Johnsongrass [Sorghum halepense (L.) Pers.] regrowth was used as an index for penetration and translocation of dalapon (2,2-dichloropropionic acid) with and without adjuvants under different environmental conditions. Johnsongrass control with dalapon at 1.12 kg/ha without surfactant decreased as air temperature increased from 16 to 27 to 38 C. Plants at 16 and 27 C with 100% relative humidity (RH) were more susceptible to dalapon without surfactant than were plants at 35% RH. The presence of 1% surfactant in dalapon solutions increased johnsongrass control above that of dalapon alone at 27 and 38 C regardless of RH. Adding 1% surfactant and maintaining plants at 100% RH and 38 C resulted in significantly less johnsongrass control than that at 35% RH and 38 C. The addition of 0.1 M KH2PO4 to mixtures of dalapon + surfactant restored effectiveness at 100% RH and 38 C. Dalapon applied without surfactant was more injurious to johnsongrass grown with 40% soil moisture than with 25% soil moisture regardless of air temperature or RH. When plants were maintained at 27 or 38 C with 25% soil moisture, 0.1 M KH2PO4 + surfactant was more beneficial than surfactant alone in increasing dalapon toxicity to johnsongrass. At 40% soil moisture, johnsongrass control with dalapon + 1 % surfactant was not improved with the addition of KH2PO4 regardless of air temperature.

Navy bean (Phaseolus vulgaris L.) seedlings grown in soil treated with EPTC (S-ethyl dipropylthiocarbamate) were more susceptible to root rot caused by Fusarium solani (Mart.) Appel and Wr. f. phaseoli (Burk.) Snyd. and Hans. than were control seedlings. The navy bean line ‘RRR041,’ which is moderately resistant to root rot, did not show reduced growth when grown in soil infested with F. solani and treated with EPTC. None of the several herbicides tested increased F. solani chlamydospore virulence when grown on potato dextrose agar supplemented with herbicides. No herbicide tested increased F. solani hyphal development in liquid culture or soil. Dinoseb (2-sec-butyl-4,6-dinitrophenol) reduced hyphal development by the greatest amount. Scanning electron micrographs indicated that navy bean plants grown in EPTC had altered hypocotyl surfaces. EPTC and dinoseb increased the exudation of electrolytes, amino acids, and sugars from root and hypocotyl tissue.

Laboratory studies were conducted to measure the relative volatility of triallate [S-(2,3,3-trichloroallyl) diisopropylthiocarbamate] from soils and to determine the effect of surfactants on triallate mobility. Significant volatilization occurred from continuously moist soils under constant air exposure but triallate did not volatilize more rapidly than herbicides which do not respond to incorporation. Volatilization rates from Ray silt soil fell in the order of propachlor (2-chloro-N-isopropylacetanilide) > triallate > alachlor [2-chloro-2′, 6′-diethyl-N-(methoxymethyl)acetanilide] and from Drummer silty clay loam were propachlor > alachlor > triallate. In suspension studies soils reversibly adsorbed 93 to 98% of the triallate in aqueous solution. With soil at field moisture capacity, the concentration of triallate in soil solution was 13 ppbw without surfactant and 14 ppbw with 3 parts emulsifier blend to 1 part of triallate (w/w). With this level of emulsifier 92% of triallate applied to the soil surface remained in the upper 3 cm of soil following a 15.2-cm simulated rainfall. Without surfactant 99% remained in the upper 3 cm of soil. Lower triallate mobility in moist soils observed in this study coupled with the strong dependence of triallate bioactivity as reported by others strongly suggests that deactivation by dry surface soils rather than volatility is primarily responsible for the triallate response to incorporation.

Seedlings of fifteen different cultivars of tomato (Lycopersicon esculentum Mill.) varied greatly in tolerance to metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H) one] applied at a concentration of 0.5 mg/L in quartz sand nutrient culture during the three-true-leaf stage. Tolerance increased with seedling age, but acceptable tolerance was observed about 6 days earlier in the tolerant ‘Fireball’ compared to the susceptible ‘Heinz 1706′. Root uptake and acropetal translocation of metribuzin-carbonyl-14 C was similar in 2-week-old seedlings of susceptible Heinz 1706 and tolerant Fireball seedlings. Differential tolerance was related to the rate of detoxification by metabolism within the tomato leaves, which was approximatley two-fold greater in the tolerant Fireball seedlings.

