Greenhouse and field studies were conducted to compare the phytotoxicity of HOE 23408 {methyl 2-[4-(2,4-dichlorophenoxy)phenoxy]-propanoate} to several crops and annual grass weeds, and to determine the herbicides's soil mobility and persistence. In general, the order of susceptibility of 13 seedling grassy weeds remained constant, whether the herbicide was applied preplant incorporated, pre-emergence, or postemergence. The herbicide was most phytotoxic when it was applied either preplant incorporated or early postemergence. Grain sorghum [Sorghum bicolor (L.) Moench ‘BR-54′] and oats (Avena sativa L. ‘Cimarron’) were moderately susceptible to HOE 23408, whereas barley (Hordeum vulgare L. ‘Will’) exhibited marginal tolerance. Wheat (Triticum aestivum L. ‘Triumph 64′) and cotton (Gossypium hirsutum L. ‘Westburn 70′) showed tolerance to HOE 23408 at rates up to 6 ppmw, and soybean [Glycine max (L.) Merr. ‘Bragg’] and peanut (Arachis hypogaea L. ‘Spanhoma’) demonstrated tolerance to concentrations as high as 24 ppmw. The soil mobility of HOE 23408 was similar to that of trifluralin (a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine). No soil phytotoxicity was found 8 weeks after herbicide application in the field or under laboratory incubation conditions of 5 or 10% soil moisture at 21 C. Dissipation was much slower at a temperature of 4.4 C, regardless of the soil moisture level.

The distribution of simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] in whole plants and the effect of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] on isolated leaf cells and chloroplasts of two biotypes of common groundsel (Senecio vulgaris L.) were studied. Both biotypes accumulated 14C at the leaf margins 60 hr after exposure of roots to 14C-simazine. No difference in herbicide distribution between the two biotypes was observed. Atrazine (10 μM) inhibited photosynthesis, RNA synthesis, and lipid synthesis in isolated susceptible (S) cells but not resistant (R) cells. Lipid synthesis in S cells but not R cells was enhanced by exposure to 1 and 0.1 μM atrazine for 1 hr. Photochemical activity of R chloroplasts was not inhibited by atrazine but S chloroplasts were severely inhibited.

Corn (Zea mays L.) was grown in EPTC-(S-ethyl dipropylthiocarbamate) and butylate-(S-ethyl diisobutylthiocarbamate) treated soil at 33 and 15% moisture in growth chambers at 30 and 20 C. EPTC (6 and 18 ppm) and butylate (19 and 50 ppm) reduced corn growth more at 30 than at 20 C. The days before emergence of the corn coleoptile were the most critical time for thiocarbamate injury. When plants were grown at 30 C before emergence more injury occurred at 33% soil moisture than at 15% except with butylate at 19 ppm. At 20 C, however, plants grew as tall or taller at 33% soil moisture than at 15% except for butylate at 19 ppm. Addition of R-25788 (N,N-diallyl-2,2-dichloroacetamide) to EPTC and butylate increased by about 10 times the amount of herbicide required to injure corn. With R-25788 the toxicity of these two herbicides was not influenced greatly by either temperature or soil moisture.

Glyphosate [N-(phosphonomethyl)glycine] was applied to selected areas on young apple (Malus sylvestris L.), pear (Pyrus communis L.), sour cherry (Prunus cerasus L.), and peach [Prunus persica (L.) Patsch] trees to observe tree response. Injury occurred only on newly planted peach when contact was made on the basal 12.7 cm of tree trunks. Glyphosate effectively killed suckers without damaging trees. When sprays were applied to a lower branch of apple trees, local injury occurred the same season and the following year, but symptoms were not visible in other portions of the tree. Radiolabeled glyphosate was applied to the basal trunk, leaves, suckers, and fruit of 4-yr-old ‘MacSpur’/MM106 apple and 5-yr-old ‘Bartlett’/seedling pear. Applications on basal trunk areas produced no detectable radioactivity in leaves, buds, or fruits at harvest time. Applications on sucker leaves produced radioactivity only in the treated and adjacent sucker tissue and not in other portions of the tree. The 14 C-glyphosate moved readily from the treated leaves of lower branches to other leaves, buds, and developing fruit on the same branch but was not detectable in other areas of the tree. After 90 days, 92 to 98% of the extractable radioactivity in leaf, bud, or fruit tissue was unaltered 14 C-glyphosate.

A survey determined the extent and severity of the infestations of four species of Carduus thistles in the United States. In the mainland United States, 360 counties of 3068 have economically important infestations of musk thistle (Carduus nutans L.), the Appalachian and midwest regions harboring the greatest infestations. Plumeless thistle (Carduus acanthoides L.) and Italian thistle (Carduus pycnocephalus L.) are of economic importance, but have limited distribution. Welted thistle (Carduus crispus L.) is approaching pest status only in Virginia.

