Seed dormancy of common milkweed (Asclepias syriaca L.) is broken by a few days of moist low-temperature after-ripening. The duration of low-temperature after-ripening of the seeds is temperature dependent. Seedling emergence is best when the seeds are planted 1 to 2 cm deep and extremely limited when planted 6 cm deep. Seedlings have the capacity to produce new shoots if clipped in the 1 to 1¾-leaf pair stage and multiple shoots if clipped in the 2 to 2½-leaf pair stage. All seedlings reaching the 4 to 4½-leaf pair stage before clipping produced new shoots.

The herbicide S-ethyl hexahydro-1H-azepine-1-carbothioate [molinate] at 0, 3, and 6 lb/A was applied to drill-seeded rice [Oryza sativa L.] into the irrigation water at 8, 13, and 20 days after rice and weed emergence; the plots remained flooded for 2, 7, or 12 days. Three lb/A applied when weeds had 1 to 6 leaves and rice had 2 to 8 leaves controlled barnyardgrass [Echinochloa crusgalli (L.) Beauv.] and broadleaf signalgrass [Brachiaria platyphylla (Griseb.) Nash] and did not injure rice when the water remained for 7 or 12 days. Weed control and yield of rice were reduced when the irrigation water was held for only 2 days. When the weeds were tillering, molinate controlled barnyardgrass better than it controlled broadleaf signalgrass. Molinate at 0, 3, and 6 lb/A was applied to drill-seeded rice into the irrigation water 1 week after rice and weed emergence; 7 days later the water was either left on the plots or was drained for 5, 10, 20, or 29 days. Three lb/A usually prevented reinfestations of barnyardgrass when plots were drained for 5, 10, or 20 days. Barnyardgrass reinfested rice drained for 29 days and reduced yields.

Dicamba (3,6-dichloro-o-anisic acid), 1,1′-dimethyl-4,4′-dipyridinium ion (paraquat), and (2,4,5-trichlorophenoxy)-acetic acid (2,4,5-T) were applied as foliar sprays to 4-year-old sweetgum (Liquidambar styraciflua L.), green ash (Fraxinus pennsylvanica Marsh.), water oak (Quercus nigra L.), and loblolly pine (Pinus taeda L.). For the three hardwood species the amount of herbicide absorbed and translocated, as measured 4 days after application, was correlated closely with tops killed 1 year later. Applications in May were more effective than those made later in the growing season. Loblolly pine was defoliated by all herbicides but recovered the second season after spraying.

In experiments conducted at the International Rice Research Institute, Philippines, all commonly marketed formulations and derivatives of either [(4-chloro-o-tolyl)oxy]acetic acid (MCPA) or (2,4-dichlorophenoxy) acetic acid (2,4,D) performed in about the same way and were equally safe for use in controlling barnyardgrass [Echinochloa crusgalli (L.) Beauv.] and other annual weeds in transplanted rice (Oryza sativa L.). Eleven-day-old rice seedlings were more susceptible to amine salts of 2,4-D or MCPA than 21-day-old seedlings. Granular formulations of some chemicals were relatively less toxic than liquid formulations. The toxic effect of spraying the potassium salt of MCPA was less prolonged on the indica variety, IR22, than it was on the japonica variety, Chianung 242, which had delayed flowering and maturity.

Eight herbicide postemergence treatments were applied to proso millet (Panicum milaceum L.) at three growth stages. The dimethylamine salt of (2,4-dichlorophenoxy)acetic acid (2,4-D) at 0.56 kg/ha had significantly higher grain yields than the weedy check. All herbicides except the amine of 2,4-D at 0.28 kg/ha appeared to injure proso millet plants by varying degrees; however, yields were not greatly affected. All herbicides gave excellent control of redroot pigweed (Amaranthus retroflexus L.) when applied to proso millet in the 4 to 6-leaf stage. Weed control was poorer when spraying was delayed until proso millet was in pre-boot and post-flower stages.