Phytotoxicity of glyphosate (N-(phosphonomethyl) glycine), applied at 0, 0.56, 1.12, 1.68, 2.24 and 4.49 kg ai/ha to uniform, naturally growing quackgrass, [Agropyron repens (L.) Beauv.] plants, was studied with the electron microscope. Visible damage (yellowing of the leaves) to the plants was observed at the 2.24 and 4.49 kg ai/ha dosage rates within 72 hr. Similar damage became evident 120 hr after treatment at the 0.56 to 1.68 dosages. Leaf discs (1 mm in diameter) were harvested at 24, 48, 96, and 192 hr and prepared for electron microscopy by standard techniques. Cellular damage could be detected at all dosage rates as early as 24 hr after treatment. The type of damage observed was partial to complete disruption of the chloroplast envelope, and swelling of the rough endoplasmic reticulum (RER) with a subsequent formation of vesicles. With loss of integrity of the envelope, the chloroplast became completely disrupted with increased time. Other organelles within the cell were also destroyed.

The absorption, translocation, and metabolism of 14C-profluralin [N-(cyclopropylmethyl)-α,α,α-trifluoro-2,6-dinitro-N-propyl-p-toluidine] and 14C-dinitramine (N4,N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine) in sorghum [Sorghum bicolor (L.) Moench ‘RS6–12′], barnyardgrass [Echinochloa crus-galli (L.) Beauv.], soybean [Glycine max (L.) Merr. ‘Dare’], and Palmer amaranth (Amaranthus palmeri S. Wats.) were determined after treatment with 14C-labeled herbicides in nutrient solution for 24 hr at 16 or 38 C. 14C-profluralin accumulated in roots to a greater extent at 16 C, while metabolism was greatest at 38 C. Very little 14C-profluralin was translocated to the tops of plants. Conversely, 14C-dinitramine accumulated in the tops of plants to a greater extent at 38 C. Metabolism was not greatly affected by temperature. These effects may relate to excess toxicity of profluralin at 16 C and dinitramine at 38 C in species which normally exhibit resistance to the herbicides.

Over a 3-yr period 10 herbicides were tested alone or in combination for control of weeds and for effects on growth of nursery stock in containers. Annual bluegrass (Poa annua L.) was controlled by norea [3-(hexahydro-4,7-methanoindan-5-yl)-1,1-dimethylurea], alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide], and combinations of diphenamid (N,N-dimethyl-2,2-diphenylacetamid), trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), and nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline] plus simazine [2-chloro-4,6-bis(ethylamino)-s-triazine]. Bittercress (Cardamine oligosperma Nutt.) was controlled by simazine, oxadiazon [2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-Δ2-1,3,4-oxadiazolin-5-one], and norflurazon [4-chloro-5-(methylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone]. Mouseear chickweed (Cerastium vulgatum L.) was controlled by dichlobenil (2,6-dichlorobenzonitrile) and norflurazon, and common groundsel (Senecio vulgaris L.) was controlled by dichlobenil and norflurazon. Some of the treatments decreased growth of certain nursery cultivars.

Single and repeat applications of herbicides or herbicide combinations were made over-the-top of young cotton (Gossypium hirsutum L.). DMSA (disodium methanearsonate) and MSMA (monodosium methanearsonate) applied 4 or 8 weeks after emergence had less effect on cotton yield, boll components, and fiber properties than did applications made 12 weeks after emergence. Most single, over-the-top applications of DSMA, fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea], or DSMA with fluometuron 4 weeks after emergence did not affect cotton yield, boll components, or fiber properties. One or two applications of diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] or prometryn [2,4-bis(isopropylamino)-6-(methylthio)-s-triazine] alone, or with DSMA, reduced cotton yields. Applications of 1.1 and 2.2 kg/ha of fluometuron over-the-top of cotton 2 to 8 weeks after emergence did not affect cotton yields, boll components, or fiber properties.

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.

