Five herbicides were applied postemergence to three Louisiana sugarcane (Saccharum officinarum L.) varieties. Nine or 12 lb/A of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) severely injured varieties C.P. 44-101 and C.P. 52-68, but variety N.Co. 310 was not affected. Conversely, N.Co. 310 was injured more by 2,2-dichloropropionic acid (dalapon) than the other varieties. Trichloroacetic acid (TCA) + 2,4-dichlorophenoxyacetic acid (2,4-D) at 10.6 plus 3 lb/A, reduced the yield of variety N.Co. 310 in one of 2 years only. This treatment had no adverse effect on yields of the other two varieties. All varieties appeared tolerant to 2,3,-6-trichlorophenylacetic acid (fenac) applied at 4 to 12 lb/A. Diuron injured a sensitive variety both when the foliage was sprayed and when only the ground at the base of the cane was sprayed. Plants treated in May were injured more than those treated 30 days earlier.

Additions of montmorillonite clay and soil of high organic matter content to growth media consisting of sand and nutrient solution significantly decreased the phytotoxicity of 2-methylthio-4,6-bis(isopropylamino)-s-triazine (prometryne) to wheat [Triticum aestivum L. em. Thell. (aestivum group) “Wakeland”]. Phytotoxicity was decreased to a greater extent at pH 4.5 than at pH 6.5. The reduction in phytotoxicity was attributed to adsorption of the herbicide by the additives. A larger proportion of the prometryne was present in the protonated form at the lower pH and the increased adsorption probably resulted from the coulombic bonding of these cations to the soil additives. Adsorption mechanisms are postulated and discussed.

Golf putting greens were sprayed with N-(2-mercaptoethyl) benzenesulfonamide S-(O,O-diisopropyl phosphorodithioate) (bensulide). Creeping bentgrass (Agrostis palustris Huds.) and annual bluegrass (Poa annua L.) were observed for injury. Preemergence and postemergence treatments of 5-bromo-3-sec-butyl-6-methyluracil (bromacil), 5-chloro-3-tert-butyl-6-methyluracil (terbacil), and 5-bromo-3-tert-butyl-6-methyluracil (hereinafter referred to as DP 733) were applied to a prepared seedbed planted with Kentucky bluegrasses (Poa pratensis L., var. Merion and var. Newport) and annual bluegrass.

Thirty lb/A of bensulide produced leaf discoloration and root length reduction of established annual bluegrass plants without injuring creeping bentgrass. Terbacil at 0.2 lb/A and bromacil at 0.4 lb/A gave highly selective control of annual bluegrass in Merion and Newport Kentucky bluegrasses when applied preemergence to the three grasses. Postemergence applications of these compounds produced moderate selective control of annual bluegrass.

A tractor-mounted mist blower was as effective as a high-volume ground sprayer or an airplane sprayer for applying herbicides to control hardwoods in two tests in central Louisiana. Two lb/A of butoxyethanol ester of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) were slightly better than one, and May treatments were more effective than August treatments.

Greenhouse and field studies showed that α,α,α,-trifluro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) gave better control of wild cane [Sorghum bicolor (L.) Moench] when incorporated in the soil above rather than below the wild cane seed. Of four herbicides studied in field experiments, trifluralin gave the best control of wild cane in soybeans (Glycine max L., var. Clark) followed by S-propyl dipropylthiocarbamate (vernolate). Herbicides were more effective than cultivation in controlling wild cane, but neither alone was adequate. A combination of cultivation plus herbicides markedly increased soybean yields on wild cane infested areas. These results show that an economical crop of soybeans can be produced on wild cane infested land.

An assay technique utilizing Chlorella vulgaris Beijerinck gave highly significant responses to low concentrations of aqueous 3-(p-chlorophenyl)-l,l dimethylurea (monuron), 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), and 2,4-bis(isopropylamino)-6-methylmercapto-s-triazine (prometryne) following 6 days of incubation. Water extracts of diuron from soil assayed with this organism were highly correlated with diuron added to the soil. Similar correlations for oats (Avena sativa L.) grown on the soil and for diuron in the water extracts as dichloroaniline serve to substantiate the relative effectiveness of the method. Assay of soil samples from field residue plots taken 150 days after herbicidal application showed that active residues of diuron and prometryne were detectable by the organism. Although the chemical method was faster, it has the disadvantage of measuring any dichloroaniline residues rather than only the active residues. The method developed insures a considerable saving in time over herbicide assays involving higher plants and gives reasonably good quantitative data on low concentrations of toxic monuron, diuron, and prometryne.

