The differential tolerance of prickly sida (Sida spinosa L.) and cotton (Gossypium hirsutum L.) to methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione]was studied under greenhouse conditions. Methazole at dosages up to 8.96 kg/ha did not affect emergence of either species. Applications via nutrient solution, as well as preemergence and postemergence (over-the-top) treatments were phytotoxic to both species, becoming more pronounced with increasing concentration and time. However, a margin of selectivity between species occurred at dosages from 0.56 to 3.36 kg/ha preemergence. Directed sprays of methazole were not injurious to cotton. Selectivity would be influenced by plant size and method of application as well as biochemical differences between species.

An applicator is described that uses the principle of the cone seeder to obtain uniform distribution of granules along the length of the plot and conventional, commercially manufactured, granular spreaders for distribution across the width of the treated area. If plot size is held constant, no calibration or adjustment is necessary when rates of application are varied or when different formulations of granules are used.

The degree and rate of volatilization, and the partial vapor pressures of the methyl, n butyl, and n octyl esters of 2,4-D [(2,4-dichlorophenoxy)acetic acid] were determined at ambient temperatures using a kinetic system approximating field-air conditions. The initial surface area/applied mass ratio (Q), as well as temperature and the type of compound, determined the volatility. Only when the Q values were kept constant did the volatility decrease with increasing chain length and decreasing saturated vapor pressure as expected. A mathematical model was constructed. Similar results were obtained for the amine salts which had saturated vapor pressures of ca 10−10 mm Hg at 38 C. Vapor drift can be essentially eliminated by use of the amine salts.

Common purslane (Portulaca oleracea L.) seeds, produced by the same plants, had different degrees of dormancy. The dormancy variations were caused neither by low seed viability nor by location on the plant where seeds were produced. Seed water content and seed age at time of collection contributed to, but were not solely responsible for, the dormancy variations. Immature, brown seeds of high water content were less dormant than the more mature, black seeds of low water content. The immature seeds germinated better in the dark than did the more mature seeds. A puncture in the seed, over the radicle, broke purslane dormancy. Dormancy was not caused by blockage of water imbibition by seeds. Purslane dormancy developed during later stages of seed maturation on the mother plant.

In field studies, surfactant and phytobland oil were compared as additives to herbicides and herbicide combinations for postemergence weed control in cotton (Gossypium hirsutum L. ‘Stoneville 7A’). Addition of phytobland oil to MSMA (monosodium methanearsonate) and MSMA + fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea], dinoseb (2-sec-butyl-4,6-dinitrophenol), or norea [3-(hexadydro-4,7-methanoindan-5-yl)-1,1-dimethyl-urea] had no significant effect on weed control when applied as directed treatments to weeds in cotton 7 to 15 cm tall. In cotton 15 to 23 cm tall, addition of phytobland oil to MSMA + linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] and MSMA + linuron + prometryne [2,4-bis(isopropylamino)-6-(methylthio)-s-triazine] increased weed control when compared to the same treatments with surfactant. MSMA + linuron + phytobland oil decreased cotton yields. Addition of phytobland oil to DSMA (disodium methanearsonate) and DSMA combinations had no effect on weed control when compared to the same treatments with surfactant. There were no differences in several paraffinic phytobland oils or surfactant when used as additives to MSMA + fluometuron for weed control in cotton 7 to 15 cm tall.

Rhinocyllus conicus Froel. (Col.: Curculionidae) larvae feeding within the capitula of Carduus thistles may reduce production of viable seeds. Each R. conicus larva destroyed 9.7 developing musk thistle (Carduus nutans L.) seeds. An average musk thistle capitulum, 29.2 mm diameter, produced 15.3 viable achenes per millimeter of diameter for an average of 447 viable seeds. Surveys of 23 release sites in Virginia revealed that thistles at 12 had sustained a population of weevils. Weevil eggs at six sites have increased in abundance, and establishment appears assured. Colonization of R. conicus was enhanced by spring or early summer releases; larger stocks of insects were required for late summer releases. The weevils exhibited better synchronization with musk thistle than with plumeless thistle (Carduus acanthoides L.); and best success has been achieved where extensive, persistent stands of musk thistle were available.

Unmodified, cyanoethylated, and crosslinked corn starches were reacted with 2,4-dichlorophenoxyacetyl chloride in pyridine to produce the corresponding 2,4-D [(2,4-dichlorophenoxy)acetic acid]esters of high acyl content. Hydrolysis studies at pH 6 and 8 at ambient temperature showed that these insoluble compositions liberated varying amounts of 2,4-D and soluble 2,4-D esters by ester link and glucoside bond cleavage, respectively, at rates that indicate their possible use as controlled-release herbicides.

