The degree and rate of volatilization, and the partial vapor pressures of the methyl, n butyl, and n octyl esters of 2,4-D [(2,4-dichlorophenoxy)acetic acid] were determined at ambient temperatures using a kinetic system approximating field-air conditions. The initial surface area/applied mass ratio (Q), as well as temperature and the type of compound, determined the volatility. Only when the Q values were kept constant did the volatility decrease with increasing chain length and decreasing saturated vapor pressure as expected. A mathematical model was constructed. Similar results were obtained for the amine salts which had saturated vapor pressures of ca 10−10 mm Hg at 38 C. Vapor drift can be essentially eliminated by use of the amine salts.

Three selections of johnsongrass (Sorghum halepense (L.) Pers.) were collected from three locations and designated as the N, NS, and S selections, respectively. The selections were studied for growth differences and for a differential response to dalapon (2,2-dichloropropionic acid). The N selection control plants flowered 2 weeks earlier than the other selections. The S selection yielded significantly greater root, rhizome, and total fresh weight than the NS and N selections. The N selection exhibited the most susceptibility to dalapon by producing the shortest plants, the least stem and leaf numbers, and the lowest shoot, root, rhizome, and total fresh weight of the three selections.

A mixture of microorganisms cultured under nonsterile conditions on propham (isopropyl carbanilate) herbicide as the sole carbon source was tested for its ability to degrade a number of chlorinated and nonchlorinated anilide compounds. In separate tests under pure-culture conditions, species of the microbial mixture reacted individually in a manner similar to the nonsterile whole. The microorganisms grew and respired rapidly on nonchlorinated anilides, but ring chlorination depressed respiration and inhibited growth. Studies on the dimethylphenylureas indicated that the two methyl groups were primarily responsible for the biological stability of these compounds. All other anilides were degraded by hydrolysis of the side chain followed by metabolic degradation of the ring. Appearance of aniline in the medium depended on the relative rates of production by side chain hydrolysis and disappearance by ring degradation. Acylanilides were hydrolyzed more rapidly than carbanilates and chlorinated rings were degraded much more slowly than unchlorinated rings. Chlorination affected rates of ring degradation and microbial respiration in the following order (most rapid to least rapid): 0 > 2,4 > 2,4,5 > 3 > 4 ≥ 3,4. It is proposed that this unexpected degradative sequence might be explained in terms of the degree of microbial toxicity in the system generated by the formation of chloroazobenzenes from chloroaniline intermediates.

Sequential application of cycloate (S-ethyl N-ethylthiocyclohexanecarbamate) at 3.4 kg/ha, phenmedipham (methyl m-hydroxycarbanilate m-methylcarbanilate) at 1.1 kg/ha, and trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) at 0.6 or 0.8 kg/ha, plus certain mechanical measures, controlled weeds during all periods of the growing season without significant injury to sugarbeets (Beta vulgaris L.). Early-season weed control was complete enough that the new selective mechanical thinners could have replaced labor for thinning. The additional labor required to bring the crop to harvest free of weeds was limited to one late-season hoeing, which required less than 10% of the total labor required in traditional weed control schedules without herbicides.

Differences in emergence, height, and leaf number between corn (Zea mays L.), soybean [Glycine max (L.) Merr.] and seven dicotyledonous weed species were measured until plants reached 15 cm in height or for 40 days, whichever occurred first, under several temperature regimes. Corn grew faster than the weeds at all temperatures. Initially soybean grew more rapidly than the weeds, but when they reached 15 cm in height the growth rate of weeds exceeded that of soybean. A positive and highly significant curvilinear relationship between plant height and leaf number was obtained for several temperature regimes for each species. Equations were derived for determining leaf number from plant height for each species.

Soybeans [Glycine max (L.) Merr.] planted conventionally or no-tillage tolerated approximately four times the recommended preemergence rates of linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] depending on the type planter used. Least injury to high rates of linuron was with a planter that placed seed slightly below the level of the surface of the field with a slightly rounded ridge of soil over the row. A planter leaving the seed under a slight furrow resulted in intermediate crop injury and a planter which deposited seed under a furrow 5 to 10 cm deep resulted in greatest crop injury. There was no consistent trend in the tolerance to linuron of soybeans planted conventionally or planted without tillage in small grain stubble with the straw removed. Row profile and its relation to seed placement was important in the tolerance of soybeans to linuron.