Several dozen herbicide systems were evaluated over a 4-yr period for weed control in stubble no-till planted corn (Zea mays L.). Crop tolerance and corn yield data also were obtained. Paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) and glyphosate [N-(phosphonomethyl)glycine] afforded excellent desiccation of all emerged vegetation each year. The oil-soluble formulation of dinoseb (2-sec-butyl-4,6-dinitrophenol) also afforded complete contact control of emerged vegetation in 1975, the only year it was evaluated. A herbicide system consisting of an acetanilide plus a triazine afforded the most consistent residual weed control. The specific herbicides affording satisfactory control largely depended on the weed spectrum. Fall panicum (Panicum dichotomiflorum Michx.), large crabgrass [Digitaria sanguinalis (L.) Scop.], and yellow nutsedge (Cyperus esculentus L.) were the weeds most difficult to control with the herbicide systems used in these studies. Corn yields were influenced primarily by the degree of weed control achieved, and in several instances by secondary effects of stand reduction or injury.

Johnsongrass [Sorghum halepense (L.) Pers.] was grown for 4, 8, and 12 weeks at 24, 32, and 40 C at 9, 13, and 19 klux illumination. Maximum growth and development after 12 weeks were obtained at 32 C and 19 klux. Maximum leaf growth and development were obtained at 32 C and 9 klux. Primary culm height and weight were greater at 24 C than at 40 C, regardless of the illumination, whereas secondary culm height and weight were greater at 40 C than at 24 C. Secondary culm production increased at 40 C and decreased at 24 C. Root and rhizome development increased with increasing light intensity. Growth of roots and rhizomes was maximum at 32 C and minimum at 40 C.

Seeds of wild safflower (Carthamus oxyacantha Bieb.) collected from the Bajgah area, Iran, in 2 successive years were subjected to stratification and scarification treatments and their germination percentage and subsequent seedling growth (length) were measured at room temperature (23 ± 2 C). Maximum germination and seedling length occurred in the seeds stratified in moist sand at 4 C for 2 weeks. The response of the freshly-harvested seed to scarification was linear while that for 1-yr-old seed was quadratic. Both scarification and stratification independently increased germination but germination never reached the viability level of the seed.

A ‘tifgreen’ bermudagrass [Cynodon dactylon (L.) Pers.] golf-type green was treated with seven preemergence and one postemergence type herbicides at two rates each for three consecutive years to assess their phytotoxicity. A few herbicides were applied on a second, third, and fourth treatment date during the year with applications made in separate plots. Severe foliage injury occurred the first year with siduron [1-(2-methylcyclohexyl)-3-phenylurea] while moderate injury occurred with bromacil (5-bromo-3-sec-butyl-6-methyluracil) and DCPA (dimethyl tetrachloroterephthalate); and slight injury occurred with benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine), bensulide [0,0-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl)benzenesulfonamide], and terbutol (2,6-di-tert-butyl-p-tolyl methylcarbamate). No injury was observed with bandane (polychlorodicyclopentadiene isomers) and tri-calcium arsenate. Injury to the bermudagrass in the second year following renewal treatments was severe with siduron and bromacil; moderate with benefin, bandane, DCPA, and terbutol; and slight with bensulide and tri-calcium arsenate. Injury in the third year following repeat applications was severe with siduron, terbutol, bandane, bromacil, benefin, and DCPA; slight to moderate with bensulide, and slight with tri-calcium arsenate. Injury observed the fourth year resulting from residues was moderate with bandane; slight with terbutol, benefin, bensulide, and DCPA; and none with siduron, bromacil, and tri-calcium arsenate.

The sorption equilibria and relative mobility of metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] were evaluated on 16 soils from the lower alluvial flood plain of the Mississippi River as a function of soil properties. Metribuzin sorption and mobility were significantly correlated with each other and both parameters were significantly associated with clay content, organic matter, and water content at 0, 0.33 field capacity (FC), and 15 bars tension. Prediction equations for adsorption (K1 = −1.10 + 0.08 FC) and mobility (Rf = 0.81 − 0.015 FC) indices were developed based on water content at 0.33 bar tension (FC). A competitive effect was observed between the combination of various levels of clay and organic matter as related to metribuzin adsorption.

Five crops were grown for three seasons following a single soil-incorporated application of MSMA (monosodium methanearsonate). Crop sensitivity to soil arsenic decreased as follows: snap beans (Phaseolus vulgaris L. ‘Early Gallatin’ and ‘Tenderette’); rice (Oryza sativa L. ‘Dawn’ and ‘Starbonnet’); soybeans [Glycine max (L.) Merr. ‘Lee 68′]; potatoes (Solarium tuberosum L. ‘Red LaSoda’ and ‘Red Pontiac’); and cotton (Gossypium hirsutum L. ‘Stoneville 7A’). Over the 3-yr period, yield of snap beans was reduced 8, 14, and 85% below the untreated check where MSMA had been incorporated initially at 22, 45, and 269 kg/ha, respectively. Similar reductions in yield of rice were 18, 25, and 55%. Soybean and potato yields were significantly reduced only at the highest rate of MSMA while cotton yields were unaffected. Arsenic content in the edible portion of the crops decreased as follows: rice, snap beans, potatoes, soybeans, and cotton. The arsenic content in crops from the highest MSMA plots seldom exceeded twice that from the untreated plots.