Highbush blueberries [Vaccinium australe (Small), var. Colville] grown on a Leon sand at Chatsworth, New Jersey were treated with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) and 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) each spring or each spring and fall from 1960 through 1966. The weed control obtained with diuron generally improved with continued use. At rates of simazine sufficient to achieve satisfactory control, the degree of weed control increased for the first 3 years and decreased the last 3 years. Diuron and simazine at rates sufficient to provide satisfactory weed control did not reduce the productivity of the blueberry plant. Palatability evaluations of off-flavor and sweetness of frozen blueberries, and objective measurements of pH and soluble solids, indicated that the diuron and simazine treatments did not affect any of these quality factors.

Leaf discs of cotton (Gossypium hirsutum L.), broadleaf plantain (Plantago major L.), soybeans (Glycine max Merrill), and corn (Zea mays L.) were incubated 1 hr in aqueous solutions of methyl- or ring-labeled 3-(p-chlorophenyl)-l,l-dimethylurea-14C (monuron) or carbonyl-labeled 3-(3,4-dichlorophenyl)-l,l-dimethyl-urea-14C (diuron). The loss of herbicide and formation of metabolites were determined at approximately 1-hr intervals up to 7 hr. Cotton leaf discs actively metabolized monuron to l-(p-chlorophenyl)-3-methylurea (monomethylmonuron), l-(p-chlorophenyl)urea (p-chlorophenylurea), and p-chloroaniline. Plantain leaf discs strongly metabolized diuron to l-(3-,4-dichlorophenyl)-3-methylurea (monomethyldiuron) and l-(3,4-dichlorophenyl)urea (3,4-dichlorophenylurea). Plantain degraded monuron less actively than diuron and cotton degraded diuron less rapidly than monuron. In soybean leaf discs, metabolism did not progress beyond the first demethylation, and corn leaf discs were unable to metabolize the herbicides in short-term studies.

In greenhouse experiments, soil-incorporated combinations of 0,0-diethyl S-[2-(ethylthio)-methyl]-phosphorodithioate (phorate) or 0,0-diethyl S-[2-(ethylthio)-ethyl]-phosphorodithioate (disulfoton) with a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) resulted in increased cotton (Gossypium hirsutum L.) seedling growth as compared to trifluralin used alone. This result apparently was due to the greater numbers of secondary roots in the zone of incorporation. Phorate was more effective than disulfoton in overcoming the inhibitory effect of trifluralin on secondary root development. A comparison of granular and emulsifiable phorate showed no advantage for either formulation. The combination of phorate and trifluralin in a 1-inch soil core, into which seeds of cotton were planted and surrounded by trifluralin-treated soil, also increased secondary root development as compared to using trifluralin alone.

Preliminary field experiments with 3,4-dichloropropionanilide (propanil) indicated that methods of application had little effect on the activity of this herbicide. Growth of tomato (Lycopersicum esculentum Mill.) plants was reduced for about 7 days. Susceptible plants were killed in 3 to 7 days. Propanil inhibited the growth of tomato radicles and the auxin-induced growth of Avena coleoptiles. Propanil destroyed the permeability of red beet (Beta vulgaris L.) membranes and also destroyed chloroplast membranes in vitro. Oxygen uptake by isolated mitochondria and treated leaf tissues, and phosphate esterification in mitochondria were severely inhibited by propanil. Photosynthesis was completely inhibited within 20 min after treatment but began to return to normal in resistant plants (tomato) after 6 hr.

At rates as high as 40 lb/A, 1-(2-methylcyclohexyl)-3-phenylurea (siduron) did not reduce the growth of crabgrass (Digitaria spp.) seedlings although it was highly toxic to germinating seeds. Siduron placed at the 2-inch soil depth reduced root growth but not shoot growth of crabgrass. Barley (Hordeum vulgare L., var. Trail) roots, like crabgrass, were more affected than shoots. Carbonyl labeled siduron-14C was absorbed by both barley roots and shoots. Siduron-14C was translocated from roots to shoots but not from shoots to roots. Analysis of the extracts from plants treated at various times revealed that no metabolites of siduron-14C were present. Siduron must be present at the time of seed germination to effectively reduce plant growth.