Two methods of controlling weeds during the establishment of crownvetch (Coronilla varia L. ‘Chemung’) were studied. The first involved broadcast-incorporated spray treatments with either EPTC (S-ethyl dipropylthiocarbamate) or benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine) before planting. At planting, simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] or bromacil (5-bromo-3-sec-butyl-6-methyluracil) was applied in bands between seeded rows of crownvetch. Excellent weed control and good crownvetch establishment were obtained consistently, but in some years bromacil damaged seedling crownvetch excessively. In the second, weed control and subsequent crownvetch establishment were successful for 4 consecutive years after broadcastpreplanting treatments of EPTC or benefin, followed by a postemergence spraying with dinoseb (2-sec-butyl-4,6-dinitrophenol).

Three selections of johnsongrass (Sorghum halepense (L.) Pers.) were collected from three locations and designated as the N, NS, and S selections, respectively. The selections were studied for growth differences and for a differential response to dalapon (2,2-dichloropropionic acid). The N selection control plants flowered 2 weeks earlier than the other selections. The S selection yielded significantly greater root, rhizome, and total fresh weight than the NS and N selections. The N selection exhibited the most susceptibility to dalapon by producing the shortest plants, the least stem and leaf numbers, and the lowest shoot, root, rhizome, and total fresh weight of the three selections.

This invitational paper on the α-chloroacetamides is the first of a series of historical reports on each of the major classes of chemistry that have been developed for herbicides.

A soil sampler was constructed to collect soil cores in plastic tubes to a depth of 30 cm. This method of sampling prevents loss of soil, minimizes soil contamination, and permits proportional sectioning of the soil core into desirable segments for bioassay or chemical analysis.

The effects of chloride salts of potassium, sodium, ammonium, and lithium and abscisic acid (ABA) on the translocation of 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] in bean (Phaseolus vulgaris L. Var. Stringless Green-pod) seedlings were determined. 14C-labeled 2,4,5-T was injected in the stem tissue at the cotyledonary node in a 1-μl volume along with ABA. The salts were added to the nutrient solution at 20 mM concentrations at the time of 2,4,5-T treatment. Sodium chloride inhibited 2,4,5-T accumulation in the upper portion of the plant; and except for LiCl, the salts tended to increase accumulation in the nutrient solution. LiCl increased 2,4,5-T accumulation in the young shoots and primary leaves and decreased accumulation in the roots and nutrient solution. The effects of ABA on 2,4,5-T translocation were similar to the effects of NaCl but were more pronounced. ABA caused large decreases in 2,4,5-T translocation to the young shoots and primary leaves and increased accumulation in the nutrient solution.

The adsorption-desorption equilibria of fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea] were studied; a slurry technique with soil at 0-bar moisture tension was used. The equilibria established with Bosket very fine sandy loam (VFSL) were evaluated by three equations. The equation best describing the adsorption isotherm was x/m = K1Ce + K2Ce2. Successive equilibrations resulted in a shift in the equilibria toward the adsorbed state, most likeiy due to a physical change in the adsorption capacity of the soil with repeated agitation. Desorption studies with seven additional soils indicated the importance of soil organic matter content in the adsorption-desorption equilibria of fluometuron. The relationship between soil organic matter contents and the adsorption-desorption equilibrium constants was characterized by a highly significant linear correlation (r = 0.93) and the resulting regression equation: K1 = 0.46 + 0.45(O.M.%). Clay content of these soils was not significantly correlated with fluometuron equilibrium constants.

DPX 1840 [3,3a-dihydro-2-(p-methoxyphenyl)-8H-pyrazolo-(5,1-a)isoindol-8-one] modified xylem development in honey mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell] by causing the formation of an essentially fiberless wood. More than 90% of the axial cells on the xylem side of the vascular cambium differentiated as parenchyma. These cells contained large quantities of starch and were similar in structure to the sapwood parenchyma of untreated seedlings. DPX 1840 treatment also brought about the release of basal stem buds and may be potentially useful in woody brush control.

A mixture of microorganisms cultured under nonsterile conditions on propham (isopropyl carbanilate) herbicide as the sole carbon source was tested for its ability to degrade a number of chlorinated and nonchlorinated anilide compounds. In separate tests under pure-culture conditions, species of the microbial mixture reacted individually in a manner similar to the nonsterile whole. The microorganisms grew and respired rapidly on nonchlorinated anilides, but ring chlorination depressed respiration and inhibited growth. Studies on the dimethylphenylureas indicated that the two methyl groups were primarily responsible for the biological stability of these compounds. All other anilides were degraded by hydrolysis of the side chain followed by metabolic degradation of the ring. Appearance of aniline in the medium depended on the relative rates of production by side chain hydrolysis and disappearance by ring degradation. Acylanilides were hydrolyzed more rapidly than carbanilates and chlorinated rings were degraded much more slowly than unchlorinated rings. Chlorination affected rates of ring degradation and microbial respiration in the following order (most rapid to least rapid): 0 > 2,4 > 2,4,5 > 3 > 4 ≥ 3,4. It is proposed that this unexpected degradative sequence might be explained in terms of the degree of microbial toxicity in the system generated by the formation of chloroazobenzenes from chloroaniline intermediates.