Six species of Solanaceae including tomato (Lycopersicon esculentum Mill ‘Campbell 28′) were sprayed in the greenhouse at weekly intervals for 4 weeks starting when tomato plants had one true leaf. All species gained tolerance to metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one] with age but tomato and black nightshade (Solarium nigrum L.) were the most tolerant and gained tolerance fastest with age. Jimsonweed (Datura stramonium L.) and eggplant (Solanum melongena L. ‘Black Beauty’) were the most susceptible species and the ones that gained least tolerance with age. Potato (Solanum tuberosum L.) from true seeds and pepper (Capsicum annuum L. ‘Yolo wonder’) were intermediate in tolerance. In the field, tomato and nine weed species planted in separate plots and kept free from competition were sprayed at weekly intervals starting when tomato plants had one true leaf. Tomato, large crabgrass (Digitaria sanguinales (L.) Scop.), ivyleaf morningglory (Ipomoea hederaceae (L.) Jacq.) and yellow foxtail (Setaria glauca (L.) Beauv.) were the most resistant species to metribuzin and the ones that gained tolerance fastest with age. The most susceptible weeds were velvetleaf (Abutilon theophrasti Medic), common purslane (Portulaca oleracea L.), pale smartweed (Polygonum lapathifolium L.), redroot pigweed (Amaranthus retroflexus L.), common lambsquarters (Chenopodium album L.), and jimsonweed. Low amounts of sunlight during the 3 days before spraying greatly reduced the resistance of tomato to metribuzin.

Alachlor [2-chloro-2′,6′-diethyl-N(methoxymethyl)-acetanilide], propachlor (2-chloro-N-isopropylacetanilide) and prynachlor [2-chloro-N-(1-methyl-2-propynyl)acetanilide], inhibited gibberellic acid (GA3),-induced production of protease and α-amylase in deembryonated barley (Hordeum vulgare L, ‘Schuyler’) seed. Production of protease was more sensitive to these herbicides than α-amylase. The degree of inhibition of protease and α-amylase production caused by alachlor was equivalent to that caused by cycloheximide, puromycin and actinomycin-D, known protein and nucleic acid synthesis inhibitors. Higher GA3 concentrations reversed the inhibition of protease and α-amylase synthesis caused by alachlor but did not reduce the effect of alachlor on barley seed germination and growth. It is concluded that the inhibition of protease and α-amylase production by alachlor is perhaps only one of several effects on early seed germination and seedling development.

Betacyanin efflux from “aged” red beet (Beta vulgaris L.) root tissue, measured spectrophotometrically, was increased as temperature and EPTC (S-ethyl dipropylthiocarbamate) concentration increased. Acetate-2-14C (∗Ac) incorporation into the total fatty acid content was inhibited by EPTC. EPTC inhibited the incorporation of ∗Ac into the dienoic fatty acids and NA (1,8-naphthalic anhydride) reversed the EPTC induced inhibition of the incorporation of ∗Ac into dienoic fatty acids.

A great deal of energy in recent months has been expended in worrying about energy. The procurement, allocation, utilization, and conservation of energy sources have been probed countless times and viewed from almost every possible vantage point. The word “energy” now shares the stage with the word “environment.”

The aerobic rate of disappearance of isopropalin (2,6-dinitro-N,N-dipropyl-cumidine) was slower than that of oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide) in soil. The aerobic half-lives for isopropalin were 3.5 months and 13.3 months and for oryzalin 1.40 months and 4.35 months at 30 and 15 C respectively. A simple system was devised to create anaerobiosis in soil at 80% of field capacity. Both herbicides dissipated more rapidly under anaerobic conditions. The first order half-lives at 30 C in anaerobic soil were 0.17 months for isopropalin and 0.34 months for oryzalin. Neither first, second, nor half order kinetics were clearly superior in describing the degradation processes. Arrhenius activation energies suggested that the degradation processes were non-biological.

The influence of several factors on the injury to corn (Zea mays L.) seedlings from high rates of EPTC (S-ethyl dipropylthiocarbamate) + R-25788 (N,N-diallyl-2,2-dichloroacetamide) was determined in growth chambers. This herbicide combination severely injured 6% of the corn seedlings at rates as low as 14 ppm if the herbicide was poorly incorporated into the soil. If thoroughly incorporated, severe injury did not occur unless the rate of application exceeded 56 ppm. Decreased injury resulted when seed were placed so as to insure rapid shoot emergence. Seed planted at 2 cm with its coleoptile pointed upward or horizontally (with posterior facing upward) was injured less than in other positions, Corn cultivars differ in their susceptibility to EPTC + R-25788 at 30 but not at 20 C. Of the several corn cultivars tested at 30 C, SX-98 was the least injured by EPTC + R-25788. Corn injury was progressively reduced as leaching volumes were increased and as the time from herbicide application to corn planting was increased.