The herbicide 2,4,5-T [(2,4,5-trichlorophenoxy) acetic acid], at concentrations of 10−4 and 10−6 M in nutrient media, was more inhibitory to the growth of soybean (Glycine max (L.) Merr. “Acme”) tissue culture than dicamba (3,6-dichloro-o-anisic acid) or picloram (4-amino-3,5,6-trichloropicolinic acid). Dicamba (10−6 and 10−8 M) and 2,4,5-T (10−8M) stimulated growth of soybean tissue. Mixing equimolar solutions of 2,4,5-T + dicamba, 2,4,5-T + picloram, or picloram + dicamba at 10−4, 10−6, and 10−8 M did not increase phytotoxicity over that of the most phytotoxic herbicide of the pair.

Injury to corn (Zea mays L.) hybrids from butylate (S-ethyl diisobutylthiocarbamate) was investigated as a function of planting depth, soil pH, and temperature. Field and growth chamber studies indicated that the potential for butylate injury increased with increasing planting depth regardless of hybrid. Greenhouse and growth chamber experiments suggested that as soil pH decreased butylate injury increased, depending upon the hybrid. Butylate injury was also a differential response among hybrids, depending on temperature. Certain hybrids may be injured more at higher temperatures and other hybrids more at lower temperatures. Butylate injury to corn, therefore, appears to be due to a three-way interaction, stress x hybrid X butylate.

Nontoxic concentrations of 2,4-D [(2,4-dichlorophenoxy)acetic acid] increased the toxicity of ametryne [2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine], when applied to the roots of waterhyacinth [Eichornia crassipes (Mart.) Solms], when applied to the roots or foliage of corn (Zea mays L.), and to a lesser extent, when applied to the roots of soybean [Glycine max (L.) Merr.]. Nontoxic concentrations of 2,4-D frequently also increased the absorption of ametryne, water, and radioactive calcium by all three species. Mixtures containing toxic concentrations of 2,4-D with ametryne were not synergistic and sometimes the mixtures were less toxic than ametryne alone. Toxic concentrations of 2,4-D also decreased plant dry weight and the absorption of ametryne, water, and calcium. Low concentrations of ametryne increased the absorption of water and sometimes calcium while high concentrations decreased dry weight and the absorption of water and calcium.

Fresh and stored dandelion (Taraxacum officinale Weber) seeds were studied to determine the germination response to a range of constant and alternating temperature regimes on thermogradient plates. Germination was initiated over a wide range of temperatures. Maximum germination of fresh seed occurred at an alternating temperature of 20 C for 16 hr and 10 C for 8 hr. Seed stored for 30 days germinated best at 20 C for 16 hr and 15 C for 8 hr. In addition to the shift in germination requirement, dormancy increased during the 30-day storage, especially at −15 C.

Pronamide [3,5-dichloro-N-(1,1-dimethyl-2-propynyl)benzamide] was applied to newly sprigged centipedegrass [Eremochloa ophiuroides (Munro) Hack.] in field and greenhouse experiments at 0.56, 0.84, 1.68, and 3.36 kg/ha at various time intervals from 0 to 10 weeks after sprigging. Sequential pronamide treatments of 0.84 kg/ha applied at sprigging followed with 1.68 kg/ha at 3 weeks after sprigging did not affect plant survival and controlled large crabgrass [Digitaria sanguinalis (L.) Scop.] and goosegrass [Eleusine indica (L.) Gaertn.] sufficiently to allow optimum growth of the turfgrass. Plots treated with one pronamide application did not control weeds satisfactorily, while more than two applications either caused turf injury or generally offered no advantage in weed control when compared with sequential 0.84 and 1.68 kg/ha treatments. In field plots treated with 0.84 kg/ha at sprigging and 1.68 kg/ha at 3 weeks after sprigging, the turf ground cover was 66% after the first growing season. Plant and root growth were not adversely affected in greenhouse-grown turf receiving similar treatments.

