Freshly harvested seeds of Florida pusley (Richardia scabra L.) require light for germination. Gibberellic acid (GA3) successfully replaced the light requirement of both scarified and unscarified seeds, while cyclic 3′,5′-adenosine monophosphate (C-AMP) stimulated the dark germination of scarified seeds only. Cold-stratification reduced seed germinability. The germination inhibition by cold-stratification was reversed by both GA3 and KNO3 treatments. Indole-3-acetic acid (IAA), kinetin, thiourea, and acetylcholine (ACh), either had no effect or reduced the germination percentages of Florida pusley seeds under all conditions studied.

Over a 3-yr period the placement of weeds in relation to cotton (Gossypium hirsutum L.) plants greatly influenced the seed cotton yields. After 3-yr of competition the cotton with no weeds yielded about 2300 kg/ha. With weeds confined to between-the-rows placement, yields were about 850 kg/ha. When weeds were confined to in-the-row placement, the cotton was completely shaded and produced no yield. After 3-yr of intense competition throughout each entire growing season no statistical differences were demonstrated between the competitiveness of large crabgrass [Digitaria sanguinalis (L.) Scop.], spurred anoda [Anoda cristata (L.) Schlecht.], prickly sida (Sida spinosa L.) and velvetleaf (Abutilon theophrasti Medic.) to cotton.

Field experiments were conducted to compare the effects of 0.07, 0.14, 0.28, and 0.56 kg/ha of 2,4-D [(2,4-dichlorophenoxy)acetic acid] amine on plant growth, seed production, and seed quality when applied at four growth stages of summer rape (Brassica napus L. ‘Zephyr’) and turnip rape (Brassica campestris L. ‘Span’). At all growth stages, seed yield of turnip rape, was significantly reduced by each additional increment of 2,4-D. The difference in response of the two species may relate in part to differences in spray droplet retention of the leaf surfaces. The herbicide did not affect the germination of harvested seed although treatment with the higher rates at the bolting and flowering stages resulted in the production of some shrivelled seed that was lost on cleaning. Some herbicide treatments caused a marked increase in size of harvested seed. There was a trend towards decreased seed oil content with increasing rate of 2,4-D at the bolting and flowering stages, but oil production losses were mainly reflected through losses in seed yield. The time required for both species to reach maturity increased with increasing rate of herbicide when applied at the vegetative stages. In additional field studies, 2,4-D significantly reduced seed yield in turnip rape when applied at the 3- to 4-leaf stage at 0.035 kg/ha, and 0.018 kg/ha sometimes produced visible effects without noticeable loss in yield.

Low pressure and reduced pressure fan and reduced pressure hollow cone nozzles were compared to conventional fan and hollow cone nozzles to determine their potential for reducing spray drift. Other comparisons included two different spray pressures for a low pressure fan nozzle, low and reduced pressure fan nozzles versus air-aspirating foam nozzles, low pressure versus reduced pressure fan nozzles, and reduced pressure hollow cone nozzles versus reduced pressure fan nozzles. Spray recoveries within 36 m downwind of the spray release point were significantly greater for the low pressure and reduced pressure fan and reduced pressure hollow cone nozzles than for the conventional fan and hollow cone nozzles. An air-aspirating nozzle producing spray without foaming adjuvant resulted in significantly greater spray recovery than a low pressure fan nozzle. The recovery from a reduced pressure fan nozzle having a rated flow of 12.6 cm3/s was significantly greater than that from a low pressure fan nozzle.

Anatomical studies determined the effect of 0.8, 1.7, and 3.4 kg/ha of penoxalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine]; AC-92390 (N-sec-butyl-3-4-dimethyl-2,6-dinitrobenzenamine); oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide); and trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) on the cell structure of snap bean (Phaseolus vulgaris L. ‘Tenderette’) and soybean [Glycine max (L.) Merr. ‘Corsoy’]. Cellular abnormalities in the swollen and brittle area of the stem of treated plants included thinnerwalled cells, elongated xylem elements, hypertrophy and hyperplasia of cells, and anomalous rings of vascular tissue in the cortical region. Injury caused by the four herbicides was similar in snap bean and soybean.

Translocation of the 14C-labeled methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] was determined in cotton (Gossypium hirsutum L. ‘DPL 16′) from preemergence treatments and applications to leaves and stems in the field. Significantly greater methazole concentrations occurred in cotton from treatments to stems of 18 to 22-cm tall cotton than to leaves of 10 to 12-cm tall cotton or when applied preemergence. The radiolabel translocated primarily into the mature stems and leaves with lesser amounts translocating into the roots. Little 14C moved into the young growing points or into the seed and fiber of mature cotton. The distribution pattern of the 14C-label is characteristic of compounds which move primarily in the apoplast.

