The effectiveness of activated charcoal in protecting seedling cotton (Gossypium hirsutum L. ‘Stoneville 213’) from diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] at 1.78 and 3.55 kg/ha was investigated under field conditions over a 5-yr period. Charcoal did not provide adequate protection when applied through the seed hopper box or sprayed in the seed furrow over each hill. Charcoal at 83 and 167 kg/ha applied as a spot over each hill of cotton gave adequate protection. Shallow incorporation of the charcoal significantly reduced the degree of protection. The optimum combination, providing maximum weed control and minimum crop injury, was diuron at 3.55 kg/ha applied over non-incorporated charcoal at 83 kg/ha.

Wild oat (Avena fatua L.) control and wheat (Triticum aestivum L.) injury with barban (4-chloro-2-butynyl m-chlorocarbanilate)-aqueous nitrogen combinations were evaluated in the field and greenhouse. The addition of aqueous nitrogen at volumes as low as 5 L/ha increased wild oat control with barban. The greatest increase in wild oat control with barban-aqueous nitrogen combinations was obtained on soil low in nitrogen. Wild oat control with barban-aqueous nitrogen combinations was not influenced by spray volume or nitrogen source. Aqueous nitrogen applications several days prior to barban were more effective than when the two were applied together. Wheat was generally quite tolerant of barban-aqueous nitrogen combinations; however, some injury was observed in 1974.

The influence of seed age, planting depth, and temperature on the germination and emergence of ivyleaf morningglory [Ipomoea hederacea (L.) Jacq. var. hederacea], white morningglory (Ipomoea lacunosa L.), and entireleaf morningglory (Ipomoea hederacea var. integriuscula Gray) was studied by using pure seed of each taxa that were collected in 1972, 1973, and 1974. Germination of acid-scarified white and entireleaf morningglory seed ranged from 64 to 98% at continuous 20, 25, 30, 35, and 40 C and at an alternating 20/30 C cycle. The ivyleaf morningglory germination range was 50 to 98% at these temperatures, except at 40 C germination was <25%. Germination of nonscarified seed was generally 30 to 60% lower than scarified seed for the three taxa. Germination of seed collected in 1972 for all three taxa was less than 10% with 6 days of exposure to 45 C and 100% relative humidity, and germination of seed collected in 1973 and 1974 ceased with 12 days of exposure. Maximum emergence for all taxa occurred at planting depths of 1.3 and 2.5 cm. Seed age influenced seedling emergence of white morningglory and ivyleaf morningglory but not entireleaf morningglory. Total numbers of seed produced per plant for white, entireleaf, and ivyleaf morningglory were 15,200, 14,600, and 5,800, respectively.

Several soil-applied and two foliar herbicides were evaluated for weed control in established alfalfa (Medicago sativa L.) in two experiments for two consecutive years. Most of the soil-applied herbicides effectively controlled weeds in the first harvest year following application; however, there was little carry-over into succeeding years. Except for the low rate of secbumeton [N-ethyl-6-methoxy-N′ (1-methylpropyl)-1,3,5-triazine-2,4-diamine] in the first alfalfa cutting of 1973, no herbicide treatment significantly increased alfalfa yields over the control plot. In fact, some herbicides caused injury to alfalfa at high rates of application, as did reapplication a second year at the original rate of application.

The addition of simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] wettable powder to water solutions of glyphosate [N-(phosphonomethyl)glycine] in greenhouse studies reduced glyphosate activity on quackgrass [Agropyron repens (L.) Beavu.], corn (Zea mays L.), and beans (Phaseolus vulgaris L.). Atrazine [2-chloro-4-(ethylamino)-6-isopropylamino)-s-triazine] wettable powder reduced glyphosate activity on corn. This antagonism was more pronounced at threshold levels of glyphosate and was overcome by increasing the glyphosate rate. Simazine applied to corn through the soil did not reduce the activity of glyphosate applied to the foliage. Glyphosate activity on corn was reduced equally when glyphosate was mixed with 4.2 kg/ha of commercial simazine wettable powder or an equal amount of the inert ingredients used in the commercial product. When mixtures of glyphosate with either the commercial simazine product or the inert ingredients from the commercial product were centrifuged, the amount of phosphorus (used as a measure of glyphosate) in the supernatant was reduced by 10 to 20%. When the supernatants of the various mixtures were applied to bean plants, the reduced phytotoxicity from the mixtures was comparable to the antagonism noted in previous experiments. These data support the conclusion that the reduction in glyphosate phytotoxicity from mixing with atrazine or simazine wettable powders is due to a physical binding within the spray solution rather than from biological interactions within the plant.

