Common milkweed (Asclepias syriaca L.) seed did not survive storage in water for 1, 2, and 12 months at 40, 30, and 5 C, respectively; but under dry storage seed viability was destroyed only at 40 C for 5 months. Stratifying common milkweed seed in water at 5 C was more effective in breaking dormancy than at 22 C. Mechanical scarification also caused a significant increase in germination. Exogenous 6-furfurylamino purine (kinetin) and gibberellic acid-3 (GA) increased germination while indole-3-acetic acid (IAA) had no effect. The optimum germination temperature scheme for common milkweed was an alternating 20 to 30 C, the maximum between 35 and 40 C, and the minimum between 15 and 20 C. Common milkweed seedlings were more susceptible to moisture stress than kochia [Kochia scoparia (L.) Schrad.] but less susceptible than hemp dogbane (Apocynum cannabinum L.) and sunflower (Helianthus annuus L.). In a greenhouse study common milkweed was less drought tolerant than eight other weed species. Common milkweed seedlings tolerated wider pH ranges than honeyvine milkweed [Ampelamus albidus (Nutt.) Britt.], kochia, and sunflower. Common milkweed seedlings were less tolerant to salt solutions than four other species. Common milkweed emerged from 6-cm depths in Sharpsburg silty clay loam (sicl) at 20 or 30 C but only from the 3-cm depth at an alternating 20 to 30 C. Results from root box studies showed that common and honeyvine milkweed produced less shoot and root weight than kochia and sunflower and had a lower growth rate index of roots than sunflower. Common milkweed seedlings resprouted 21 days after planting when clipped at ground level. As days from planting to clipping increased, sprouting activity increased.

The absorption by bean (Phaseolus vulgaris L. ‘Black Valentine’) of 2,4-bis-(isopropylamino)-6-(methylthio)-s-triazine (prometryne) at 1 μM concentration was increased in the presence of 10, 1, or 0.1 μM O,O-diethyl S-(ethylthio) methyl phosphorodithioate (phorate). An increase in absorption of 10 μM prometryne with addition of 1 μM phorate was recorded after 72 hr, but no increase was seen after 96 hr of absorption. Both prometryne and phorate inhibited state 3 respiration of mitochondria isolated from 6-day-old bean hypocotyls. Inhibition increased with increasing pesticide concentrations. When the pesticides were applied simultaneously, no interactions affecting state 3 respiration were observed. Neither prometryne nor phorate alone significantly affected phosphate accumulation by bean shoot mitochondria.

Greenhouse grown honey mesquite (Prosopis juliflora (Swartz) D.C. var. glandulosa (Torr.) Cockerell), huisache (Acacia farnesiana (L.) Willd.), and whitebrush (Aloysia lycioides Cham.) and field grown honey mesquite, huisache, whitebrush, live oak (Quercus virginiana Mill.), Arizona ash (Fraxinus velutina Torr.), and winged elm (Ulmus alata Michx.) were defoliated at several intervals following spray treatments with 4-amino-3,5,6-trichloropicolinic acid (picloram), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), or [(4-chioro-o-tolyl)oxy]acetic acid (MCPA). The time required by leaves to be retained on the plant after spraying to give maximum canopy reduction or death of plants varied among species. In most species, however, herbicide absorption and transport were complete within a 4-day period or less as compared to undefoliated treated plants.

The herbicide 3-amino-2,5-dichlorobenzoic acid (chloramben) was applied preemergence to soybeans [Glycine max (L.) Merr.] in 1969, 1970, and 1971. Herbicide band widths were 18, 36, and 53 cm, and there was a broadcast treatment. Cultivation and rotary hoeing were also imposed on the herbicide band widths as variables. A 36-cm band of chloramben was the minimum band width used which consistently maintained soybean yield when supplemented with mechanical tillage. Broadcast treated soybeans without mechanical tillage yielded as well as handweeded soybeans in 2 of 3 years. Each 4 kg/ha of weed growth reduced soybean yield 1 kg/ha. Average weed yield reduction due to cultivation was 100, 76, and 54% in 1969, 1970, and 1971, respectively, when average weed yields were 360, 1650, and 4720 kg/ha in successive years. Rotary hoeing reduced weed growth 48% and increased soybean yield 20% in 1970 but did not significantly affect weed or soybean yields in 1969 and 1971.

