity from the root systems indicated a possible detoxification mechanism for jimsonweed. Up to 25% of the 2,4-D* applied to jimsonweed was expelled from the roots in six weeks.

Strains of hoary cress, particularly within the lens-podded species (Cardaria chalepensis (L.) Hand.-Maz.), varied greatly in leaf size and shape, spreading ability, stand density, and reaction to treatment with several herbicides. Without competition, heart-podded hoary cress (C. draba (L.) Desv.) spread farther and produced a denser stand than either lens-podded or globe-podded cress (C. pubescens (K. A. Meyer) Jarm.), and, in general, was more susceptible to 2,4-dichlorophenoxyacetic acid (2,4-D) and trichlorobenzoic acid (2,3,6-TBA) than lens-podded cress. Within 12 strains of lens-podded hoary cress no relationship was found between susceptibility to 2,4-D or 2,3,6-TBA and any other characteristic.

The fate of the C14 label in ethyl N,N-di-n-propylthiolcarbamate (EPTC) was studied following root uptake by alfalfa plants for periods of 2 and 5 days. The uptake and movement of the C14 label in alfalfa was demonstrated by means of autoradiography and measurements of radioactivity with a Geiger-Müller detector. The amount of radioactivity accumulating in plants during the 5-day uptake period was approximately twice the amount accumulating in 2 days. The autoradiographs of plants receiving the 5-day uptake treatment showed an accumulation of C14 in the youngest tissue. Radioactive CO2 was liberated by the treated plants and their extracts contained a large number of C14 labeled compounds.

Naphthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), and 2-chloro-4-ethylamino-6-isopropylamino s-triazine (atrazine) were applied to Chlorella pyrenoidosa in an attempt to characterize mathematically the growth inhibition responses obtained. (Chlorella was found to serve well as a test organism.) Inhibition results induced by NAA and 2,4-D satisfactorily supported the hypothesis inherent in the kinetic interpretation. Results with atrazine were most satisfactorily interpreted by a probit analysis which showed large differences in rate of toxicity between high and low concentrations. This difference is thought to be responsible for the poor fit to a straight line in the reciprocal plots of the kinetic analysis. It is assumed that growth inhibition by atrazine resulted from a blocking of the photosynthetic process.

Preemergence herbicides for the control of crabgrass, (Digitaria ischaemum (Schreb.) Muhl. and D. sanguinalis (L.) Scop.) were applied on bluegrass sod at three different rates for three years to determine residual effects on the stand and vigor of perennial ryegrass, red fescue, tall fescue, and Merion and common Kentucky bluegrass seedlings. With few exceptions, the herbicides retarded stand and vigor of these turfgrasses seeded in turf killed with methyl bromide. Chlordane was least and a commercial arsenic complex plus 7% N most toxic to young seedlings. Seedlings of Merion Kentucky bluegrass were most resistant to herbicide injury. No appreciable decrease in original turf density was noted except for the arsenic complex material which severely injured bluegrass turf at the two heavier rates.

Germination of the same turfgrasses seeded in flats of sterilized soil in the greenhouse 1 day, 41 days, and 93 days after the application of preemergence crabgrass herbicides, showed the most reduction in emergence from treatments with DMPA [O-(2,4-dichlorophenyl) O-methyl isopropylphosphoramidoate], trifluralin (2,6-dinitro-N,N-di-n-propyl-alpha-alpha-alpha-trifluro-p-toluidine), DCPA (2,3,5,6-tetrachloroterephthalic acid), and dipropalin (N,N-di-n-propyl-2,6-dinitro-p-toluidine). Lead arsenate was least injurious to germinating seedlings. Tall and red fescue were more tolerant to herbicides than the other grasses studied.