Yellow foxtail [Setaria glauca (L.) Beauv.], giant foxtail (Setaria faberi Herrm.), giant green foxtail [Setaria viridis var. major (Gaud.) Posp.], robust white foxtail (Setaria viridis var. robusta-alba Schreiber), and robust purple foxtail (Setaria viridis var. robusta-purpurea Schreiber) were grown from seed in pure stands in sand-soil nutrient solution cultures at various nitrogen levels. Within taxa dry weight of herbage differed significantly with nitrogen level, but dry weight of roots did not. Yellow foxtail produced more leaf area than the other four taxa regardless of nitrogen level. At the low nitrogen level, yellow foxtail produced significantly more root mass (dry weight) than the other taxa; giant foxtail was second in root-mass production. The order of root-mass production was the same at medium and high nitrogen levels, but only at a 12-h photoperiod. At a 16-h photoperiod, root production was equal in yellow foxtail and giant foxtail and was significantly greater in these taxa than in giant green foxtail, robust white foxtail, or robust purple foxtail. Generally similar relationships were evident in the root: shoot ratios. The chances for survival with giant foxtail taxa should be better for yellow foxtail than for the other foxtail taxa since yellow foxtail produced more root mass even at low nitrogen fertility, a condition common in undistrubed sites such as roadsides and fencerows.

Key metabolic enzymes and germination were studied in developing and mature, dormant and nondormant prickly sida (Sida spinosa L.) seeds. Isocitrate dehydrogenase, glucose-6-phosphate dehydrogenase, fructose-1,6-diphosphatase, and phosphofructokinase activities were determined in developing and mature prickly sida seeds. Developing seeds less than 7 days after anthesis and at 17 days or greater after anthesis were unable to germinate. The 7-day-old seeds lacked all but fructose-1,6-diphosphatase activity. The 17-day-old seeds demonstrated all enzyme activities but failed to germinate because dehydration had occurred and seeds were unable to imbibe sufficient water without an afterripening period. Comparison of enzyme activities of dormant and nondormant seeds on incubation showed that only glucose-6-phosphate dehydrogenase was considerably different within the first 8 h of incubation. Nondormant seeds had considerable glucose-6-phosphate dehydrogenase activity before germination (radical protrusion at 8 h), suggesting an active pentose phosphate pathway.

Field experiments were conducted for a 3-yr period to determine the feasibility of planting an alternate crop on fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea] treated cotton land in event that an adequate cotton (Gossypium hirustum L.) stand fails to materialize. Fluometuron treatments were 1.7 kg/ha on a treated area basis as a banded application, and 1.7 and 3.4 kg/ha as a broadcast application. Grain sorghum [Sorghum bicolor (L.) Moench ‘AKS-614’, ‘Excel’ and ‘BR 64’] and soybeans [Glycine max (L.) Merr. ‘Dare’ and ‘Lee 68’] were planted 3, 6, and 9 weeks after fluometuron application. Grain sorghum and soybean tolerance to fluometuron residues varied between locations. Very little injury occurred on the Sequatchie loam in Knoxville, Tennessee, but considerable injury occurred on the Memphis silt loam at Milan, Tennessee. The differences were attributed to higher rainfall during the first 3-week period and to higher organic matter and higher sand content at Knoxville. Nevertheless, at Milan, grain sorghum was successfully grown 3 weeks after the 1.7 kg/ha banded application, 6 weeks after the 1.7 kg/ha broadcast application and 9 weeks after the 3.4 kg/ha application. Soybeans, also at Milan, were partially injured when planted between the fluometuron (1.7 kg/ha) treated bands 6 weeks after application and 9 weeks after application when planted on the 1.7 kg/ha broadcast-treated areas.