The percentage composition of fat, protein, nitrogen-free extract (NFE), fiber, and ash was determined for 50 weed and crop species. Data on 16 additional species were compiled from the literature. Generally, within a family there was a tendency toward a certain type of storage material. Seeds of the Polygonaceae and Gramineae were low in fat, high in NFE and, with few exceptions, low in protein. Seeds of the Leguminosae family were the highest in protein and, with the exception of peanut (Arachis hypogaea L.) and soybean [Glycine max (L.) Merr] were low in fat and high in NFE. Seeds of the Compositae, Cruciferae, Cucurbitaceae, and Solanaceae were high in fat, moderately high in protein, and low in NFE. The data may be valuable in the interpretation of the mode of action or basis for selectivity of herbicides.

The effects of seven preemergence herbicides on turfgrass quality, clipping yield, root growth, thatch accumulation, and carbohydrate reserves of three turfgrasses were measured. Nearly all herbicides caused some effect on one or more of the turfgrasses at some point during the 8-yr experiment, especially during mid-summer stress periods. The most consistently injurious herbicide was bandane (polychlorodicyclopentadiene) which caused a marked reduction in turfgrass quality, poor rooting, and increased susceptibility to stripe smut (Ustilago striiformis West. Niesel.). Clipping yields were reduced only in red fescue (Festuca rubra L. ‘Pennlawn’) by bensulide [O,O-diisopropyl phosphorodithioate S-ester with N-(20mercaptoethyl)-benzenesulfonamide], siduron [1-(2-methylcyclohexyl)-3-phenylurea], and terbutol (2,6-di-tert-butyl-p-tolyl methylcarbamate). Except for bandane, only siduron and terbutol caused significant reductions in root growth, and only in ‘Kenblue’-type Kentucky bluegrass (Poa pratensis L.). Thatch accumulation was reduced in ‘Merion’ Kentucky bluegrass treated with benefin (N-butyl-N-ethyl-α,α,α,-trifluoro-2,6-dinitro-p-toluidine) in ‘Kenblue’-type Kentucky bluegrass treated with bandane, benefin, bensulide, and terbutol; and in ‘Pennlawn’ red fescue treated with bandane, calcium arsenate, and terbutol. Carbohydrate reserves were not significantly different among treatments.

Dormancy of spurred anoda [Anoda cristata (L.) Schlecht] seeds was not broken 60 days after harvest by stratification, presoaking in tap water, or by treatment with thiourea, potassium nitrate, or kinetin. Dormancy was broken by scarification or treatment with concentrated sulfuric acid. A high percentage of seedling emergence was obtained when scarified seeds were planted in soil at depths of 7.5 cm or less. Emergence decreased as planting depth increased. No seedlings emerged at depths of 12.5 cm or greater. Even at depths of 15.0 cm germination occurred, but no seedlings emerged.

Three methods of applying linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] with trifluralin (α,α,α-triflu-oro-2,6-dinitro-N,N-dipropyl-p-toluidine) were compared for control of annual weeds in furrow-irrigated cotton (Gossypium hirsutum L. ‘Deltapine 16′). The linuron-trifluralin combinations controlled annual weeds effectively until harvest. There was no difference in cotton yield, boll components, or fiber properties among the three methods of applying combinations of linuron and trifluralin.