Young vegetative clones of yellow nutsedge (Cyperus esculentus L.) were propagated by subdivision of older clones and then grown 6 months under photoperiods of 8 to 24 hr. Early stages of development of basal bulbs, tubers, and flowering structures were characterized in terms of apical meristem activity and differentiation of various foliar appendages: cladophylls, prophylls, leaf primordia, foliar tube development, and involucral leaves. Ramification of the axial stem system was interpreted as a repeating phylogenetic sequence: viz., undifferentiated axial meristem (from basal bulb) å primitive stem (rhizome) å advanced stem (new basal bulb). New photosynthetic leaves differentiated every 4.5 to 5 days, and each exhibited a sigmoid pattern of growth for 24 to 40 days. As photoperiods increased from 14 to 24 hr, certain active vegetative processes—total peripheral shoot development, rhizome proliferation, and rate of higher order shooting—were progressively promoted. The rate of differentiation of indeterminate rhizome tips into basal bulbs (new shoots) was maximum at 16 hr and into tubers at 8 to 12 hr. Delayed tuberization, however, occurred even at the longest photoperiod. Flowering occurred only at photoperiods of 12 and 14 hr. Active vegetative processes were competitive with tuberization, and flowering was competitive with both active and dormant vegetative development.

Postemergence treatments with 3-[p-(p-chlorophenoxy)phenyl]-1,1-dimethylurea [chloroxuron], for broadleaf weed control in soybeans [Glycine max (L.) Merr.] often partially defoliate, and temporarily stunt the crop. Chloroxuron was applied at 3 lb/A and at 1, 1½, and 3 lb/A with surfactant over the tops of weed-free soybeans in the cotyledon, unifoliate, and first trifoliolate stages of growth in 1967, 1968, and 1969. Relatively small but statistically significant yield reductions, particularly from treatments in the unifoliate stage, resulted in 1967. No significant yield reductions resulted in 1968 or 1969. These studies demonstrated the ability of soybeans to withstand initial injury from early postemergence treatments with chloroxuron without serious reductions in yield.

Alfalfa (Medicago sativa L.) was killed or severely injured by parasitism from dodder (Cuscuta campestris Yunck. and C. indecora Choisy) when seeded August 1 or earlier in soil containing dodder seed. Alfalfa seeded August 15 or September 2 escaped injury from dodder, and became well-established before winter. Isopropyl m-chlorocarbanilate (chlorpropham) applied at 6 lb/A the following April controlled dodder effectively and did not injure alfalfa. A preemergence application of dimethyl tetrachloroterephthalate (DCPA) at 10 lb/A, followed by sprinkler irrigation, controlled 98 to 100% of the dodder at each of six dates of seeding in each of 2 years. DCPA often injured alfalfa seedlings severely, but most of them recovered and grew satisfactorily.

Aquatic plants and physical-chemical data were collected during 1969 from 19 ponds and lakes. The fertility of these waters, as indicated by specific conductance, appeared to be a function of watershed area over the range 0 to 100 hectares. For watersheds greater than 100 hectares, differences in soil type and farming intensity were major causes of variability. Chara (Chara spp.) was found at specific conductances from 96 to 445 micromhos/sq cm (at 18 C) but was most abundant between 218 and 300. Chara also grew best in the upper half of the transparency range at Secchi disc readings varying from 2.4 to 5.8 m. Elodea (Elodea canadensis Michx.) flourished at specific conductances of 224 to 300 micromhos/sq cm and at transparencies from 2.7 to 5.8 m. Largeleaf pondweed (Potamogeton amplifolius Tuckerm.) was found only in the least fertile impoundment, whereas curlyleaf pondweed (P. crispus L.) occurred only in the most fertile impoundment. Sago pondweed (P. pectinatus L.) occurred at specific conductances of 200 to 349 micromhos/sq cm but was most prolific from 229 upward. This species also favored extensive shallow areas subject to a continuous summer flow.

Field experiments were conducted to study the effectiveness of 2,2-dichloropropionic acid (dalapon) for the control of 55 morphologically distinct ecotypes of johnsongrass (Sorghum halepense (L.) Pers.) collected throughout the United States and from several foreign countries. Ecotypes varied widely in their response to dalapon whether collected from Mississippi, from 10 other states, or from eight foreign countries. Initial control of seven ecotypes with dalapon increased 8 to 35% when nitrogen fertilization was increased from 0 to 300 lb/A. Regrowth of surviving plants was more vigorous with increased nitrogen levels so increased fertility reduced final control. Comparative differences in the susceptibility of the seven selected ecotypes to monosodium methanearsonate (MSMA) were not as great as those obtained with dalapon. Varying the rate of nitrogen fertilization had less effect on johnsongrass susceptibility to MSMA than to dalapon. Dalapon controlled sorghum almum (Sorghum almum Parodi) better than johnsongrass.