Upon germination, one or more rhizomes grew from the apical end of each yellow nutsedge (Cyperus esculentus L.) tuber. Each rhizome developed a basal bulb upon exposure to light. No significant differences in germination percentages existed between four lots of tubers which differed about fivefold in weight. The weight of plant material produced correlated significantly with the fresh weight of the tuber from which it emanated. When tubers germinated three successive times, over 60% of the tuber dry weight, carbohydrate, oil, starch, and protein were consumed during the first germination; but less than 10% of these constituents were uitlized during each of the next two germinations. Plants weighed significantly more after 43 and 91 days of growth with tubers attached throughout the period than when tubers were detached after emergence.

The competitive effects of sicklepod (Cassia obtusifolia L.) on soybeans (Glycine max L. ‘Bragg’) were studied on Malbis sandy loam soil and Chesterfield sandy loam soil during 1968 to 1970. Weed density was a linear function of soybean yield for the densities studied (0 to 15 weeds/m2). The regression coefficient of weed density (weeds per square meter) on bean yield (kilograms per hectare) was −92 and −101 for the two soils, respectively. When the data were combined across both soils and years, the regression coefficient was −95. Densities of 7.7 weeds/m2 reduced soybean yield 19 to 32% and 34 to 35% on the two soils, respectively. The weight of weeds at harvest was also inversely correlated to soybean yield. Sicklepod was more competitive when grown 15 to 30 cm from the drill than in the drill. Soybean yields were reduced in some instances when sicklepod was allowed to compete for as little as 4 weeks. If weeds were removed at 2 to 4 weeks after soybean emergence, no further weed removal was needed for maximum yield of soybeans.

Shade cages admitting three quantities of sunlight were placed in a dense field infestation of Canada thistle (Cirsium arvense (L.) Scop.), and the thistles were sprayed with (2,4-dichlorophenoxy)acetic acid (2,4-D) and with 2,4-D plus glucose in 1968 and again in 1969. Necrosis was greatest under full sunlight and when glucose was added. Regrowth the years after spraying increased with decreasing daylight intensities, but it was not significantly influenced by the addition of glucose. Percentage of necrosis in the year of treatment was not correlated with the percentage of regrowth the following year.

Achenes of Scotch thistle (Onopordum acanthium L.) contain a water-soluble germination inhibitor and are sensitive to differences in light quality. Germination of these achenes can be enhanced by the addition of 0.14 mmole of gibberellic acid and 1.0 mmole of potassium nitrate to the substrate. Dissected embryos exhibit germination responses similar to those observed for achenes. Naturally-distributed achenes recovered from the soil in the field increased in germination under fluorescent light and after washing. Achenes will not germinate on the surface of a constant-moisture-supplying substrate when exposed to an unsaturated atmosphere. The physical environment of the seedbed apparently is paramount in controlling germination and persistence of achenes of Scotch thistle.

The total quantity and concentration of six herbicides, isopropyl m-chlorocarbanilate (chlorpropham), 2-chloro-4-(ethylamino)-6-(isopropylamino-s-triazine (atrazine), 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron), 2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide (alachlor), 3-amino-2,5-dichlorobenzoic acid (chloramben), and (2,4-dichlorophenoxy)acetic acid (2,4-D), in unaerated, aqueous solutions absorbed by seeds of 11 soybean (Glycine max (L.) Merr.) strains were measured. Mechanism of movement of the herbicides from the aqueous solutions to the seeds in the experimental procedure employed was diffusion. Total quantity and concentration of herbicide found in the seeds differed significantly for both herbicides and soybean strains. Total quantity of herbicide absorbed was determined by total oil and percent oil of the seeds. The capacity of the seeds to absorb a given herbicide was more closely related to percent oil of the seeds than to total oil of the seeds. The emergence and seedling shoot weight of ‘Cutler’ soybeans were not affected appreciably by concentrations of linuron, atrazine, and chloramben (potassium salt) but were reduced by high concentrations of chlorpropham and alachlor and relatively low concentrations of 2,4-D (potassium salt) in the seeds.

Two herbicides, the alkanolamine salts of 2-sec-butyl-4,6-dinitrophenol (dinoseb) and 3-[p-(p-chlorophenoxy) phenyl]-1,1-dimethylurea (chloroxuron), were compared for their effects on soybean [Glycine max (L.) Merr., ‘Lee’] when applied topically. In initial studies, chloroxuron was damaging when applied twice to soybean and reduced yields in one of the two year's studies. In a third year's work, direct comparisons of topical applications of dinoseb and chloroxuron showed that soybean injury increased with increased rate of material at each soybean growth stage with the most severe initial damage in the two-trifoliate stage. Recovery was rapid with few significant yield decreases occurring. Chloroxuron was more effective in controlling the broadleaf weeds present. Both herbicides were most effective when weeds were in the seedling stage of growth.