For prompt germination, the achenes of the nodding beggarticks (Bidens cernua L.) required 6 to 12 weeks of afterripening at 2 C and exposure to light. Without cold afterripening, a slow but complete germination was obtained after 2 weeks when the achene and seed inside, or the seed excised from the achene, were clipped at the distal end and germinated in light at 24 C. The embryo behaved like a clipped seed. Complete germination within 7 days, in light or dark, of the clipped seed was obtained by treating with gibberellic acid (GA) or N-6-benzyladenine (BA). The barriers to germination in the non-after-ripened seed appear to be first in the achene, the coverings of the seed itself and in a metabolic factor.

Foliar penetration of 14 C-difenzoquat (1,2-dimethyl-3,5-diphenyl-1-H-pyrazolium), in the presence of a surfactant, into both wild oat (Avena fatua L.) and barley (Hordeum vulgare L. ‘Conquest’), was rapid and continued at a nearly constant rate for 72 hr, the maximum time period studied; 93 and 84% of the applied dose was absorbed by the leaves of wild oat and barley, respectively. Added surfactants at 0.01% to 0.3% and high relative. humidity (RH) greatly enhanced the penetration of the herbicide into wild oat. An increase in temperature from 10 to 30 C resulted in a large increase in penetration. Commercial formulations of bromoxynil (3,5-dibromo-4-hydroxy-benzonitrile) + MCPA {[(4-chloro-O-tolyl)oxy] acetic acid} (1:1, w/w), 2,4-D[(2,4-dichlorophenoxy)acetic acid] ester and barban (4-chloro-2-butynyl m-chlorocarbanilate) markedly increased the penetration of 14C-difenzoquat into wild oat. Amine formulation of 2,4-D, on the other hand, had no effect on penetration. Foliarly-applied 14 C-difenzoquat rapidly translocated mainly in the acropetal direction. Most of the absorbed 14C, however, was accumulated in the treated area and a few centimeters above the treated area. There was some basipetal movement, and 24 hr after treatment 14C was detectable in the roots. Root uptake of 14C-difenzoquat was very rapid, but upward movement of 14C was slight, and even 24 hr after treatment most of it was retained by the roots. Chromatographic analysis of plant extracts up to 15 days after treatment with 14C-difenzoquat revealed no evidence of difenzoquat metabolism by wild oat, barley, and wheat (Triticum vulgare L. ‘Thatcher’). The selective action of difenzoquat in wild oat and barley cannot be accounted for by differences in its foliar penetration, translocation, or metabolism in these species.

The effectiveness of several preemergence and postemergence weed control systems for control of common cocklebur (Xanthium pensylvanicum Wallr.) in soybeans [Glycine max (L.) Merr.] was determined in field research over a 3-yr period. Sequential applications of metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one] at 1.1 kg/ha applied preemergence, and dinoseb (2-sec-butyl-4,6-dinitrophenol) at 1.7 kg/ha, 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] at 0.2 kg/ha, or bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-(4)3H-one 2,2-dioxide] at 1.1 kg/ha applied postemergence, provided at least 90% control of common cocklebur and increased soybean yields. Use of single herbicide applications was less effective than sequential applications, but metribuzin applied preemergence was more effective in controlling common cocklebur and increasing soybean yields than single applications of any herbicide applied postemergence. Effective control of common cocklebur with sequential herbicide treatments increased soybean seed grades by reducing discounts caused by several grade lowering components including moisture content and foreign material in harvested seed. Use of all herbicide practices increased returns above specified costs, but greatest returns followed use of sequential treatments.

Effectiveness of bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-(4)3H-one 2,2-dioxide] for control of common cocklebur (Xanthium pensylvanicum Wallr.) in soybeans [Glycine max (L.) Merr.] was evaluated in field research over a 3-yr period. Bentazon, applied over-the-top at 0.6 to 1.1 kg/ha, controlled common cocklebur more effectively than over-the-top or directed applications of dinoseb (2-sec-butyl-4,6-dinitrophenol) at 0.8 to 1.7 kg/ha or 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] at 0.2 kg/ha. Single applications of bentazon were highly effective for control of common cocklebur, but multiple applications usually provided the best control and highest soybean yields. A preemergence treatment of metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one] at 1.1 kg/ha and a postemergence application of bentazon at 1.1 kg/ha provided 92 to 99% control of common cocklebur. Control of common cocklebur with bentazon reduced discounts in harvested soybean seed caused by excessive moisture content and foreign material. The reduction in discounts improved soybean seed grades.