Maturation rate, pod production, and density of common milkweed (Asclepias syriaca L.) were determined at sites in east-central Missouri. Emergence of milkweeds in May was followed by blooming of flowers in late June, production of full-size follicles (average of 5.1 per plant) by late July, and release of seed in mid-September. Density was 1 to 3 plants per m2 and spacing of plants in 1.4 m2 samples was equidistant. Significant. positive correlations were found between mean height of milkweeds and pH, magnesium and calcium concentrations in the soil, and between density and pH of the soil.

Time of coleorhiza emergence through the per carp of sorghum [Sorghum bicolor (L.) Moench ‘AKS 614′] germinated on blotters in the dark was not affected by 1, 5, or 25 ppmw of alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl) acetanilide], by 2% w/w 1,8-naphthalic anhydride (hereafter referred to as NA) seed treatment, or their combinations. Coleoptile emergence was delayed slightly by NA alone and in combination with alachlor, but not by alachlor alone. Emergence of the primary leaf from the coleoptile was inhibited by alachlor treatments in the presence of NA and even more so in its absence. Various degrees of leaf distortion resulted when plants not exhibiting leaf emergence were placed in light. Severity of distortion was less with 1 ppmw of alachlor than with 5 ppmw, and the alachlor-induced distortion was less when in combination with 150 ppmw of NA. After 4 weeks the primary leaves were still distorted, but subsequent emerging leaves were normal in all treatments. More complete emergence and unrolling of the primary leaf were observed when terminal segments (3.5 cm long, including the coleoptile and part of the first internode) from plants grown in the presence of 150 ppmw of NA were vacuum infiltrated with 15, 25, and 50 ppmw of alachlor than in the controls. From these results we conclude that the protective action of alachlor is of a physiological nature and not one of physical deactivation of the herbicide.

Extracts from the roots and shoots of tobacco (Nicotiana tabacum L. ‘Kentucky 14′) seedlings treated with 14C-pebulate (S-propyl-1-14C butylethylthiocarbamate) were separated into various organic and aqueous phases to determine the distribution of 14C. In the roots the organic acid-carbohydrate fraction became the most highly labeled fraction with time while in the shoots the fraction containing the sterol esters and oligoglycerides was the most highly labeled early in the treatment period but gradually lost radioactivity at later time intervals. Pebulate was not recovered in detectable amounts in either the leaves or roots.

Pesticide drift studies were conducted in which two formulations were sprayed simultaneously to eliminate meteorological differences. One formulation was traced with Brilliant Sulfo Flavine (BSF) dye and the other with Rhodamine B (RhB) dye. Combined drift from both formulations was caught downwind on Mylar sheets. A filter fluorometer was used to analyze the deposits. By proper selection of a light source, primary filters, and secondary filters, the BSF was excluded while the RhB was analyzed, and vice versa. Concentrations below 1.0 μg/L were accurately measured.

Metham (sodium methyldithiocarbamate), applied alone or in combination with dichlobenil (2,6-dichlorobenzonitrile) in foam, was effective in killing roots of eucalyptus (Eucalyptus camaldulensis Dehnhardt) or willow (Salix hindsiana Benth.). An air-aqueous (19 to 1) foam of these herbicides was at least 20 times as effective as the aqueous mixture alone. Killing of the root with metham was rapid and extended above the lower treated portion, with the extent of necrosis resulting from translocation of the herbicide varying with concentration of metham that was used. The amount of the root killed with dichlobenil was limited to the treated area regardless of concentration. Four weeks were required to control the larger roots. Root killing with metham proceeded via both the aqueous and vapor phases. Results from labeling trees with 14C-assimilates indicated that neither translocation nor accumulation were greatly affected by metham or dichlobenil except in the tissues actually killed. However, transport and accumulation into untreated roots were reduced for a few weeks by dichlobenil. Similar results were obtained with cotton (Gossypium hirsutum L. ‘Acala’) treated with dichlobenil.