Removal of [2-14C] 2,4-D [(2,4-dichlorophenoxy)-acetic acid] from water was pronounced with Scenedesmus quadricauda (Turp.) Breb. and most effective uptake occurred at pH 4.7. Three other algae were relatively ineffective in removal of 2,4-D. Increasing Scenedesmus cell density increased 2,4-D removal, but the amount absorbed was not a linear function of cell density. Similarly, with a range of herbicide concentrations (0.01 to 1.0 ppmw) the amount removed was greatest at the highest concentration; however, a higher percentage of chemical was removed at lower concentrations. An equilibrium of 14C removal from water and 14C released to the water was reached by 4 hr. More herbicide was removed from water by Scenedesmus in darkness than in light and low temperature (2 C) reduced uptake slightly. Relatively high 2,4-D concentrations were required to reduce growth in any of the four algae and Scenedesmus was most sensitive. Scenedesmus metabolized [ring−14C] in 24 hr to several products which were found in suspension fluid and cells. Quantitatively, 3-OH-2,4-D [3-hydroxy-2,4-dichlorophenoxy)acetic acid] was the major metabolite, comprising 26% of the radioactivity extracted from cells compared to 15% from suspension fluid. A smaller amount of 5-OH-2,4-D [(5-hydroxy-2,4-dichlorophenoxy)acetic acid] was isolated from the suspension fluid and none from the cells.

The effect of soil pH on the disappearance of 14C ring-labeled atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], hydroxyatrazine [2-hydroxy-4-(ethylamino)-6-(isopropylamino)-s-triazine], and prometryne [2,4-bis(isopropylamino)-6-(methylthio)-s-triazine] were studied over a 5-month period in a Bladen silt loam soil under greenhouse conditions. Employment of an integrated system allowed simultaneous monitoring of degradation, volatilization, respiration, plant uptake, and leaching processes. A resulting balance-sheet indicated that a range of 87 to 99% of the 14C added could be accounted for after 5 months. Degradation was found to be the primary mode of dissipation. The pattern of atrazine degradation was characteristic of nonbiological processes, while prometryne degradation was probably by microbial action. Hydroxyatrazine was the major metabolite from the atrazine treatments while prometryne yielded an unknown and hydroxypropazine [2-hydroxy-4,6-bis(isopropylamino)-s-triazine]. Ex-tractable atrazine after 5 months amounted to 35% of the initial amount added in the pH 7.5 soil and 11% in the pH 5.5 soil, while prometryne occurred as 10% in the pH 7.5 soil and 42% in the pH 5.5 soil. Plant uptake and leaching occurred to a greater extent in the more alkaline soil with each chemical, but these pathways along with volatilization and respiration were minor contributors toward the disappearance of these herbicides.

Soil residues from annual trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N dipropyl-p-toluidine) applications were determined over a 4-year period on a Sharpsburg silty clay loam at Lincoln, Nebraska. A phytotoxic residue of trifluralin persisted in the soil for 1 or more years especially at above-normal rates of trifluralin. Repeated applications of trifluralin did not cause a significant buildup of trifluralin in the soil. There was little herbicide remaining in the soil during subsequent years from normal rates of trifluralin.

Two greenhouse experiments were conducted to study the influence of 12 soil-applied herbicides on the sprouting and mortality of yellow nutsedge (Cyperus esculentus L.) tubers. Alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide], butachlor [N-(butoxymethyl)-2-chloro-2′,6′-diethylacetanilide], cycloate (S-ethyl N-ethylthiocyclohexanecarbamate), EPTC (S-ethyl dipropylthiocarbamate), napropamide [2-(α-naphthoxy)-N,N-diethylpropionamide], and U-27267 (3,4,5-tribromo-N,N,α-trimethylpyrazole-1-acetamide) delayed sprouting of tubers and provided 6 to 12 weeks control, but failed to kill tubers. Tubers appeared to escape injury by failing to sprout until activity of the herbicides had substantially dissipated. Herbicides known to interfere with photosynthesis, atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], bromacil (5-bromo-3-sec-butyl-6-methyluracil), methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione], prometryne [2,4-bis(isopropylamino)-6-(methylthio)-s-triazine], San-6706 [4-chloro-5-(dimethylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone], and terbacil (3-tert-butyl-5-chloro-6-methyluracil) did not delay sprouting of tubers, but killed shoots after emergence. In addition to controlling vegetative growth, the photosynthetic inhibitors killed tubers by rapidly exhausting the food reserves of these storage organs.

