Greenhouse benches and pots were specially designed to facilitate herbicide research on plants. Four 0.8-cm risers were added to the bottom of polyethylene pots to improve drainage after subirrigation or surface watering. A rule die was made to punch out paper discs needed to cover the holes in the bottom of the pots to prevent soil loss during watering or drainage. Flat, level greenhouse tables with a 3-cm hinged side around the edges, were covered with 2-mm polyethylene sheeting to facilitate water retention when the side was in the up position during subirrigation and subsequent drainage of water when the side was down. Much time was saved and the soil was watered more uniformly by this system. Economics dictated discarding pots after herbicide experiments rather than incurring the expense of washing them and risking contamination of subsequent experiments.

Considerable concern and confusion exists regarding the problem presented by the present occurrence and potential spread of halogeton (Halogeton glomeratus) (M. Beib) (C. A. May) in the United States. It is now 18 years since this weed was first found near Wells, Nevada. Since that time the plant has been reported from a broad region extending from Lassen county, California to the southern edge of Montana.

Mortality rates of Geyer larkspur (Delphinium geyeri Greene), a poisonous plant, were determined after spraying with (2,4-dichlorophenoxy)acetic acid at various stages of plant development in 1967 to 1969. Sprays of 2,4-D at 2.2 kg/ha were more effective at early than at late stages of development, but seldom exceeded 40% mortality. Uneven-aged stands and early drying (dormancy) of small non-flowering plants often prevented the exposure of all plants to a single application of spray; treated plants contorted but continued growth for 5 to 8 weeks after spraying; residual seed provided a source of new plants; and previously dormant rootstock buds gave rise to new shoot and root growth the year after spraying. These characteristics and escape mechanisms direct attention to possibilities of improving effectiveness by spraying two or three times in a single season.

Applications of 2-methoxy-3,6-dichlorobenzoic acid (dicamba) and 2,4-dichlorophenoxyacetic acid (2,4-D) controlled top growth the year of treatment, but western ironweed (Vernonia baldwini Torr.) recovered in the following year. One-half lb/A or more of 4-amino-3,5,6-trichloropicolinic acid (picloram) effectively controlled top growth and destroyed roots and rhizomes. Treatment with 2 lb/A of picloram resulted in ironweed-free plots by the fourth season after treatment.

Alfalfa (Medicago sativa L. ‘Vernal′) was seeded broadcast or in drill rows spaced 18 cm apart in the same operation that EPTC (S-ethyl dipropylcarbamothioate) was applied. For broadcast seeding, EPTC was applied as herbicide-treated crop seed, as granules mixed with crop seed, or as granules applied with the crop seed, but with the seed and granules carried in separate boxes on the seeder. For drill-row seeding, EPTC was applied between the rows in subsurface lines as a liquid or granular formulation; and within the rows as herbicide-treated seed, as granules mixed with the seed, or as granules carried in a box separate from the seed. Weed control and crop tolerance with the more effective simultaneous applications of EPTC were similar to those with conventional preplant-incorporated applications. To seed alfalfa (either broadcast or in drill rows) and apply EPTC in one operation, the methods wherein untreated seed and a granular formulation of EPTC were applied together but from separate boxes on the seeder were the most practical, because the mechanical components, the seed, and the formulated herbicide are all commercially available.

Dwarf spikerush [Eleocharis coloradoensis (Britt.) Gilly] is an aquatic plant that will displace waterweeds. It was studied to obtain information that will help to manage unwanted vegetation in natural aquatic situations. The morphology of seed and tubers was examined at the light- and scanning-electron microscope levels. Inflorescences were found to bear 3 to 12 florets that matured acropetally. The pericarp was made up largely of rows of annulated cells covered with a water-soluble, waxlike substance that leached away when stored in water at 4 to 6 C. The seed coat consisted of three layers. Each layer contained lipids, giving evidence that they were composed of cutin. When the seed germinated, the cotyledonary sheath emerged first, followed by the culms. Tubers formed and matured in about 30 days. The shoot apices of tubers each had two buds that were protected by five to seven overlapping membraneous leaf scales. When tubers sprouted the longest bud grew first. The second bud contained the culm meristem.

Weeds in row crops of the Lower Coastal Plain in Alabama were sampled by line transects in both April and August. More than 100,000 feet of transects were assayed, with detailed questioning of producers in the area. The most important weeds of summer and fall and of winter and spring are listed, with per cent coverage and per cent frequency for weeds of row crops.

The influence of calcium arsenate (48% w/w tricalcium arsenate) rate, physical form, time of application, and phosphorus (P) rate on the growth of annual bluegrass (Poa annua L.) and Bray P1 extractable arsenic (As) were investigated. Both powder and granular formulations reduced clipping yields and enhanced extractable As levels. Higher initial soil As activity and significantly better control were obtained in one study when the powder formulation was used. Similar levels of control were achieved whether the As was applied prior to germination or to the mature turf. Soil P-levels did not influence the effectiveness of either As formulation.

