Vernolate (S-propyl dipropylthiocarbamate) injected into a sandy loam soil controlled a higher percentage of early weeds in soybeans (Glycine max (L.) Merr.) in 2 years out of 3 when compared with incorporated vernolate at the same rate by conventional methods. Late season weed control was enhanced by split applications of herbicides applied postemergence in sequence with vernolate. Chloroxuron (3-[p-(p-chlorophenoxy)phenyl]-1,1-dimethylurea) applied early postemergence plus 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron) or 2,4-bis-(isopropylamino)-6-(methylthio)-s-triazine (prometryne) applied in split applications as late and layby treatments gave the best weed control. Prometryne caused chlorotic veination in the upper leaves of the plants each year. In 1970, when prometryne was applied in sequence with incorporated vernolate, soybean plants were injured 30% compared with only 8% injury when the same herbicide was applied in sequence with injected vernolate at the same rate. The average seed yields were higher from injected vernolate at 1.12 kg/ha than from incorporated vernolate at 2.24 kg/ha. There was no difference in yield when vernolate was incorporated or injected at the same rate. Seed yields from the 3-year average were lower from plots treated with prometryne than from plots treated with linuron or 2-sec-butyl-4,6-dinitrophenol (dinoseb). Generally, the soybean seed quality was lower and seed size smaller when herbicide treatments failed to control weeds throughout the growing season.

Water from several bodies of surface water and sections from several plants were collected from eastern North Carolina and bioassayed for stimulation of witchweed (Striga lutea Lour.) seed germination. Stimulatory activity was detected in water from 22 of 29 different ponds, streams, and lakes and in sections from 118 (57 families) of 163 plant species. Witchweed germination stimulants evidently occur widely in nature.

Small field plots, 18 by 18 cm in size, were treated with S-(2,3,3-trichloroallyl)diisopropylthiolcarbamate (triallate) at rates equivalent to 2.8 kg/ha at five sites in Saskatchewan. After one growing season (5 months) the residues remaining in the 0 to 5 and 5 to 10-cm levels of soil were determined by gas chromatographic analysis. At all locations 16 to 27% of the applied herbicide was found in the top 5 cm while negligible residues were detected at the 5 to 10-cm level.

A time course study on the in vitro effect of 10–4 M (2,4-dichlorophenoxy)acetic acid (2,4-D) on the metabolism and incorporation of specific 14C-labeled glucose into pea (Pisum sativum L., var. Alaska) and corn (Zea mays L., var. Golden Cross) tissues showed a preferential release of C-1 as CO2 which was affected by 2,4-D. The glucuronic acid pathway was stimulated greatly in pea roots and slightly in corn stems; it was inhibited in corn roots. The pentose phosphate pathway was affected in an opposite pattern. The incorporation of both labeled carbon atoms into alcohol-insoluble residue was also affected by 2,4-D. The degree of effect, however, varied from pea to corn and from roots to stems. Analysis of the alcohol-soluble fraction revealed different effects of 2,4-D on labeling of some of the amino acids, an increase in fructose content, and an accumulation of malic acid.

Nineteen herbicides in various formulations were tested preemergence and postemergence for control of western bracken (Pteridium aquilinum (L.) Kuhn var. pubescens Underw.). Excellent suppression was obtained for 1 year with fall applications of granular formulations of 2,6-dichlorobenzonitrile (dichlobenil) at 6.7 and 10.1 kg/ha, 4-amino-3,5,6-trichloropicolinic acid (picloram) at 2.2 kg/ha, and 3,6-dichloro-o-anisic acid (dicamba) at 4.5 to 9.0 kg/ha. Bracken recovered rapidly after 1 year of suppression by dichlobenil, but other herbaceous species were killed. Bracken recovered considerably the second growing season after application of picloram or dicamba, although morphological effects were noticeable for 2 to 3 years, particularly from dicamba. No visual injury to grasses was apparent from picloram. Some injury to orchardgrass (Dactylis glomerata L.) was noted from dicamba.

