We collected tubers from greenhouse-grown yellow nutsedge (Cyperus esculentus L.) control plants and plants foliarly-treated with 3.36 kg/ha of disodium methanearsonate (DSMA) or monosodium methanearsonate (MSMA). Where sufficient tubers were produced, they were separated into two classes, large and small. Some of the tubers were analyzed for elemental arsenic, and others were stored at 2 C and planted at various intervals. Vitality of tubers was noted in terms of sprouting and vegetative growth. Tubers collected from treated plants contained significantly more arsenic (4 to 33 ppm) than control tubers (1 ppm). Tubers collected from treated plants and planted without separation sprouted in significantly reduced numbers compared to control tubers. Small tubers contained a significantly higher concentration of arsenic (23 to 33 ppm) than large tubers (4 to 12 ppm). The treatments reduced the vitality of small tubers but had little or no effect on vitality of large tubers.

The maximum concentrations of 3-amino-s-triazole (amitrole) found in two flowing-water canals (1.13 and 0.65 cu m/sec) following treatment of a single ditchbank of each canal with 4.5 and 3.4 kg/ha of amitrole-ammonium thiocyanate (amitrole-T) were 31 and 43 ppb. Conjunctive treatment of both banks of another canal, prior to entry of water, resulted in a maximum of 98 ppb of amitrole upon turning 1.42 cu m/sec of water into the canal. Two hours after passage of the main body of amitrole-bearing water at the last sampling station on each canal, amitrole levels were down to approximately 1 ppb or less. The dissipation of amitrole in canals, for distances up to about 14.5 km, was a linear function of amitrole concentration and downstream flow. The rate of dissipation was fastest on a canal in which the herbicide was placed directly into the water (slope of 3.8), modest for a single bank treatment (slope of 2.7), and slowest where opposite banks of a canal were treated (slope of 1.8).

Bean (Phaseolus vulgaris L., var. Tendercrop) plants treated during germination with 100 ppm 5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone (pyrazon) were indistinguishable from untreated plants until 5 days after seedling emergence. Chlorosis began at the leaf margins, progressed inward, and became more severe until the leaves became necrotic and died. Similar symptoms were observed on leaves of plants treated with 25 and 50 ppm, but they appeared 4 to 10 days later. The light-microscope study of leaf tissue revealed that chloroplast form and arrangement were altered by pyrazon treatment. Chloroplasts in leaves of treated plants became round and swollen rather than discoid, contained no starch, aggregated in clumps, and developed an affinity for safranin stain.

Under Texas conditions, the potassium salt of 4-amino-3,5,6-trichloropicolinic acid (picloram) usually was more effective than the isooctyl ester formulation for control of live oak (Quercus virginiana Mill.), yaupon (Ilex vomitoria Ait.), winged elm (Ulmus alata Michx.), huisache (Acacia farnesiana (L.) Willd.), and honey mesquite (Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell). Possible reasons for the difference in effectiveness of picloram formulations were studied in the laboratory. Extensive degradation of the ester of picloram (96%) occurred in open Petri dishes after 72 hr exposure to ultraviolet (uv) light, compared to a loss of 26% for the salt of picloram. Forty-five percent of the isooctyl ester of picloram was lost at high temperatures (60 C), whereas only 2% of the potassium salt of picloram was lost after 1 week at 60 C from open Petri dishes in a dark oven. Application of the ester to soils reduced thermal and ultraviolet light degradation losses compared to losses from open Petri dishes. Loss of the ester was greater when applied in diesel oil to Petri dishes than in either water or paraffin oil. The salt of picloram leached most after 12.5 cm simulated rainfall in soil columns to the 17.5 to 30-cm level (907 μg), followed by the acid (360 μg), and last the isooctyl ester (0 μg). However, considerable acid (161 μg) was recovered at the 32.5 to 45-cm depth from the isooctyl ester treatment exposed to wet soils for 3 days, indicating hydrolysis of the ester to acid.