The influence of soil pH (4.3 to 7.5) on the phytotoxicity of herbicides incorporated into high organic soils was studied. Phytotoxicity increased as the soil pH increased and reached a maximum at pH 6.5 for the weak aromatic acids 3,6-dichloro-o-anisic acid (dicamba) and (2,4-dichlorophenoxy)-acetic acid (2,4-D) and the weak bases 2,4-bis(isopropylamino)-6-methoxy-s-triazine (prometone) and 3-amino-s-triazole (amitrole). Conversely, phytotoxicity increased as soil pH decreased and reached a maximum at pH 4.3 for the weak aliphatic acid 2,2-dichloropropionic acid (dalapon), the cationic herbicides 6,7-dihydrodipyrido[1,2-a:2′,1′-c]pyrazinediium ion (diquat) and 1,1′-dimethyl-4,4′-bipyridinium ion (paraquat), and a nonionic herbicide S-propyl dipropylthiocarbamate (vernolate). Soil pH levels between 4.3 and 7.5 had no effect on the phytotoxicity of (a) the weak aromatic acids 3-amino-2,5-dichlorobenzoic acid (chloramben) and 4-amino-3,5,6-trichloropicolinic acid (picloram); and (b) the nonionic herbicides 2,6-dichlorobenzonitrile (dichlobenil), 5-bromo-3-isopropyl-6-methyluracil (isocil), 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), and 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin). A change of one pH unit decreased the phytotoxicity of 2,4-D, dicamba, dalapon, prometone, amitrole, paraquat, and vernolate by a factor of two to four depending on the particular herbicide and the pH values considered.

Dicamba (3,6-dichloro-o-anisic acid) and 2,3,6-trichlorobenzoic acid (2,3,6-TBA) applied in lanolin pastes to leaves or roots of host plants growing in soil were translocated acropetally and affected witchweed (Striga lutea Lour.) plants parasitizing roots of host plants. Emerged witchweed plants exhibited characteristic epinastic responses while emergence of other witchweed plants was delayed. Broadcast foliar treatments of dicamba and 2,3,6-TBA to corn (Zea mays L.) applied before witchweed emergence generally reduced the intensity of the infestation and delayed emergence. However, injury to corn, expressed as failure of kernel development and grain yield decreases, sometimes occurred. Injury was greater when herbicide application was delayed until corn was in the early tassel stage. Dicamba was more effective than 2,3,6-TBA for witchweed control. However, no treatment gave season-long control of witchweed. Yearly variations in corn injury precluded a selection of optimum treatment dates and rates for control of witchweed by this technique.

A belt-carried small-plot sprayer for field research work was constructed. Spray materials are prepared in 1-quart polypropylene bottles, and these are placed directly in the pressure canister of the sprayer for application. The system is charged by a CO2 pressure source and the spray applied through conventional booms.

A time course study on the in vitro effect of 10–4 M (2,4-dichlorophenoxy)acetic acid (2,4-D) on the metabolism and incorporation of specific 14C-labeled glucose into pea (Pisum sativum L., var. Alaska) and corn (Zea mays L., var. Golden Cross) tissues showed a preferential release of C-1 as CO2 which was affected by 2,4-D. The glucuronic acid pathway was stimulated greatly in pea roots and slightly in corn stems; it was inhibited in corn roots. The pentose phosphate pathway was affected in an opposite pattern. The incorporation of both labeled carbon atoms into alcohol-insoluble residue was also affected by 2,4-D. The degree of effect, however, varied from pea to corn and from roots to stems. Analysis of the alcohol-soluble fraction revealed different effects of 2,4-D on labeling of some of the amino acids, an increase in fructose content, and an accumulation of malic acid.

Tolerance of Yuchi arrowleaf clover (Trifolium vesiculosum Savi) to preemergence application of dimethyl tetrachloroterephthalate (DCPA) and isopropyl m-chlorocarbanilate (chlorpropham) and preplant incorporation of N-butyl-N-ethyl-a,a,a-trifluoro-2,6-dinitro-p-toluidine (benefin), 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin), S-ethyl dipropylthiocarbamate (EPTC), and S-propyl dipropylthiocarbamate (vernolate) were evaluated over a 3-year period on two soils. DCPA did not injure Yuchi arrowleaf clover in any experiments over the 3-year period. Lower rates of benefin and chlorpropham caused either moderate or no injury depending upon the year and location. Yield reductions of Yuchi clover generally were greater on the Norfolk than on the Lucedale soil. Early injury, as reflected by the first forage harvest, was transitory in many instances.