Bristly thistle (Cirsium horridulum Michx.) is an important perennial weed in Alabama pastures. It may remain vegetative many years before flowering and may regrow from the roots after flowering. A heavily infested pasture produced about 10,000 seedlings per acre per year of which 73% established from January through April. There was an average of 150 achenes per head but many did not contain fully developed seed. Essentially equal numbers of red and yellow flowered types were found. From two to as many as six successive cuttings below the soil surface were necessary to kill thistle plants. Thistles were effectively controlled by 2,4-dichlorophenoxyacetic acid (2,4-D), and 2-methyl-4-chlorophenoxyacetic acid (MCPA).

The effects of thirteen plant growth regulators and herbicides on glucose absorption, metabolism, and incorporation in pea root tissues were studied. Both indoleacetic acid (IAA) and gibberellic acid (GA) caused no effects, while α-naphthalene-acetic acid (α-NAA) and β-naphthaleneacetic acid (β-NAA) caused an increase in catabolic and a decrease in anabolic processes, with the C-1 carbon undergoing the largest change. The absorption of glucose was also inhibited considerably by the synthetic auxins. The carbamates, isopropyl N-phenylcarbamate (IPC), n-Ethyl-N,N-di-n-propylthiolcarbamate (EPTC), and 3-(p-chlorophenyl)-1,1-dimethylurea (monuron) inhibited slightly the glucose absorption. All affected the catabolic process to a certain extent while only IPC caused a change in the anabolic process. Both 2,3,6-trichlorobenzoic acid (TBA) and 2,3,5-triiodobenzoic acid (TIBA) decreased glucose absorption and increased glucose-1-C14 catabolism. TIBA also affected the anabolic process. Other herbicides, 3-amino-1,2,4-triazole (amitrole), maleic hydrazide (MH), 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine), and 2,2-dichloropropionic acid (dalapon) caused varied degrees of inhibition to glucose absorption. Both simazine and dalapon increased C-1 catabolism and exerted no effect on the anabolic process. Only dalapon altered the catabolism of glucose-6-C14. Amitrole and MH decreased the over-all catabolic process with no effect on the pathway; both chemicals increased the anabolic process.

The use of insects in the biological control of weeds necessitates that these insects have very restricted host ranges. Specialized insects boring in stems or living in seed pods have adaptations which obligate them to their host plant. However, the leaf-feeding beetle, Chrysolina quadrigemina Suffrian, imported for the control of St. Johnswort (Klamath weed) (Hypericum perforatum L.) through its feeding habits, tropistic responses and synchronization of its life history to the growth phases of the plant has shown that it is restricted to its preferred host plant.

Swainsona salsula is an unpalatable legume of Asiatic origin which spreads by seed and lateral roots and has become a problem in some poorly drained, marshy, or saline areas of several western states. Its growth characteristics indicate a high potential for establishment along stream banks, irrigation canals, wasteways, pastures, and meadows with high water tables and other poorly drained areas. Its aggressiveness results in its dominance on such areas. 2-(2,4,5-trichlorophenoxy)propionic acid (silvex), 2,4-dichlorophenoxyacetic acid, (2,4-D), or 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) applied at 2 lb/A for 2 or more years in succession controlled swainsonpea satisfactorily on cropped land. 2,3,6-trichlorobenzoic acid (2,3,6-TBA) was also effective.

When applied in enough water to wet tubes of dry Pullman silty clay loam top soil to a depth of 22 inches, dimethylamine salts of 2,3,6-trichlorobenzoic acid (2,3,6-TBA) and polychlorobenzoic acid (PBA) were leached to about 20 inches; an amine salt of 2,4-dichlorophenoxyacetic acid (2,4-D) and the sodium salt of 2,3,6-trichlorophenylacetic acid (fenac) leached to 15 inches; esters of fenac, 3-phenyl-1,1-dimethylurea (fenuron), 3-(p-chlorophenyl)-1,1-dimethylurea (monuron) and amine salts of 2-(2,4,5-trichlorophenoxyl)propionic acid (silvex) and 2,4,5-trichlorophenoxy-acetic acid (2,4,5-T) leached to approximately 9 inches. Esters of silvex, 2,4,5-T, and 2,4-D remained in the top 3 inches of soil. The leaching with additional water was in the same general order as just given.