The phenology of reproduction was highly variable among 23 selections of medusahead (Taeniatherum asperum (Sim.) Nevski). Selections with markedly early and late maturity were observed. The phenology generally was consistent during 4 years of testing at Reno, Nevada, and during 2 years at Davis, California. Individual selections differed greatly in phenology between two locations. Some of the selections exhibited phenotypic plasticity in phenology when grown in competition with other weeds.

The fine structure of the chloroplasts of bean (Phaseolus vulgaris L., var. Tendercrop) was grossly altered by treatment with 5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone (pyrazon) when plants were grown in a treated medium. Alterations occurred first at the leaf margins and preceded visual symptoms. Chloroplasts became spherical and swollen rather than discoid, clumped rather than peripherally arranged, and were totally devoid of starch. Grana formation was inhibited; the thylakoids became swollen and perforated, and they ultimately disintegrated. Concomitant with grana inhibition was the increase in size and number of lipid globules. Occasional breakage of the outer chloroplast membrane was observed. It is proposed that these changes result because pyrazon inhibits thylakoid structural protein formation.

In a 3-year field study, from 51 to 1% of seed of velvetleaf (Abutilon theophrasti Medic) planted at 1 and 6-inch depths, respectively, produced established plants. Utilizing a microplot technique, 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) and the ammonium salt of 3-amino-2,5-dichlorobenzoic acid (amiben) were applied at 2 and 3 lb/A, respectively, at soil depths of 0, 2, and 4 inches. Velvetleaf seed were planted at depths of 1, 2, and 3 inches. Compared with the number of plants establishing in untreated plots, surface-applied amiben reduced the number of established plants 39, 23, and 29% from seed planted at depths of 1, 2, and 3 inches, respectively. Amiben at or below seed depth gave over 95% control, and when applied below the soil surface but above the seed, 86% control. Atrazine, surface-applied, reduced weed establishment 33, 62, and 85% from seed planted at depths of 1, 2, and 3 inches, respectively. When atrazine was at, below, or above the seed but below the soil surface, control was 96% or higher.

We constructed an injector-planter which simultaneously plants seed and injects herbicides. It effectively placed volatile herbicides under the soil surface in precise spatial relationship to crop seed. Rolling coulters, placed in front of the herbicide delivery system, enabled the unit to cut through trash better than previously-described equipment and, therefore, perform effectively under a wider range of soil conditions.

We surveyed soils that produce rice (Oryza Sativa L.) at the University of Arkansas Rice Branch Experiment Station at Stuttgart, Arkansas, to determine whether residues of 3, 3′,4,4′-tetrachloroazobenzene (hereinafter referred to as TCAB) accumulated with repeated applications of 3′,4′-dichloropropionanilide (propanil). We sampled Crowley silt loam with known histories of propanil application to determine the effect of depth, rate, and time on TCAB formation. Propanil and TCAB were measured by electron capture gas chromatography. Low concentrations of TCAB (<0.2 ppm) generally were detected in the surface 0 to 10.1-cm layer of soil receiving applications of propanil at rates of 6.7 kg/ha. Concentration and occurrence of TCAB decreased with increasing time and depth in soil.

In three field experiments at the University of Arkansas Rice Branch Experiment Station, Stuttgart, S-ethyl hexahydro-1H-azepine-1-carbothioate [molinate] at 2, 3, 4, and 6 lb/A was applied into the flood water 3, 6, 11, and 17 days after emergence of rice [Oryza sativa L.] and barnyardgrass [Echinochloa crusgalli (L.) Beauv.]. Molinate at 2 or 3 lb/A applied 3, 6, 11, or 17 days after emergence of rice and barnyardgrass, when weeds ranged from the one-leaf to tillering stages, provided acceptable weed control and rice tolerated these treatments satisfactorily. A rate of 3 lb/A frequently controlled barnyardgrass better than 2 lb/A, and usually was as effective as 4 or 6 lb/A. Sometimes, rates of 4 or 6 lb/A, applied 11 or 17 days after rice emergence, injured the crop moderately to severely and reduced grain yields.