Growth room and field studies indicated that coating the seeds of oats (Avena sativa L.) with NA (1,8-naphthalic anhydride) at rates of 0.5 to 1% by seed weight significantly reduced the phytotoxicity of barban (4-chloro-2-butynyl m-chlorocarbanilate) applied to the foliage at rates up to 1.2 kg/ha. Complete protection was obtained when barban was applied at 0.4 kg/ha, the highest rate recommended for the control of wild oats (Avena fatua L.) in cereal crops. Treatment of oat seeds with this antidote did not reduce the herbicidal effect of barban on wild oats grown in the same soil. Thus, coating oat seeds with the antidote may allow the use of barban for the selective control of wild oats in oat crops. NA seed treatment also slightly reduced oat injury from diallate [S-(2,3-dichloroallyl)diisopropylthiocarbamate] and triallate [S-(2,3,3-trichloroallyl)diisopropylthiocarbamate].

Tall fescue (Festuca arundinacea Schreb. ‘Kentucky 31′) drilled into a pasture infested with broomsedge (Andropogon virginicus L.) and fertilized with N, P, and K, eliminated broomsedge after 4 years. In a second experiment, fertilization with N, P, and K increased the density of Kentucky bluegrass (Poa pratensis L.), and broomsedge was gradually reduced over a 5-year period. Fertilization with P and K caused the density of legumes and grass to increase and broomsedge was nearly eliminated after 5 years. In both experiments the old growth of broomsedge was mowed each winter and cattle were then able to graze the new growth of broomsedge. Grazing may have aided in the elimination of broomsedge.

A nonphytotoxic paraffinic oil at 2.5, 5, and 10% (v/v) or a blended alkylaryl sulfonate surfactant at 0.5, 1, and 2% (v/v) did not enhance the activity of propanil (3′,4′-dichloropropionanilide) at 1.7, 3.4, and 6.7 kg/ha applied as a foliage spray in aqueous systems on barnyardgrass [Echinochloa crus-galli (L.) Beauv.] or rice (Oryza sativa L. ‘Starbonnet’). Time and rate of applying propanil affected control of barnyardgrass. Barnyardgrass control and rice yield were best with treatments of 3.4 or 6.7 kg/ha of propanil to four-leaf grass plants. Propanil at 6.7 kg/ha controlled tillering and jointing barnyardgrass well enough to increase grain yields over those of untreated rice.

Field experiments were conducted to study the feasibility of using trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) and nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline] for the selective control of johnsongrass [Sorghum halepense (L.) Pers.] from rhizomes and seed in soybeans [Glycine max (L.) Merr. ‘Lee’]. Both herbicides were incorporated into the soil at 0.56 to 3.36 kg/ha with two disk cultivations immediately after application. Most effective johnsongrass control on Dundee silty clay loam (sicl) followed treatments of nitralin or trifluralin at 1.68 to 3.36 kg/ha, but 2 years or more of continuous treatment were required for acceptable control. Trifluralin at 1.12 and 2.24 kg/ha on Sharkey clay and at 0.56 to 2.24 kg/ha on Bosket fine sandy loam (fsl) provided better average johnsongrass control over a 2-year period than nitralin at the same rates, but soybean yields after both herbicides at the same rates were equal. Immediate incorporation of trifluralin or nitralin in all three soils at 1.12 to 2.24 kg/ha for 2 successive years effectively controlled johnsongrass from rhizomes without soybean injury and with greatly increased soybean yields.

The time course of diphenamid (N,N-dimethyl-2,2-diphenylacetamide) metabolism in tomato (Lycopersicon esculentum Mill. ‘Sheyenne’) was altered by fumigation with 30 pphm (parts per hundred million) of O3. After 2 days 70% of the absorbed diphenamid was metabolized in controls compared with 83% in fumigated plants. Concentrations of N-methyl-2,2-diphenylacetamide (MMDA) were equivalent in both fumigated and control plants. Less glucoside conjugate (MDAG) was present in fumigated plants 2 to 4 days after treatment than in the control plants. Gentiobioside conjugate (MDAGB) increased rapidly in fumigated plants after 0.5 day but not in control plants until after 2 days. Loss of diphenamid from aerated solution was demonstrated. A scheme for diphenamid metabolism is proposed.