The effects of common cocklebur (Xanthium pensylvanicum Wallr.) on soybean [Glycine max (L.) Merr.] yields, grades, and net returns were determined by regression analysis of data from 450 research plots from 1971 through 1973. Common cocklebur control from 0 to 100% was achieved by various combinations of preemergence and postemergence practices. Foreign matter in soybean seed samples was 0.7% with total common cocklebur control and 5.1% with no control. At least 70% control of common cocklebur was required to avoid deductions from gross harvested weights due to seed moisture levels exceeding 13%. Small discounts for damaged kernels occurred when common cocklebur control was less than 40%. With 100% common cocklebur control, the estimated US soybean grade was 1.3. Failure to control common cocklebur resulted in a predicted grade of 3.9. When adjusted for various weight discounts, soybean yields were 1170 kg/ha without control of common cocklebur and 1890 kg/ha for 100% control. Soybean yields were increased about 6% for each 10% increase in common cocklebur control. Net returns to land, management, and general farm overhead were $63/ha when common cocklebur was not controlled, and $119/ha with 95% control.

Soil-incorporated treatments of dichlobenil (2,6-dichlorobenzonitrile) at 4.5 or 9 kg/ha completely controlled field horsetail (Equisetum arvense L.) for 2 yr and at 9 kg/ha, control was 90 to 99% in the third year. Mulching with sawdust after surface application of dichlobenil gave similar results. In an area treated at 9 kg/ha and isolated from emerged field horsetail, there was no reappearance of field horsetail until 5.5 yr after treatment. Japanese holly (Ilex crenata Thunb.) and azalea (Rhododendron X ‘Rosebud’) planted a year after treatment made as much growth in treated as in adjacent untreated soil. Douglas fir seedlings [Pseudotsuga menziesii (Mirb.) Franco] made as much growth in treated as in untreated soil only when planted 2 yr after treatment. Strawberry (Fragaria X ‘Northwest’) plants made approximately 80% as much top growth in treated as in untreated soil when planted 2 yr after herbicide application.

A mixture of diquat [6,7-dihydrodipyrido(1,2-α: 2′,1′-c) pyrazinediium ion] and copper sulfate pentahydrate was applied to artificial chinook salmon (Onchorhynchus tshawytscha Wal.) spawning channels to reduce excessive growths of algae [Cladophora glomerata (L.) Kutz]. Juvenile salmon were not harmed by the applications. A concentration of 100 ppb w/w diquat plus 150 ppb copper-ion was maintained for 3 hr. The alga was controlled satisfactorily for distances up to 0.5 km per treatment. Each treatment consisted of one to three applications, each made on consecutive days. Water temperature was 11.2 C during three winter applications and 15.5 C during a spring application. Diquat was rapidly sorbed out of the treated water to 3.8 ppb at 1.6 km. Copper-ion residues dissipated to 60 ppb at 1.6 km.

When planted with narrow (53 cm) row spacing, cotton (Gossypium hirsutum L.) ‘McNair 210’ produced maximum yields with as little as 6 weeks of weed-free maintenance. With wider row spacing (79 and 106 cm), however, 10 and 14 weeks of weed-free maintenance were required for maximum yield. When weeds were allowed to grow in cotton for more than 2 to 4 weeks after planting, yield reductions occurred. This tolerance period did not differ with row widths of 53, 79, or 106 cm.

The seed weevil (Microlarinus lareynii Jacquelin duVal) and the stem weevil (M. lypriformis Wollaston) were introduced into the United States and the West Indies to control puncturevine (Tribulus terrestris L.) and Jamaica feverplant (T. cistoides L.). In 14 yr these weevils have partially controlled these weeds in most areas where weevil establishment has occurred. However, indigenous parasitoids, predators, and cold weather affect weevil densities. Presently a coldhardy strain of seed and stem weevils has become established in Nevada and promise control in colder areas.

A technique of collecting contiguous soil samples was developed that showed the distribution of nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline] in the soil profile. About 60 days after the herbicide was applied and incorporated with a disk harrow, the soil was sampled from two sites in 1968, five sites in 1969, and five sites in 1970. Bioassays, that utilized root lengths of grain sorghum [Sorghum bicolor (L.) Moench ‘Dekalb 57E’], indicated large variation in herbicide concentrations among adjacent or on contiguous soil samples.

Six herbicides were applied monthly from February to May for control of large crabgrass [Digitaria sanguinalis (L.) Scop.] and goosegrass [Eleusine indica (L.) Gaertn.]. Bensulide [O,O-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl)benzenesulfonamide] applied in February or March controlled at least 70% of large crabgrass, whereas, treatments applied in April resulted in similar control at two of three locations. All herbicides failed to control large crabgrass when applied in May. Oxadiazon [2-tert-butyl-4(2,4-dichloro-5-isopropoxyphenyl)-δ2-1,3,4-oxadiazolin-5-one] and butralin [4-(1,1-dimethylethyl)-N-(1-methylpropyl)-2,6-dinitrobenzenamide] controlled goosegrass for the full season when applied in March or April. Oxadiazon also controlled goosegrass when applied in May.

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.

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.