The adsorption of 2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine (ametryne) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) varied greatly among 34 Puerto Rican soils was studied using the agitated slurry technique. Adsorption was expressed as a distribution coefficient (Kd), which is the ratio of the amount of herbicide adsorbed to the amount in the equilibrium solution. In general, diuron was adsorbed to a greater degree than ametryne. Adsorption of ametryne was positively correlated with organic matter and silt content but negatively correlated with pH of the soil. The inclusion of soil pH in a multiple regression analysis contributed the highest increase in explanation for adsorption of ametryne. Adsorption of diuron was highly correlated with organic matter content and cation exchange capacity. A correlation was found between adsorption of diuron and content of magnesium, and soil texture. Cation exchange capacity was the only inclusion soil property which, in addition to organic matter, significantly contributed to the adsorption of diuron. Temperature appeared to have a greater effect on the adsorption of diuron than on the adsorption of ametryne. Conversely, the effect of pH on the adsorption of ametryne was significantly greater than that of diuron.

The effect of 2,3,5-trichloro-4-pyridinol (pyriclor) on some photochemical reactions that bring about the formation of assimilatory power—the generation of adenosine-5′-triphosphate (ATP) and reduced nicotinamide-adenine dinucleotide phosphate (NADHP2)–at the expense of radiant energy has been determined using isolated spinach (Spinacia oleracea L., var. Viroflay) chloroplasts. The assimilation of carbon dioxide and cyclic photophosphorylation catalyzed by riboflavin-5′-phosphate (FMN) both showed inhibition at a rather high level of the pyridinol. However, oxygen evolution and non-cyclic photophosphorylation were strongly inhibited. Evidence is presented to support the conclusion that the locus of attack is the oxygen-evolving system and/or Pigment System 2 of the photosynthetic apparatus.

Two phototoxic compounds, xanthotoxin (8-methoxysporalen) and bergapten (5-methoxypsoralen), were isolated from spring parsley [Cymopterus watsonii (Coult. & Rose) Jones] by thin-layer chromatography, and identified by comparison of Rf values, infrared spectra, and melting points, with pure samples. The concentration of xanthotoxin was two to four times that of bergapten in plant samples collected during the 2-month growing season. Seeds contained xanthotoxin and bergapten in equal concentrations.

Several herbicides were evaluated for control of western false hellebore (Veratrum californicum Durand). The dimethylamine salt and propylene glycol butyl ether esters of (2,4-dichlorophenoxy)acetic acid (2,4-D), potassium salt of 2-[(4-chloro-o-tolyl)oxy]propionic acid (mecoprop), and the butoxy ethanol ester of 2-(2,4,5-trichlorophenoxy)propionic acid (silvex) controlled 95 to 99% of the plants when applied at 2 lb/A followed by 2 lb/A of the dimethylamine salt of 2,4-D the second year. Optimum control was achieved when plants were treated after the last leaf had expanded and before flower bud initiation.

An antagonistic interaction between S-ethyl dipropylthiocarbamate (EPTC) and (2,4-dichlorophenoxy)acetic acid (2,4-D) was observed on sorghum (Sorghum vulgare Pers.) and corn (Zea mays L.) after 21 days growth in soil incorporated treatments. Increasing the 2,4-D concentration increased the antagonism to EPTC. The antagonistic interaction was also observed on sorghum grown in solution culture. The antagonistic interaction occurred when the site of uptake was restricted to either the root or shoot zone of sorghum. Uptake studies with 14C-EPTC indicated that 2,4-D does not interfere with uptake or subsequent movement of 14C radioactivity within sorghum plants. Respiration of sorghum treated with the combination EPTC-2,4-D appeared to be normal. Respiration of EPTC-treated plants was inhibited.