Renovation of common bermudagrass [Cynodon dactylon (L.) Pers.] turf to either ‘Tifway’ or ‘Tifdwarf’ bermudagrasses, zoysia (Zoysia japonica Steud. x Zoysia tenuifolia Willd. ex Trin. ‘Emerald’) or centipedegrass [Eremochloa ophiuroides (Munro) Hack.] was undertaken with the aid of herbicides. Glyphosate [N-(phosphonomethyl)glycine] applied to common bermudagrass turf followed by treatments of MSMA (Monosodium methanearsonate) + 2,4-D[2,4-dichlorophenoxy)acetic acid] alone or in sequence with DCPA (dimethyl tetrachloroterephthalate) reduced the cover of common bermudagrass in renovated Tifway or Tifdwarf bermudagrass turf. Dalapon (2,2-dichloropropionic acid) applied alone or in sequence with DCPA, MSMA + 2,4-D, or DCPA + MSMA + 2,4-D also reduced coyer of common bermudagrass in some plantings. Paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) and cacodylic acid (hydroxydimethylarsine oxide) did not reduce the cover of common bermudagrass in turf renovations. Slower growing Emerald zoysia and centipedegrass could not compete with the common bermudagrass that escaped the herbicide applications and renovation was unsuccessful.

In the greenhouse, postemergence treatments of 1.12 kg/ha of HOE 22870 [4-(4′-chlorophenoxy)-phenoxy-α-propionic-isobutylester] or HOE 23408 methyl 2-[4-(2,4-dichlorophenoxy)phenoxy] propanoate were applied to three perennial weeds (two grasses and one sedge) and to 27 species or varieties of annual grasses (crops and weeds). The perennials were resistant to both compounds, but control of the seedling grasses ranged from 0 to 100%, indicating the potential of controlling certain grass weeds in certain grass crops, as well as in broadleaf crops. Generally, the response of a given species was similar for both compounds. However, on some grasses one compound was considerably more effective than the other. Seven species or varieties of foxtail (Setaria spp.) were treated with various rates of either compound. Differential responses were observed, but it appeared that all the foxtail species or varieties studied should probably be controllable with HOE 23408. All but yellow foxtail [Setaria lutescens (Weigel) Hubb.], should probably be controllable with HOE 22870.

The area influenced by individual herbicide granules was determined by rating control of weeds planted in fixed patterns around granules. The area of foxtail millet [Setaria italica (L.) Beauv.] controlled by alachlor [2-chloro-2′,6′diethyl-N-(methoxymethyl) acetanilide] was larger than the area of velvetleaf (Abutilon theophrasti Medic.) controlled by atrazine [2-chloro-4(ethylamino)-6-(isopropylamino)-s-triazine]. Control was most consistent when granules and seeds were near the same depth and was most variable when granules were on the soil surface. Control of foxtail millet with alachlor increased with increasing soil moisture, with decreasing granule depth, and with increasing seed depth. At low soil moisture, control of velvetleaf with surface-applied atrazine was better with simulated rain than with subirrigation. When soil moisture was high and atrazine granules were placed 1-cm deep, control was better with subirrigation. The area-of-influence, or the control (y) as function of distance (x) from granule, was described by y = 10e-A(x-B)2. The radius-of-control (ROC), defined as the radius of the circular area around a granule within which weeds are effectively controlled, was estimated from this relationship.

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.

The relative volatilities of various technical and formulated ester and amine salts of 2,4-D [(2,4-dichlorophenoxy)acetic acid] were determined in a closed air-flow system consisting of a volatilization chamber and an ethylene glycol trap. The system was operated at a flow rate of 28.8 L/hr and a temperature of 30 C. Trapped herbicide vapor was analyzed by gas chromatography. The relative volatilities of technical grade iso-propyl, butyl, propylene glycol butyl ether, and iso-octyl esters, were 56, 25 to 38, 4, and 1, respectively. The relative volatilities of various formulated esters and amines were of the magnitude of 440:33:1 for the high volatile, low volatile, and amine salts, respectively.