Tolerance of Yuchi arrowleaf clover (Trifolium vesiculosum Savi) to preemergence application of dimethyl tetrachloroterephthalate (DCPA) and isopropyl m-chlorocarbanilate (chlorpropham) and preplant incorporation of N-butyl-N-ethyl-a,a,a-trifluoro-2,6-dinitro-p-toluidine (benefin), 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin), S-ethyl dipropylthiocarbamate (EPTC), and S-propyl dipropylthiocarbamate (vernolate) were evaluated over a 3-year period on two soils. DCPA did not injure Yuchi arrowleaf clover in any experiments over the 3-year period. Lower rates of benefin and chlorpropham caused either moderate or no injury depending upon the year and location. Yield reductions of Yuchi clover generally were greater on the Norfolk than on the Lucedale soil. Early injury, as reflected by the first forage harvest, was transitory in many instances.

The dipeptidase activity of the cotyledons of the squash (Cucurbita maxima Duch. ‘Hubbard’) increases during germination. Several herbicides inhibited this increase in various degrees. Those herbicides inhibiting the development of dipeptidase activity 70% or more were (2,4-dichlorophenoxy)-acetic acid (2,4-D), 3,6-dichloro-o-anisic acid (dicamba), (2,3,6-trichlorophenyl)acetic acid (fenac), and N-1-naphthylphthalmic acid (naptalam). Those inhibiting dipeptidase activity by 63 to 34% were 4-amino-3,5,6-trichloropicolinic acid (picloram), 2,6-dichlorobenzonitrile (dichlobenil), 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil), 3-amino-s-triazole (amitrole), 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), 7-oxabicyclo[2.2.1] heptane-2,3-dicarboxylic acid (endothall), and 5-bromo-3-sec-butyl-6-methyluracil (bromacil). Those causing only slight inhibition, 24 to 16%, were N,N-dimethyl-2,2-diphenylacetamide (diphenamid), isopropyl m-chlorocarbanilate (chlorpropham), and α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin); 3-(p-chlorophenyl)-1,1-dimethylurea (monuron) was essentially the same as the control. However, 2,2-dichloropropionic acid (dalapon), O,O-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl)-benzenesulfonamide (bensulide), N,N-diallyl-2-chloroacetamide (CDAA), and 2-chloroallyl diethyldithiocarbamate (CDEC) were somewhat stimulatory. When compared with previously reported herbicide activity on the proteinase activity, those herbicides which inhibited dipeptidase activity did not necessarily affect proteinase activity to the same degree.

Sunflowers (Helianthus annuus L.) produced maximum seed yields when kept weed free for a period of 4 to 6 weeks after planting. This was accomplished with one cultivation anytime between 2 and 6 weeks after the early planting in 1969, with two cultivations 2 and 4 weeks or 4 and 6 weeks after the late planting in 1969, and with one cultivation at 4 weeks after either the early or late planting in 1970. The average height of sunflower plants was not influenced by weed competition if weeded at either 2 or 4 weeks after planting, whereas, head and seed size were not affected if weeded at 4 weeks after planting. The oil content of seed was higher in plots with the least amount of weed competition.

Laboratory and greenhouse studies were conducted to determine the response of four plant species to 4-amino-3,5,6-trichloropicolinic acid (picloram). Germination of soybean (Glycine max (L.) Merr., var. Lee) seeds was inhibited, step-wise, by 10−8 to 10−3 M concentrations of picloram. Safflower (Carthamus tinctorius L.) germination was inhibited at 10−3 M; however, radish (Raphanus sativus L.) and barley (Hordeum vulgare L.) were not affected by any concentration studied (10−6 to 10−3 M). Measurement of several parameters of growth such as fresh and dry weight, shoot height, number and dimensions of leaves, percent necrosis, hypocotyl or epicotyl length, and hypocotyl diameter revealed that picloram was both growth promotive and inhibitory to safflower, radish, and barley. Levels of picloram required for growth promotion or inhibition varied with the species, stage of plant growth, herbicide concentration, the specific tissue, and the parameter being measured. Typical malformations such as twisting of stems, death of growing points, and occurrence of callus growth (depending on the species and herbicide dosage) were observed in picloram-treated seedlings. Studies on water loss by evapotranspiration suggested that picloram caused a possible alteration of stomatal behavior and/or a disturbance of water metabolism in plants under appropriate conditions.