Field and greenhouse tests were conducted from 1974 to 1976 to determine the most effective rate and number of applications of bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-(4)3H-one 2,2-dioxide] for the control of six morningglory (Ipomoea) species. Growth chamber studies were conducted to determine photosynthesisrespiration equilibrium points (PRE-points) on two morningglory species. These units were used to measure the duration of the phytotoxic effect of bentazon on these morningglories from both single and repeat applications. Declining PRE-points indicated declining bentazon toxic activity within the plant. A treatment of two applications of bentazon at 0.84 kg/ha applied at a 4-day interval beginning with 2-week-old morningglory plants was optimal for maintaining a high PRE-point level. In field and greenhouse studies the greatest toxicity, regardless of morningglory species, occurred with bentazon at 0.84 or 1.12 kg/ha applied at 14 days and repeated at 28 days after emergence and 0.56 kg/ha applied three times with the first application made 14 days after emergence. Differences in susceptibility of the individual species indicated the importance of proper species identification before bentazon applications.

For effective biological control through augmentation, Bactra verutana Zeller, would have to be released against purple nutsedge (Cyperus rotundus L.) in May and June when temperatures are cooler than they are from late July through September when maximal natural populations of this biological control agent occur. Bactra larvae exposed to simulated mid-May (24/13 C) and mid-June (29/18 C) temperature regimes developed more slowly than larvae exposed to the mid-July (32/26 C) temperature regime, but nutsedge plant growth was also slower. Thus, the relative amounts of feeding injury were similar at all three regimes. Larval feeding generally increased the number of shoots slightly, but not significantly, reduced significantly the production of inflorescences, and reduced the weight of total dry matter produced between 28 and 49%.

Glyphosate [N-(phosphonomethyl)glycine] (30, 125, 250 mg/L) in petri dishes had no effect on germination of prickly sida (Sida spinosa L.), velvetleaf (Abutilon theophrasti Medic), barnyardgrass [Echinocloa crus-galli (L.) Beauv.] and johnsongrass [Sorghum halepense (L.) Pers.] seeds, but additional experimentation indicated that glyphosate stimulated germination of redroot pigweed (Amaranthus retroflexus L.) seeds. Paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) (30, 125, 250 mg/L) did not affect germination of the three broadleaf species, but inhibited johnsongrass and barnyardgrass germination. In the greenhouse, soil surface applications of glyphosate (1.1, 2.2, 9.0 kg/ha) did not significantly affect emergence of these five weed species when they were on or beneath the soil surface at time of treatment. Paraquat (same rates) did not affect broadleaf weed emergence but some rates inhibited grass weed emergence when the seeds were treated while on the soil surface. It is unlikely that normal field use rates of glyphosate will influence weed emergence; whereas paraquat may inhibit the emergence of some grass weeds if the herbicide contacts seeds on the soil surface.

The effect of fall frost on the activity of glyphosate [N-(phosphonomethyl)glycine] on alfalfa (Medicago sativa L. ‘Vernal’) and quackgrass [Agropyron repens (L.) Beauv.] was studied in a room of the Biotron, a controlled environment facility of the University of Wisconsin, and in the field in the fall. In a Biotron time-course study, the most effective day of treatment for quackgrass control was the day after the first frost. Quackgrass plants treated the morning after frost had significantly higher uptake and translocation of glyphosate (93%, 55%) than plants treated 4 days before frost (71%, 32%) and greater translocation than plants treated 5 days after frost (24%). In the field, glyphosate was most active on quackgrass when applied the morning after the first frost of the fall. Control of quackgrass treated with 0.4 kg/ha of glyphosate increased from 10% when treated 4 days before the first frost to a maximum of 91% when treated the day of the first frost. No significant effects of frost in decreasing glyphosate toxicity to alfalfa were found. These results minimize the possibility of using this herbicide to remove quackgrass from alfalfa.