In a stationary sprayer in a laboratory, wear was not detected in nozzles delivering α,α,α-trifluro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) in 4.3 to 6.9 gpa (assuming 4 mph at 30 psi) after 60 hr of use. In contrast, there was 1.7 to 2.0% increase in discharge volume during the first 5 to 10 hr from nozzles delivering 12.9 to 26.6 gpa. Wear was attributed to the greater amount of liquid discharged through the larger nozzles. Average wear in stainless steel nozzles was 1.7% as compared with 2.5 and 2.6% in brass and aluminum nozzles, respectively, delivering 4.3 to 26.0 gpa over a 60-hr period, while volume decreased 4.1% in nylon nozzles. Although trifluralin concentrations in the field were lower when the herbicide was applied in 2.7 or 5.4 gal of carrier/A, as compared to nozzles discharging 8.0 to 31.0 gpa, control of smooth pigweed (Amaranthus hybridus L.) was 95% or higher with all carrier rates 6 months following application.

In the greenhouse, five crops were grown in soil containing trichloroacetic acid (TCA) at 3 to 24 ppm. Based on seedling yields, corn (Zea mays L., var. Morden 88) and oats (Avena sativa L., var. Rodney) were relatively tolerant to TCA at all rates, barley (Hordeum vulgare L., var. Conquest) and rye (Secale cereale L., var. Antelope) were tolerant at lower rates, but wheat (Triticum aestivum L., var. Manitou) suffered injury at all rates. When TCA-2-14C was applied to the roots of wheat and oats seedlings in water or nutrient solution, wheat seedlings absorbed more TCA-2-14C than oats. Potassium cyanide (KCN) and 2,4-dichlorophenoxyacetic acid (2,4-D) decreased TCA-2-14C absorption by wheat more than that by oats. From 5 to 21 days after application, wheat retained two to four times as much TCA-2-14C as oats. Thus, half of the TCA-2-14C in shoots and roots of wheat disappeared in 11.3 and 11.4 days, respectively, compared with 7.9 and 3.5 days for oats. Based on this investigation, the difference in susceptibility of wheat and oats to TCA appeared to be governed by the metabolic processes involved in absorption and dissipation.

We developed two tractor-mounted spraying systems which utilize compressed air for dispensing the spray. The nursery sprayer consists of a spraying platform, two windshields, and two hand booms, and was developed to spray brush up to 6 ft tall. A field sprayer was developed to spray brush up to 15 ft tall. This sprayer has two 20-ft booms, mounted on a modified front end loader which could be rotated hydraulically to either side of the tractor.

We constructed a foam applicator capable of creating 300 to 400 gal of foam from 1 gal of water. The equipment was successful for applying herbicides in cotton (Gossypium hirsutum L., var. Stoneville 213) and soybeans (Glycine max Merr., var. Lee) after emergence. Weed control was equal with applications in foam as compared to conventional applications in water sprays. Foam production was highly dependent on the type and concentration of surfactant used. Various additives increased foam persistence in laboratory studies. However, for maximum effectiveness under field conditions, additives are needed that are more effective in increasing foam persistence than the ones evaluated.

Studies were conducted to determine the tolerance of several crops to herbicide sprays containing three spray drift control adjuvants, a cross-linked polyacrylate (Norbak), a pseudo-plastic spray gel agent composed primarily of natural carbohydrates (Dacagin), and hydroxyethylcellulose (Vistik). Other studies were conducted to observe the effect of the adjuvants on the efficacy of 1,1′-dimethyl-4,4′-bipyridinium ion (paraquat) when used with or without a surfactant, the effectiveness of the adjuvants in preventing 3-amino-s-triazole plus ammonium thiocyanate (amitrole-T) from being washed off plants, and the effect of the adjuvants in reducing vapor loss of the ethyl ester of (2,4-dichlorophenoxy) acetic acid (2,4-D) from leaves. Little increased injury was caused from the addition of the adjuvants to herbicides sprayed on several crops. The adjuvants added to paraquat were not effective substitutes for surfactant; however, Dacagin or Vistik added to paraquat combined with surfactant did not reduce the efficacy of paraquat. Norbak reduced the efficacy of paraquat, with or without the addition of surfactant. The adjuvants did not prevent amitrole-T from being washed off plants. Results of vapor studies suggested that Dacagin and Norbak reduced vapor loss of the ethyl ester of 2,4-D from plant surfaces.