A method is described to quantitatively record the upward force of an emerging seedling that exhibits epigeal germination. A soybean [Glycine max (L.) Merr.] seedling showed an average maximum emergence thrust of 434 g at 8 to 10 days after planting. Herbicides can be grouped into those that inhibit, have no effect, or stimulate the upward thrust exerted by an emerging soybean seedling. At the rates studied, the herbicide 4-amino-3,5,6-trichloropicolinic acid (picloram) showed the greatest inhibition and 3-amino-2,5-dichlorobenzoic acid (chloramben) the greatest stimulation of emergence force of soybean seedlings.

Seed of common ragweed (Ambrosia artemisiifolia L.) ecotypes were collected from 12 locations in North America and were planted at Ithaca, New York. Plants from seed collected in the northern latitudes flowered earlier and produced less vegetative growth. The difference in growth and development of the ecotypes was caused by the day length or latitude where they had originated. Seedlings emerging in early July produced approximately one-third as much fresh or dry weight and about one-third as many viable seeds as those emerging in the middle of May. The latter produced more than 32,000 seed per plant.

The adsorption of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) from aqueous solution by charcoal varied widely with the type of charcoal tested. However, adsorption in solution was directly related to the deactivating properties of the charcoals for the two herbicides in soil. Several charcoals deactivated residues of 0.3 ppmw of atrazine and 1.0 ppmw of diuron when they were present at concentrations of 30 to 50 ppmw in the soil. Activation of the charcoal was essential for the adsorption and deactivating properties. A simple laboratory test was developed for assessing activated charcoals for use in deactivation studies in soil.

Movement of pesticides on soil thin-layer chromatographic (TLC) plates was detected by a bioassay employing a green alga, Chlorella sorokiniana Shihira and Krauss. After leaching the soil TLC plates with water, a Chlorella suspension in an enriched agar medium was aspirated onto the soil to give ca. 8 × 106 cells/cm2. Plates were incubated at 100% relative humidity at 30 C, with illumination of ca. 40 klux. Zones of pesticide movement were visible within 24 to 48 hr. Mobility in Hagerstown silty clay loam was assessed for two methylcarbamate insecticides and for nine phenylurea, 11 s-triazine, and 13 miscellaneous herbicides. Among analogous triazines, the mobility order was: -OCH3 > -Cl > -SCH3. Movement of 6,7-dihydrodipyrido[1,2-a:2′,1′-c]pyrazinediium ion (diquat) and 1,1′-dimethyl-4,4′-bipyridinium ion (paraquat), normally immobile in soils, was directly proportional to rate when applied in high doses.

Residues in soil, following application of 0.25 lb/A of 4-amino-3,5,6-trichloropicolinic acid (picloram) to semi-arid rangelands, usually were restricted to the top 12 inches for 60 days. Five ppb or less picloram were detected below 12 inches at 120 to 180 days after application; but picloram usually dissipated from the soil profile within a year. More picloram was detected 5 months after application at 6 to 18 inches deep at the lower ends of plots with 3% slopes than in plots with 0, 1, or 2% slopes. Runoff water from plots irrigated 10 days after treatment contained 17 ppb picloram. Irrigation or rainfall at 20, 30, or 45 days after picloram application resulted in less than 1 ppb picloram in runoff water. No more than 1 or 2 ppb picloram were detected after dilution of runoff water in large ponds.