Seeds of winged elm (Ulmus alata Michx.) stored under moist conditions lost viability rapidly. Under dry conditions the seeds lived longer. Winged elm seeds would not germinate at 4 C or 42 C but did at temperatures between these points. Salt concentrations above 20,000 ppm killed the seed; concentrations below this inhibited germination; twelve per cent manitol solutions (16 atmospheres osmotic pressure) prevented germination; pressures lower than this decreasingly affected germination. If the soil moisture level was below 2%, winged elm seeds would not germinate. Removal of the outer husk of the seed did not affect germination. Winged elm seedlings did not emerge if planted at depths below ¼ inch.

Relative vaporization losses of five C14 ring-labeled 2-chloro-4,6-alkylamino-s-triazines were studied at 25 and 60 C. Herbicide solutions in 95% ethanol were deposited on metal planchets, dried and counted at intervals. The herbicides, ranked in order of decreasing volatility, were: trietazine (2-chloro-4-diethylamino-6-ethylamino-s-triazine), ipazine (2-chloro-4-diethylamino-6-isopropylamino-s-triazine), atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), propazine (2-chloro-4,6-bis(isopropylamino)-s-triazine) and simazine (2-chloro-4,6-bis(ethylamino)-s-triazine). Prometone (2-methoxy-4,6-bis (isopropylamino)-s-triazine) and the 2-hydroxy analogues of simazine and propazine, dissolved in water at pH 2–3 (HC1) before plating, showed no detectible loss in 25 hours at 60 C. Foliar penetration and acute toxicity following drop application of the five 2-chloro-triazines and prometone to corn, soybean, tomato, cotton, oat and sorghum appeared to be correlated with their water solubilities. A surfactant tended to enhance activity. Important differences were noted among species, although apparently not related to inherent herbicidal tolerance or susceptibility. Tomato was most sensitive to acute toxicity; soybean cotyledons were least permeable. Basipetal translocation was negligible under all conditions (e.g. 6 herbicides, 6 species, 2 solvents, with or without a surfactant). The 2-hydroxy analogues tended to translocate downward but appeared restricted by acute, acid (pH 2–3) destruction of the transport mechanism. Acropetal (apoplastic) movement of all compounds occurred readily with transpiration, reflecting the vasculature of the species. All 2-chlorotriazines and prometone (but not the two 2-hydroxy compounds) showed pronounced accumulation of C14 in the lysigenous glands of cotton. Root uptake and distribution of C14 within the plant body occurred generally for all compounds and species.

A single-gene homozygous recessive mutant in an S1 inbred line of corn resulted in an 8- to 10-fold reduction in 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one content. Aqueous suspensions of acetone extracts from low segregates formed little 2-hydroxy-4,6-bis(ethylamino)-s-triazine (hydroxysimazine) when incubated with 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine). Tolerance studies on 3:1 and 1:1 segregating ears indicated that the low segregates were somewhat less tolerant to 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) supplied in solution culture.

Paraquat (1,1′-dimethyl-4,4′-dipyridylium cation) removed weedy annual grasses from seedings of rose clover (Trifolium hirtum All.) and subclover (T. subterraneum L.) with only temporary damage to the clovers when applied at early growth stages. Paraquat applied under weed-free conditions reduced herbage yields of Lana woollypod vetch (Vicia dasycarpa Ten.) and Wimmera ryegrass (Lolium rigidum Gaud.) at three dates of application; neither herbage nor seed yield of rose or subclover was reduced.

Stationary and portable field sampling equipment and techniques are described for the collection of gaseous and aerosol forms of 2,4-D compounds. Air was sampled at the rate of 1 liter per minute through 10 ml of n-decane in a modified midget impinger maintained at approximately 1 C. Field sampling was conducted at two eastern Washington sites for approximately 106 days during the summer of 1963. The presence of isopropyl, butyl, and isooctyl esters of 2,4-D in the atmosphere was established by electron capture gas chromatography. Twenty-four hour average atmospheric concentrations of these esters ranged from undetectable to 3.1 μg/m3.