Karbutilate [tert-butylcarbamic acid ester with 3(m-hydroxypheny)-1, 1-dimethylurea], formulated as a ball 1.34 cm in diameter, was applied to brush-infested rangeland with fixed-wing aircraft and in a grid pattern by hand at an average density of four balls/12.4 m2 (1.83-m spacing). Control of woody plants with karbutilate applied by hand in an exact grid pattern was not different from aerial applications at the same rate. Based on evaluations at least 24 months after application, karbutilate at 0.56 or 1.12 kg/ha did not control honey mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell] in the subhumid Post Oak Savannah or semiarid Rolling Plains of Texas. At 2.24 kg/ha, canopy reduction of honey mesquite averaged 70% with 20 to 25% of the population killed. Post oak (Quercus stellata Wangenh.), blackjack oak (Quercus marilandica Muenchh.), yaupon (Ilex vomitoria Ait.), or winged elm (Ulmus alata Michx.) in Post Oak Savannah were not killed by 2.24 kg/ha. Karbutilate eliminated all vegetation in a 25 to 45-cm diameter circle, depending on concentration of active ingredient in the ball, the year of treatment regardless of vegetation region. The bare areas were revegetated within 2 yr following application in the Post Oak Savannah. However, bare areas in sodgrasses, primarily tobosa [Hilaria mutica (Buckl.) Benth.] and buffalograss [Buchloe dactyloides (Nutt.) Engelm.], where 1.12 and 2.24 kg/ha were applied averaged 20 to 30 in diameter, respectively, 32 months after application to sandy clay loam in the Rolling Plains.

In the greenhouse, the methyl ester of diclofop {2-[4-(2,4-diclorophenoxy)phenoxy] propanoic acid} as a postemergence application at 1.1 kg/ha ai did not affect the growth of the seven dicotyledonous crops with the exception of slight injury to yellow [white] mustard (Brassica hirta Moench). Of the 13 gramineous species, corn (Zea mays L.), green foxtail [Setaria viridis (L.) Beauv.], oats (Avena sativa L.) wild oats (Avena fatua L.), sorghum [Sorghum bicolor (L.) Moench], and timothy (Phleum pratense L.) were rated highly susceptible, while barley (Hordeum vulgare L.), bromegrass [smooth brome] (Bromus inermis Leyss.), durum wheat (Triticum durum Desf.), intermediate wheatgrass [Agropyron intermedium (Host) Beauv.], Russian wild ryegrass (Elymus junceus Fisch.), triticale (X Triticosecale Wittmack), and wheat (Triticum aestivum L.) were relatively tolerant. Residue of diclofop in the soil partially controlled green foxtail which was seeded 3 weeks after herbicide application. Whether applied to wild oat shoots or roots, diclofop affected the entire plant, but growth reduction was great when applied to the shoots. Field results confirmed that foliar application gave the best weed control resulting in larger wheat yield increases. Wild oat control was greatly enhanced when an adjuvant was added to diclofop. This enhanced herbicidal activity appeared to have no effect on tolerance of barley at 0.8 kg/ha nor wheat at 1.1 kg/ha. Increasing the temperature from 12 to 28 C decreased wild oat control from diclofop at 1.1 kg/ha. In the field, diclofop at rates ranging from 0.8 to 2.2 kg/ha gave good control of wild oats and green foxtail resulting in significantly increased wheat yield compared to the checks. However, barley yield increases were obtained only at the rates from 0.8 to 1.1 kg/ha, indicating that at the higher rates barley was less tolerant than wheat. The 0.6 kg/ha rate with an adjuvant gave adequate weed control and significant barley yield increases over the checks, when evaluated on five barley cultivars.

A small enclosure was developed for isolating areas of submersed weeds within bodies of open water and for evaluating the efficacy of herbicides. The enclosure can be easily dismantled and transported between lakes and can be moved readily by flotation as a unit within a lake. Its use will permit smaller research plots, less herbicide per treatment, more plots within a uniform environment, and more accurate assessment of the relationship between herbicide concentration and length of exposure than are possible with the more commonly used techniques.

The absorption of 14C-dipropetryn (2-ethylthio-4,6-bis-isopropylamine-s-triazine) and 14C-prometryn [2,4-bis(isopropylamino)-6-(methylthio)-s-triazine] by roots of intact seedlings of corn (Zea mays L. ‘Iowa Chief) and oats (Avena sativa L. ‘Cimarron’) was very extensive and occurred to about the same degree in both species after application to the root medium. The translocation of 14C-label of dipropetryn to the shoots was low in corn as compared to oats. Prometryn 14C-label was more readily translocated to the tops of corn than dipropetryn and was more readily translocated in oats than corn. Dipropetryn 14C-label entered excised leaves through the transpiration stream during a short exposure period and translocated to a greater extent in oats than in corn. The 14C-label of dipropetryn became immobilized in excised leaves after about 4 h. The 14C-label of prometryn was initially more mobile in excised leaves of oats than corn. However, translocation of the 14C-label of prometryn continued in both species during 10 h of treatment and there was very little difference in the final distribution pattern. DNP (2,4-dinitrophenol) did not affect the distribution pattern of the 14C-label of dipropetryn or prometryn in corn after 10 h treatments.