Canada thistle (Cirsium arvense L.) plants containing one elongated and one recently emerged shoot from the same root segment were treated with 14C-ring labeled atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine]. Fourteen days after atrazine application to the elongated shoot 98% of the recovered activity remained in this shoot. The distribution pattern of 14C suggested movement with the transpiration stream. Of the 14C in the treated shoot, 82% was in the form of unaltered atrazine at 14 days after application. Greenhouse studies with nonlabeled atrazine indicated that this herbicide had only an indirect effect on portions of the plant located basipetally to the area of application.

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.

The joint action of metribuzin and tridiphane was investigated in metribuzin-tolerant (T) and metribuzin-susceptible (S) soybean and tomato cultivars within species, respectively, under growth room studies. Maple Arrow (T) and Maple Amber (S) exhibited similar tolerance to tridiphane applied at soybean emergence. Vision (T) tomato was more sensitive to tridiphane than was Springset (S) tomato, the reverse of the relative tolerance to metribuzin. A phytotoxic interaction was demonstrated following application of tridiphane and metribuzin at the respective rates (kg ai ha−1) of 0.1 and 1.1 in Maple Arrow (T) soybeans, 0.05 and 0.25 in Maple Amber (S) soybeans, and 0.25 and 0.2 in Springset (S) tomato. Tridiphane applied 1 or 4 h before metribuzin caused the greatest phytotoxicity in Maple Amber (S) soybeans. Soybean field results generally supported those of growth-room studies. Foliar spray pretreatment with tridiphane increased total radioactivity in Springset (S), decreased the total root radioactivity and increased total shoot radioactivity in both Vision (T) and Springset (S) and decreased metabolism of metribuzin to water soluble conjugates in Springset (S) roots over 24 h following 14C-metribuzin application to roots of intact tomato seedlings. The increased uptake, translocation to the shoots, and decreased root metabolism of metribuzin in Springset when pretreated with tridiphane could explain the phytotoxic interaction (which was unexpected, based only on the glucose detoxification pathway of metribuzin in tomato).

Bentazon [3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] was evaluated for Canada thistle [Cirsium arvense (L.) Scop. # CIRAR] control and birdsfoot trefoil (Lotus corniculatus L. ‘Norcen’) tolerance. Bentazon applied in split applications controlled more Canada thistle than a single application of equal rate in both greenhouse and field studies. Bentazon applied four times reduced the level of total nonstructural carbohydrates (TNC) in the roots of both greenhouse- and field-grown Canada thistle and increased birdsfoot trefoil injury more than bentazon applied in a single application of equal rate. All bentazon treatments caused unacceptable injury when birdsfoot trefoil was grown for seed.

International challenges in any field of science occur only from time to time. On occasions where the development of mankind is seriously endangered due to constraints of one kind or another, the ground for the germination of such challenges may be particularly fertile.

Microscopic examination of central and soft offset bulbs of wild garlic (Allium vineale L.) at senescence of the parent plants in May and June revealed embryonic plants with numerous root primordia and four or five shoot primordia. Hardshell bulbs and aerial bulblets contained only one or two root primordia and three leaf primordia. The embryonic plants of central, soft offset, and hardshell bulbs elongated slowly during the after-ripening period. Rapid cell division, cell elongation, and initiation of new leaves took place after termination of the after-ripening period in all but the dormant hardshell bulbs. In November, new hardshell bulbs could be seen at the base of plants developed from central and soft offset bulbs.

Quackgrass (Agropyron repens (L.) Beauv.) was controlled with applications 1 to 8 months prior to plowing and planting of from 1 to 4 lb/A 2,3,5-trichloro-4-pyridinol (pyriclor). Corn (Zea mays L., hybrid W530) planted on pyriclor-treated plots grew normally and yielded as well as on plots given the standard preplow treatment of 2 lb/A of 2-chloro-4-ethylamino-6-isopropylamino-5-triazine (atrazine). Oats (Avena sativa L., var. Portage) was injured by soil residues of pyriclor from 2-lb/A applications made 20 months previously. Alfalfa (Medicago sativa L., var. Vernal) was somewhat more tolerant of pyriclor than was oats.

The possibility of using 2,4-D as a soil sterilant was investigated by Crafts in 1949. He concluded that 2,4-D may be useful under very dry conditions. In 1954, Shafer reported several years work using soil applications of 2,4-D for control of perennial weeds. Since that time many research workers have evaluated 2,4-D and other phenoxy herbicides for the control of bindweed and other perennial weeds. Results of these trials varied from excellent to poor.

During 1962, barnyardgrass (Echinochloa crusgalli (L.) Beauv.) seedlings were infested by the larvae of Hyperodes humilis Gyll. The larvae attacked the growing points and the youngest tissues in the crown as well as meristematic tissues of intercalary growth. These infestations produced considerable decreases of barnyardgrass growth and yields, suggesting the possibility of effective biological control of barnyardgrass.