Persistence and movement of 2,3,6-trichlorobenzoic acid (2,3,6-TBA) in a silty clay loam soil was studied. Single applications of 16 lb/A 2,3,6-TBA were made to field plots on 21 dates from 1955 to 1965. All treated plots were sampled to a depth of 8 ft in 1966, and a few were sampled to a depth of 11 ft. One-foot increments of soil were bioassayed to determine presence of the herbicide. Variation in amount and depth of penetration of 2,3,6-TBA was noted, but the herbicide had persisted in the soil 11 years. Persistence and movement could not be related to moisture before or after treatment, temperature after treatment, or, except for treatments applied in 1964 and 1965, time between treatments and sampling. Residues from fall applications appeared to be slightly greater than those from spring or summer applications.

S-ethyl hexahydro-1 H-azepine-l-carbothioate-C14 (molinate-C14) applied to the leaves of barnyardgrass [Echinochloa crusgalli (L.) Beauv.] and rice (Oryza sativa L.) was predominantly translocated acropetally. Root-applied molinate-C14 was translocated readily throughout the plant. Excised organs of barnyardgrass absorbed more molinate-C14 than did corresponding organs of rice. With surface application, injury by 5 or 10 ppm molinate to rice planted at depths of 0, 0.5, 1.0, or 1.5 in decreased with increasing depth of planting, but injury increased in incorporated treatments with increasing depth of planting. Barnyardgrass was markedly suppressed at all depths of planting. Inhibition of elongation of barnyardgrass by molinate was overcome by an equimolar concentration of gibberellic acid. Molinate reduced the level of soluble RNA in barnyardgrass coleoptiles.

Uptake and translocation of 14C label from S-2,3-dichloroallyl N,N-diisopropylthiolcarbamate (diallate) by roots and coleoptiles of wild oat (Avena fatua L.), wheat (Triticum aestivum L., var. Selkirk), barley (Hordeum vulgare L., var. Traill), and flax (Linum usitatissimum L., var. Bolley) were compared. The pattern of 14C label uptake and movement was similar in wild oat, barley, and wheat. However, translocation of the 14C label to the roots of wild oat was less than for barley. Although differential uptake and translocation per se did not appear to account for the selectivity of diallate for wild oat, some differences in translocation may have beep the result of metabolic breakdown products.

Two field experiments were conducted to determine the soil persistence, crop toxicity, and effectiveness of four herbicides in controlling purple nutsedge (Cyperus rotundus L.). Excellent control of purple nutsedge was obtained with 2,6-dichlorobenzonitrile (dichlobenil) and good control was obtained with N-hydroxy-methyl-2,6-dichlorothiobenzamide. Both 3-iert-butyl-5-chloro-6-methyluracil (terbacil) and 5-bromo-3-teri-butyl-6-methyluracil were effective in controlling purple nutsedge, but maximum control was not obtained until 9 to 12 months after these chemicals were incorporated in the soil. Toxicity of all chemicals to beans (Phaseolus vulgaris, var. humilis L., Blue Lake), corn (Zea mays var. rugosa L., Golden Security), summer squash (Cucurbita moschata Duchesne, var. Yellow Crookneck), tomato (Lycopersicum esculentum Mill., var. Flora-del), and gladiolus (Gladiolus hortulanus Bailey, var. Friendship) increased as the rates were increased and decreased with time after treatment. Infestation of purple nutsedge from escaping tubers increased as the herbicidal persistence decreased.

Sublethal concentrations of isopropyl N-(3-chlorophenyl)- carbamate (CIPC) labeled with 14C in the ring or side chain were applied to all leaves present or to the roots of redroot pigweed (Amaranthus retroflexus L.), pale smartweed (Polygonum lapathiofolium L.), and parsnip (Pastinaca sativa L.). These species were selected because of their different susceptibilities to CIPC. The herbicide did not move out of the treated leaves in pigweed and smartweed and only slightly in parsnip in 21 days. In root treatment (3 days), the herbicide moved to all plant parts and the extent of movement was essentially the same in all species. Water soluble metabolites, which differed in Rf values were extracted from all three species. The metabolites apparently were not the result of cleavage of the CIPC molecule, but were more likely conjugates of CIPC with natural plant component(s). Very little 14CO2 was released by any of the species in 3 days. These data indicate that differences in movement and metabolism are not sufficient to account for the different susceptibilities of these three plant species.