Dichlobenil (2,6-dichlorobenzonitrile), 3-tert-butyl-5-chloro-6-methyluracil (terbacil), and 3-tert-butyl-5-bromo-6-methyluracil (hereinafter referred to as DP-733) were applied annually for 3 years as soil surface or incorporated treatments for weed control in young peach (Prunus persica (L.) Batsch., var. Redhaven) trees. Average monthly ratings showed significant increases in bermudagrass (Cynodon dactylon (L.) Pers.) control with incorporation of all three herbicides. Treetrunk diameters in incorporated dichlobenil plots were greater than those in surface-applied dichlobenil plots. Incorporation in the soil reduced loss of dichlobenil, terbacil, and DP-733. The herbicides did not accumulate in the 0 to 15-cm soil layer. Low concentrations were detected in the 30 to 60-cm soil depth 1 year after the third annual application of 6.72 kg/ha of dichlobenil and 4.48 kg/ha of DP-733. Terbacil was not present in detectable amounts at 30 to 60 cm but was present in the 15 to 30-cm layer of 4.48 kg/ha plots.

Single topical applications of monosodium methanearsonate (MSMA) affected cotton (Gossypium hirsutum L.) growth more than did similar disodium methanearsonate (DSMA) applications. There was usually no difference in yield among rates and dates with single applications of DSMA. Single applications of MSMA at later dates and higher rates reduced yields. Repeated topical applications of MSMA reduced yields and affected boll weight, lint percentage, number of seed per boll, and fiber fineness as compared with these properties of cotton treated once with MSMA. Response of cotton to MSMA was related to the number of applications and rate of herbicide. Repeated applications of DSMA affected cotton yield, lint percentage, and number of seed per boll less than did MSMA.

Rapid absorption and limited acropetal movement of 14C from p-nitrophenyl-α,α,α-trifluoro-2-nitro-p-tolyl ether (hereafter referred to as fluorodifen) labeled with 14C at either the 1 position of the p-nitrophenyl ring (fluorodifen-1′-14C) or the trifluoromethyl carbon (fluorodifen-14CF3) were observed in peanut (Arachis hypogaea L., var. Starr) seedlings after root treatment for 48 hr followed by 96 hr in nutrient solution. Major products of degradation of fluorodifen-1′-14C were p-nitrophenol and Unknown I (possibly a conjugate of p-nitrophenol). Some p-nitrophenyl-α,α,α-trifluoro-2-amino-p-tolyl ether and several minor unknowns were detected. The major product of degradation of fluorodifen-14CF3 was Unknown II (possibly a conjugate of 2-amino-4-trifluoromethylphenol). Some 2-amino-4-trifluoromethylphenol and traces of p-nitrophenyl-α,α,α-trifluoro-2-amino-p-tolyl ether, p-aminophenyl-α,α,α-trifluoro-2-nitro-p-tolyl ether, p-aminophenyl-α,α,α-trifluoro-2-amino-p-tolyl ether, and several minor unknowns also were detected. A major pathway of fluorodifen degradation in peanut seedlings is postulated whereby fluorodifen is reduced to the 2-amino derivative which is cleaved at the ether linkage to yield p-nitrophenol and 2-amino-4-trifluoromethylphenol. The respective phenols are then conjugated with natural plant substances to form water soluble conjugates.

Degradation of 1,1-dimethyl-3-(a,a,a-trifluoro-m-tolyl) urea (fluometuron) in a sandy loam soil was investigated in time-course and 14CO2 evolution studies. Degradation occurred only in nonautoclaved samples and was more rapid in glucose-amended soil, indicating that it is a function of microbial metabolism. Time-course studies showed that the pathway of degradation of fluometuron in soil is similar to that previously reported for other substituted ureas, involving a two-step demethylation, probably followed by hydrolysis of the urea linkage to form the aniline derivative. Further evidence for degradation was a small but significant recovery of 14CO2 from soil treated with fluometuron labeled in the trifluoromethyl group.