Dichlobenil (2,6-dichlorobenzonitrile), 3-tert-butyl-5-chloro-6-methyluracil (terbacil), and 3-tert-butyl-5-bromo-6-methyluracil (hereinafter referred to as DP-733) were applied annually for 3 years as soil surface or incorporated treatments for weed control in young peach (Prunus persica (L.) Batsch., var. Redhaven) trees. Average monthly ratings showed significant increases in bermudagrass (Cynodon dactylon (L.) Pers.) control with incorporation of all three herbicides. Treetrunk diameters in incorporated dichlobenil plots were greater than those in surface-applied dichlobenil plots. Incorporation in the soil reduced loss of dichlobenil, terbacil, and DP-733. The herbicides did not accumulate in the 0 to 15-cm soil layer. Low concentrations were detected in the 30 to 60-cm soil depth 1 year after the third annual application of 6.72 kg/ha of dichlobenil and 4.48 kg/ha of DP-733. Terbacil was not present in detectable amounts at 30 to 60 cm but was present in the 15 to 30-cm layer of 4.48 kg/ha plots.

Rapid absorption and limited acropetal movement of 14C from p-nitrophenyl-α,α,α-trifluoro-2-nitro-p-tolyl ether (hereafter referred to as fluorodifen) labeled with 14C at either the 1 position of the p-nitrophenyl ring (fluorodifen-1′-14C) or the trifluoromethyl carbon (fluorodifen-14CF3) were observed in peanut (Arachis hypogaea L., var. Starr) seedlings after root treatment for 48 hr followed by 96 hr in nutrient solution. Major products of degradation of fluorodifen-1′-14C were p-nitrophenol and Unknown I (possibly a conjugate of p-nitrophenol). Some p-nitrophenyl-α,α,α-trifluoro-2-amino-p-tolyl ether and several minor unknowns were detected. The major product of degradation of fluorodifen-14CF3 was Unknown II (possibly a conjugate of 2-amino-4-trifluoromethylphenol). Some 2-amino-4-trifluoromethylphenol and traces of p-nitrophenyl-α,α,α-trifluoro-2-amino-p-tolyl ether, p-aminophenyl-α,α,α-trifluoro-2-nitro-p-tolyl ether, p-aminophenyl-α,α,α-trifluoro-2-amino-p-tolyl ether, and several minor unknowns also were detected. A major pathway of fluorodifen degradation in peanut seedlings is postulated whereby fluorodifen is reduced to the 2-amino derivative which is cleaved at the ether linkage to yield p-nitrophenol and 2-amino-4-trifluoromethylphenol. The respective phenols are then conjugated with natural plant substances to form water soluble conjugates.

Trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), IAA (indoleacetic acid), kinetin (6-furfurylamino purine), and their combinations in culture solutions did not affect cotton (Gossypium hirsutum L., var. Deltapine Smooth Leaf) germination but reduced primary root and shoot lengths of seedlings. Trifluralin alone and in combination with IAA or kinetin inhibited lateral root development. When IAA and kinetin were both applied with 5 ppmw trifluralin, lateral roots developed.

The influence of pH, temperature, ionic strength, and protein modification on the sorption (moles of chemical bound per mole of protein) of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) and 3′,4′-dichloropropionanilide (propanil) to bovine serum albumin (hereinafter referred to as BSA) was examined. Free amino groups of BSA were involved in the binding of both diuron and propanil. In addition, tryptophanyl residues appeared to be involved in the binding of propanil. Studies made with derivatives of diuron suggested that the amide hydrogen and carbonyl oxygen of the phenylamide are involved in the binding mechanism. Conformation of the protein was suggested to control the extent of binding. Increased chlorination of the phenyl ring was correlated with increased binding onto BSA. Propanil was bound to a greater extent than diuron by the protein.

The effect of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) and isopropyl m-chlorocarbanilate (chlorpropham) on in vivo levels of ATP in Chlorella sorokiniana Shihira and Krauss were compared. Diuron inhibited the photochemical, but not the oxidative, production of ATP, whereas chlorpropham inhibited both systems. Diuron equally inhibited growth and ATP synthesis, but chlorpropham had a stronger effect on ATP level than on growth.