A ‘penncross' bentgrass (Agrostis palustris Huds.) golf-type green was treated in the spring with seven herbicides at three rates each for three consecutive annual applications to assess their phytotoxicity. Herbicides which caused slight foliage injury the first year were tri-calcium arsenate, dimethyl tetrachloroterephthalate (DCPA), and polychlorodicyclopentadiene isomers (bandane); moderate injury occurred with 2,6-di-tert-butyl-p-tolyl methylcarbamate (terbutol) and N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine (benefin). No injury was observed with O,O-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl)benzenesulfonamide (bensulide) and 1-(2-methylcyclohexyl)-3-phenylurea (siduron). For the second and third year bandane was reapplied at half and tri-calcium arsenate at one fourth the original rate. Loss of bentgrass sod the second year was slight with terbutol and bandane and moderate with benefin and DCPA. No sod loss occurred with tri-calcium arsenate, siduron, and bensulide. Sod loss the third year was slight with tri-calcium arsenate, moderate with siduron and DCPA, and severe with bensulide, benefin, bandane, and terbutol. A persisting sod loss the fourth season, an observation year, was nil with tri-calcium arsenate; slight with siduron, benefin, and DCPA; slight to moderate with bensulide; moderate with bandane; and severe with terbutol.

The uptake of 14C-labeled butoxyethanol ester of (2,4-dichlorophenoxy)acetic acid (BEE of 2,4-D) from water by three species of fed and fasted fish was studied. Fish were exposed to either 0.3 or 1.0 mg/L of herbicide for up to 168 hr. Combined residues of the 2,4-D ester and its metabolic products were determined radiometrically in eight tissues and organs. Extracts of these organs were examined by thin layer chromatography and autoradiography. Maximum residue concentrations were observed in most organs of fed fish within 1 to 2 hr of exposure, and within 1 to 8 hr of exposure for fasted fish. After maximum residue concentrations were reached, the herbicide and/or its metabolites were eliminated rapidly.

The use of herbivorous fish for the biological control of aquatic weeds has great potential. The susceptibility of most herbivorous fish to low temperature is the principal factor limiting their use in the United States. The white amur (Ctenopharyngodon idella Val.) can tolerate low temperature and other water quality extremes. This fish has a voracious appetite for many aquatic plants, and after attaining a length of 30 mm, it is almost exclusively phytophagous. Factors affecting the feeding habits of the white amur include the species of plants and water temperature. The white amur has been introduced for aquatic weed control in various countries. This fish might ameliorate some of the aquatic weed problems in the United States, and also provide a new source of protein.

Growth of tops and rhizomes of established johnsongrass (Sorghum halepense (L.) Pers.) stopped almost completely in the cool winter season. Rhizome growth started in spring later than topgrowth. Rhizomes constituted more than 90% of the total subterranean weight. In a sward of pure johnsongrass, 60%, 30%, and 10% of the total subterranean weight were found in the 0 to 15-cm, 15 to 30-cm, and 30 to 45-cm soil layer, respectively. Water-soluble sugar content in rhizomes was high in early winter and in early summer and low in early spring and in fall. Less water-soluble sugars were found in shallow than in deeper rhizomes. In winter the sugars accumulated mainly in the deepest rhizomes. No clear relation was detected between the sprouting percentage of rhizome buds and growth, sugar content, or seasonal climatic factors. No case of complete sprouting inhibition was recorded during the year.

Persistence and movement of 4-amino-3,5,6-trichloropicolinic acid (picloram) were studied in silty clay loam soils located at Hays and Newton, Kansas. At Hays, picloram was applied to a Harney silty clay loam at rates of 2.24 and 3.36 kg/ha in 1963, 1964, 1965, 1966, and 1968 and at Newton to a Goessel (tentative) silty clay loam at rates of 1.12, 2.24, and 3.36 kg/ha in 1966. Fifteen, 20, or 30-cm increments of soil were taken from as deep at 2.4 m below the soil surface and bio-assayed with soybeans (Glycine max (L.) Merr. ‘Clark 63′) in 1968 and 1969. In both soils the highest concentration of phytotoxic residue remained near the soil surface, but differences between the two sites were evident. In the Goessel soil phytotoxic residues were detected only near the surface. In the Harney soil movement was uneven, but residues were detected as deep as 2.4 m below the surface. Soil cracks probably contributed to penetration of small amounts of the herbicide to as much as 2.4 m below the surface. Total picloram remaining in both soils diminished with time.