The uptake, translocation, and metabolism of the herbicide fluridone 1-methyl-3-phenyl-5-[3-(trifluoromethyl)phenyl]-4(1H)-pyridinone was studied in cotton (Gossypium hirsutum L. ‘Stoneville 213’) (fluridone tolerant) and corn (Zea mays L. ‘Migro 5040’), soybean [Glycine max (L.) Merr. ‘Calland’], and rice (Oryza sativa L. ‘Nato’) (fluridone susceptible). Uptake studies with 14C fluridone demonstrated that all species absorbed radioactivity with rice having the highest concentration. Equivalent concentrations of radioactivity were observed in corn, cotton, and soybean. Absorbed fluridone was retained primarily in the roots and the basal region of the stem of cotton, while in the herbicide susceptible species fluridone was readily translocated into the shoots. No appreciable metabolism of fluridone was observed in the roots or shoots of cotton and soybean. Tolerance of cotton to fluridone was primarily attributed to the limited translocation of the compound.

Infrared spectroscopy was used to study the hydrolysis of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] upon interaction with homoionic soil colloids. Montmorillonite, an allophanic soil clay, and a montmorillonitic Coker soil clay were saturated with H+, Al3+, Cu2+, and Ca2+ and treated with atrazine and hydroxyatrazine [2-hydroxy-4-(ethylamino)-6-(isopropylamino)-s-triazine]. Hydrolysis of atrazine was evaluated by the presence of a strong hydroxyatrazine carbonyl absorption band at 1745 cm-1. The H+- and Al3+-saturated montmorillonite and montmorillonitic Coker soil clay promoted atrazine hydrolysis while Ca2+- or Cu2+-saturated montmorillonite did not. A small degree of atrazine hydrolysis was detected in the Cu2+-Coker soil clay. Dehydration of Ca2+- or Cu2+-Coker soil clay after equilibration with atrazine increased the hydrolysis of atrazine. The allophanic soil clay did not catalyze the hydrolysis of atrazine when the exchange complex was saturated with H+, Al3+, Ca2+, or Cu2+. Moreover, Al3+-allophane was not sufficiently acidic to protonate hydroxyatrazine. Thus, a major difference exists between soil allophanic colloids, montmorillonitic soil clays, and montmorillonite as catalysts in the protonation and hydrolysis of atrazine.

Field studies on the persistence of simazine [2-chloro-4,6-bis(ethylamino)-s-triazine] showed less persistence under no-tillage corn (Zea mays L. ‘Pioneer 3369A’) culture than conventionally tilled corn. Bioassay studies conducted in the greenhouse using oats (Avena sativa L. ‘Compact’) as indicator crop showed the lowest level of simazine remaining in soils of low pH (5.4 and lower). Persistence of simazine in the soil increased with increasing soil pH.

The Persistence of substituted dinitroaniline herbicides in soil varied widely. First-order kinetics were used to describe the dissipation rates. Half-lives of the herbicides in moist soil ranged from 29 to 124 days in two soil types under greenhouse conditions. Flooding the soil significantly increased the dissipation rate of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), fluchloralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl)aniline], profluralin [N-(cyclopropylmethyl)-α,α,α-trifluoro-2,6-dinitro-N-propyl-p-toluidine], and pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine]. Dissipation rates of dinitramine (N4,N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine) and butralin [4-(1,1-dimethylethyl)-N-(1-methylpropyl)-2,6-dinitrobenzenamine] were affected to a lesser extent by flooding. Volatilization of trifluralin, fluchloralin, and ethalfluralin [N-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4-(trifluoromethyl)benzenamine] from Bosket sandy loam was reduced by flooding when compared to volatilization from the same soil with a moisture content equivalent to field capacity. Pendimethalin exhibited low volatility. The effect of flooding on dissipation rates is apparently not due to increased volatilization.