The effects of soil organic matter, clay, extractable Al, cation exchange capacity, and pH on the adsorption of picloram (4-amino-3,5,6-trichloropicolinic acid) from aqueous and surfactant solutions were investigated. Linear adsorption isotherms for the soils were obtained with the Freundlich equation. Of the five soil properties investigated, Freundlich K values correlated with extractable Al and clay content. Picloram adsorption from aqueous solutions and from the non-ionic and anionic surfactant solutions was greater on the soils at pH 5 than at pH 7. The anionic surfactant competed with picloram for adsorption sites on the soils at pH 5. Picloram adsorption from solutions containing 0.1 and 1% cationic surfactant was greater than that from aqeuous and anionic and nonionic surfactant solutions. Picloram adsorption from the 10% cationic surfactant solution was similar on soils with pH 5 and 7 and increased with decreased organic matter content.

The comparative morphological development of six johnsongrass [Sorghum halepense (L.) Pers.] ecotypes was studied over a 10-week period. Three of the ecotypes were previously shown to be susceptible to dalapon (2,2-dichloropropionic acid) while others were resistant to the herbicide. The production of primary culms varied from 5.0 to 9.3 per plant system, and secondary culms ranged from 7 to 24 per plant system. Plant heights varied nearly two-fold, and the number of individual rhizomes produced by different ecotypes varied three-fold. Susceptible ecotypes from Georgia, Washington, and Illinois produced more rhizome nodes and higher dry and wet weights of culms and rhizomes than resistant ecotypes from Mississippi, Louisiana, and California. Ecotypes most resistant to dalapon had longer rhizome internodes and higher water content in culms and rhizomes than susceptible strains. Differences in anatomy and growth support the hypothesis of the existence of johnsongrass ecotypes, but the results were not consistent with the susceptibility of ecotypes to dalapon.

When peanuts (Arachis hypogaea L.) were not kept weed-free, a single cultivation 4 weeks after emergence increased yields substantially over those of non-cultivated peanuts. Cultivation had no effect, however, when peanuts were maintained weed-free for 4 or 8 weeks. The length of the weed-free periods, cultivation, and the presence or absence of peanuts all strongly influenced the density of the sicklepod (Cassia obtusifolia L.) plants which grew above the canopy of peanut foliage. Peanut foliage, which was released from weed-free maintenance at 8 weeks but then competed with sicklepod until harvest, reduced the green weight of sicklepod 95 to 98% thus illustrating the competitive capacity of the peanut plant. Moderate stands of Florida beggarweed [Desmodium tortuosum (Sw.) DC] did not markedly affect yield of peanuts. Application of a growth regulator, succinic acid, 2,2-dimethylhydrazide (SADH), did not influence weed competition or yield of in-shell peanuts consistently at any of the three locations. Quality analyses showed that treatment variables did not modify the taste of peanuts; however, in some experiments, components of the market grade of in-shell peanuts were changed by SADH, cultivation, length of the weed-free period, and cultivation X length of the weed-free period.

Control of spurred anoda [Anoda cristata (L.) Schlecht.] in the greenhouse was less than 75% after 28 days with preplant incorporated herbicides except dinitramine [N4,N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine] which gave 88 to 94% control. In greenhouse and field studies with cotton (Gossypium hirsutum L. ‘Coker 210′) preemergence applications of norflurazon [4-chloro-5-(methylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone] controlled 93 to 100% of the spurred anoda 4 weeks after application. Control with postemergence applications of fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-toly)urea] was 46.0 to 92.5%; 90.7 to 100% with prometryn [2,4-bis(isopropylamino)-6-(methylthio-s-triazine]; and 100% with methazole, [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione]. Preemergence applications of norflurazon plus fluometuron, prometryn, or methazole applied postemergence controlled 93, 97, and 100% of spurred anoda, respectively. Fluometuron plus the same three postemergence treatments controlled 63, 95, and 88% of spurred anoda, respectively. Results of our tests suggest that the best control of spurred anoda can be obtained in cotton by a combination of norflurazon applied preemergence at 1.68 kg/ha followed by two postemergence applications of either fluometuron at a rate of 2.24 kg/ha, prometryn at a rate of 1.68 kg/ha, or methazole at a rate of 1.68 kg/ha.

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.