Three blended foam adjuvants increased 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] uptake from aqueous solutions by detached live oak (Quercus virginiana Mill.) leaves as compared to uptake from water alone. There were no differences in honey mesquite [Prosopis juliflora (Swartz.) D.C. var. glandulosa (Torr.) Cockerell] control with 2,4,5-T or 1:1 combinations of 2,4,5-T with picloram (4-amino-3,5,6-trichloropicolinic acid) or with dicamba (3,6-dichloro-o-anisic acid) at 0.56 kg/ha whether applied in water + 0.5% (v/v) foam adjuvant or in a diesel oil: water (1:4, v/v) emulsion. Residual life of picloram in native forages was not extended by foam carrier as compared to water, water and surfactant, and diesel oil:water emulsion as carrier. Foam generation from adjuvants with expansion ratios (ER) of two to four was less susceptible to alteration from addition of commercially-formulated herbicides than was an adjuvant with an ER of seven. Foam adjuvant ER's increased in a curvilinear fashion as water temperature was increased from 5 to 50 C.

The application of individual droplets of an aqueous solution of As-74-labeled arsenic acid to the leaves, petioles, green stems and stalks of greenhouse-grown cotton plants (Gossypium hirsutum L. cv ‘Deltapine’) enabled the estimation of 100 ppm of As as the minimum effective internal concentration (MEIC) of arsenic from arsenic acid needed for the desiccation of cotton leaves. The spray application of arsenic acid to cotton plants (cv Lankart) in the field was calculated to have an overall efficiency of below 5 percent for this particular spraying operation. The application of aqueous arsenic acid to the abraded stalks of greenhouse-grown cotton plants (cv G-272) resulted in translocation of approximately 87% of the recovered arsenic so that treatment half-way around the stalk produced 70% desiccation. Treatment with sufficient quantities around the entire stalk resulted, in most cases, in complete desiccation and prevention of regrowth.

The distribution pattern of MCPA ([(4-chloro-o-tolyl)oxy] acetic acid) on leaf surfaces of three species was studied using the cathodoluminescence detection mode of a scanning electron microscope. On low-wax-content sugarbeet (Beta vulgaris L.) leaves MCPA concentrated in the depressions over the anticlinal cell walls when applied at high volumes (748 and 374 L/ha). At low volumes (23 L/ha), numerous small deposits of MCPA were randomly distributed over both anticlinal and periclinal walls. These distinct patterns were independent of herbicide concentration. Regardless of spray volumes, MCPA remaining on the waxy leaf surfaces of cabbage (Brassica oleracea L.) coalesced into small thick deposits. Large spray drops from high application volumes shattered on impact with the stellate hairs of turkey mullein (Eremocarpus setigerus Benth.) resulting in some MCPA reaching the leaf surface. Spray drops from low application volumes did not shatter but lodged on the hairs with very little reaching the leaf surface.

Eurasian watermilfoil (Myriophyllum spicatum L.) has invaded over 81,000 hectares in the Chesapeake Bay, 2,023 hectares in TVA reservoirs, and upwards of 32,000 hectares in Currituck Sound, North Carolina. Now it is causing concern in Florida because of its invasion of the Crystal-Homosassa River basin. In Yugoslavia and Pakistan, entomologists working on PL-480 grants found some 25 insect species feeding on eurasian watermilfoil. These species are potentially useful for the biological control of the weed in the United States.

The relative adsorption of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), triallate [S-(2,3,3-trichloroallyl)-diisopropylthiocarbamate], and diallate [S-(2,3-dichloroallyl)diisopropylthiocarbamate] was studied on several adsorptive surfaces. The herbicides were strongly adsorbed, with the following general trend: activated charcoal > peat moss > wheat straw (Triticum aestivum L.) ∼ cellulose triacetate > cation exchange resin > anion exchange resin > silica gel ∼ cellulose powder > kaolinite ∼ montmorillonite. Trifluralin and triallate were readily desorbed from montmorillonite by water, with miniminal desorption for peat moss, cellulose triacetate, and wheat straw.