Eight technically pure herbicides were evaluated for their relative phytotoxicity to hydroponically grown seedlings of red maple (Acer rubrum L.) and white ash (Fraxinus americana L.). Six of the herbicides (acids) were prepared as the triethylamine salts to provide formulation uniformity. With four compounds, equi-mole dosages per plant produced different toxic responses depending upon whether the herbicide was applied to the shoot or root. The 2,4,5-trichlorinated phenoxyaliphatic acids 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), 2(2,4,5-trichlorophenoxy) propionic acid (2,4,5-TP), and 4(2,4,5-trichlorophenoxy) butyric acid (2,4,5-TB) were consistently more toxic on a mole basis when applied to the roots of both species than when applied to the shoots. The opposite effect was observed with ammonium sulfamate (AMS) where shoot treatments were always more toxic. Shoot and root treatments were equally effective for the compounds 2,4-dichlorophenoxyacetic acid (2,4-D), 2-methoxy-3,6-dichlorobenzoic acid (dicamba), 4-amino-3,5,6-trichloropicolinic acid (picloram), and 3-amino-l,2,4-triazole (amitrole). Differential species susceptibilities to certain compounds were observed.

A study of herbicides to aid in establishing an Emerald zoysia (Zoysia japonica x Zoysia tenuifolia Willd. ex Trin.) sod was initiated in the summer of 1965. Eleven herbicides were applied to Emerald zoysia sod-plugs newly planted in Emory clay loam soil. All of the herbicides provided excellent premergence control of crabgrass (Digitaria spp.) and goosegrass (Eleusine indica (L.) Gaertn.) throughout the growing season following treatments. Both 1-(2-methylcyclohexyl)-3-phenylurea (siduron) and O-(2,4-dichlorophenyl) O-methyl isopropylphosphoramido-thioate (DMPA) caused either no observable injury or only slight injury, thus causing no apparent chemical inhibition of growth and resulting in a rapid rate of establishment of the turfgrass. But N-(2-mercaptoethyl)benzenesulfonamide S-(O,O-diisopropyl phosphorodithioate) (bensulide) and 2,6-di-tert-p-tolyl-methylcarbamate (terbutol) severely injured Emerald zoysia; they seriously retarded the growth of the zoysia and greatly inhibited ground cover. Herbicides which effectively eliminated weed competition but which greatly retarded the growth of the turfgrass were more detrimental to establishment rate than the actual competition from weeds. These results indicate that selecting a herbicide safe to the turfgrass is more important than choosing a herbicide which only gives good weed control. However, indications are that some herbicides do combine the two important factors of safety and excellent weed control.

The prolificacy of honeyvine milkweed [Ampelamus albidus (Nutt.) Britt.] was investigated. Mature seeds stored at 0, 10, and 24 C and germinated at 32 C demonstrated high viability from harvest to 1 year old. Immature seeds were slightly less viable but followed the same trends in germination. Studies with rhizomes excavated at four different times throughout the year showed that segments 1 inch long with at least one live bud were capable of generating regrowth. These reproductive characteristics with the inherent tenacity of honeyvine milkweed indicate a potentially serious weed problem in many agricultural regions of the United States.

Growth of Salmonella typhimurium LT-2 (Loeffler) Cast. and Chalm. was inhibited by 3-amino-l,2,4-triazole (amitrole), and 3-hydroxy-1,2,4-triazole, 3-chloro-l,2,4-triazole, and 5-amino-1,2,3,4-tetrazole (hereinafter referred to respectively as hydroxytriazole, chlorotriazole, and aminotetrazole). Toxicity of 2 × 10−2 M amitrole was partially overcome by 2 × 10−4 M histidine, and more effectively circumvented by combinations of histidine with 2 × 10−4 M adenine, 2 × 10−4 M riboflavin, or 2 × 10−4 M methionine. Serine reduced toxicity of 10−1 M amitrole when combined with both histidine and adenine but was less effective than methionine. Hydroxytriazole inhibition was partially overcome by adenine or less effectively by histidine but not by riboflavin, methionine, or serine. Chlorotriazole and aminotetrazole inhibitions were circumvented by 2 × 10−4 M methionine, 10−3 M serine, and 10−4 M cysteine but not by histidine, adenine, or riboflavin. The toxicity of high concentrations (10−3 M) of cysteine was reduced by chlorotriazole and aminotetrazole.