Field and greenhouse experiments evaluated interactions of soil-applied insecticides and imazaquin and imazethapyr on growth and development of cotton. Imazaquin and imazethapyr were applied PPI at 0 to 6 and 0 to 16 g ae ha−1, respectively, in the greenhouse (plus a no-insecticide control), and 0 to 72 g ha−1 in the field in combination with aldicarb, disulfoton, and phorate (without a no-insecticide control) applied in the seed furrow. Cotton shoot fresh weight in the greenhouse experiment decreased linearly as herbicide rates increased. Greater reductions in shoot fresh weight were noted with imazaquin than with imazethapyr. Compared with no insecticide, the methylcarbamate insecticide aldicarb and the organophosphate insecticides disulfoton and phorate did not affect cotton response to either herbicide. In the field, cotton injury increased while stand, yield, and maturity decreased as herbicide rates increased. Delayed maturity was due to a lower percentage of bolls produced on sympodia from main stem nodes four to nine. Imazaquin caused greater injury, greater reductions in stand, greater delays in maturity, and lower yields than did imazethapyr. Earlier maturity was noted with aldicarb-treated cotton. Compared with aldicarb, disulfoton and phorate did not alter cotton response to imazaquin or imazethapyr.

Application of NH4+-bearing fertilizer in field and pot experiments increased triallate [S-(2,3,3-trichloroallyl)diisopropylthiocarbamate] activity on oats (Avena sativa ‘Harmon’). The effect was consistent in the growth chamber, but field results were more variable, depending on soil moisture and temperature conditions. Because the pot experiments showed that the major effect was in shoot-zone-treated soils, the increased triallate activity was attributed to a reduction in triallate adsorption to the soil colloids. However, a smaller effect was measured in root-zone-treated soil, thus a physiological effect is also possible.

Field experiments were conducted in 1991, 1992, and 1993 to evaluate the dissipation and carryover potential of atrazine from starch-encapsulated (SE) and commercial formulations (CF). Formulation was not a significant factor in atrazine dissipation at any application rate. The dissipation time required to reach one-half of the original concentration (DT50) was measured for each formulation. The atrazine DT50 combined over all years (1991 to 1993) and rates (1.1 to 3.4 kg ai ha−1) was 7 wk for the CF, 10.3 wk for the SE large particles (0.85 to 1.4 mm), and 8.2 wk for the SE small (0.425 to 0.85 mm). Oat injury in the spring of 1992 from all rates of both SE formulations applied in 1991 was greater than that from the CF formulation. Increased oat injury from SE formulations was attributed to more atrazine present in the top 0 to 8 cm of soil compared to that for the CF. Despite significant oat injury from the 1991 application, no injury was observed on soybeans planted in 1992. Soybeans planted in 1993 and 1994 also showed no injury from the respective applications. These findings suggest that the potential for atrazine carryover from starch-encapsulated formulations was not greater than that from the commercial formulation.

Greenhouse and growth chamber experiments were conducted to determine the reasons for stunted growth and yield suppression of corn noticed sometimes in nicosulfuron-treated corn fields infested with heavy population of johnsongrass. Results indicated that in the absence of johnsongrass, nicosulfuron applied broadcast POST at 35 g ai ha−1 had no effect on corn. However, growth reduction of corn occurred when nicosulfuron-treated johnsongrass and corn were allowed to share the same rooting medium with their root systems intermingled. The reduction in growth was even greater when corn foliage or the soil surface were also treated with johnsongrass. The extent of growth reduction of corn growing with nicosulfuron-killed johnsongrass depended on weed density and herbicide application rate. Greater growth reductions occurred at four johnsongrass plants per pot compared to two and at a higher application rate of 100 μg nicosulfuron per plant. In general, johnsongrass killed by nicosulfuron appeared to be more phytotoxic to corn than plants killed by paraquat. Nicosulfuron provided excellent control of johnsongrass and improved corn growth by two to three times that of not controlling johnsongrass, but it could not elevate corn growth to the level obtained when johnsongrass was controlled by paraquat or in the absence of interference from johnsongrass.

Herbicide treatments of 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron), 2,4-bis(isopropylamino)-6-(methylthio-s-triazine (prometryne), or methyl ester of 3-amino-2,5-dichlorobenzoate (chloramben ester) were applied preemergence to soybean (Glycine max (L.) Merr. ‘Dare’ or ‘Bragg’) plots previously treated with S-propyl dipropylthiocarbamate (vernolate), α,α.α,-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin), or 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin). Sequential treatments of vernolate with linuron, prometryne, or chloramben ester controlled weeds more effectively in soybeans than did trifluralin or nitralin applied with the same preemergence treatments. Soybean injury was not severe enough to reduce seed yields in any year. Yields were greater in 1970 when soybeans were treated with vernolate than when treated with either trifluralin or nitralin. Soybean yields also were greater in 1970 when treated with chloramben ester than when treated with linuron or prometryne. In 1969 when soybeans were planted in a sandy loam, prometryne reduced stands more than did linuron or chloramben ester.

Field studies were conducted at Dekalb and Urbana, IL, in 1995 and 1996 to evaluate the effectiveness of sethoxydim for giant foxtail control in sethoxydim-resistant (SR) corn. Experiments studied sequential and total postemergence applications of grass herbicide standards compared to sethoxydim. Additional studies evaluated the compatibility of sethoxydim with postemergence broadleaf herbicides. Metolachlor plus atrazine and metolachlor followed by dicamba plus atrazine gave at least 88% control of giant foxtail at both locations in both years. Metolachlor plus flumetsulam plus clopyralid provided 90% or greater grass control over all experiments, with the exception of only 75% control at Dekalb in 1995 due to a heavy giant foxtail infestation. In comparison, flumetsulam plus clopyralid followed by postemergence applications of sethoxydim or nicosulfuron provided the same level of grass control as preemergence metolachlor, except at Dekalb in 1995 where control was 72% for both sethoxydim and nicosulfuron. Sequential applications of sethoxydim increased control of giant foxtail compared to a single sethoxydim application in 1995. Sethoxydim applied alone controlled giant foxtail 8% better than nicosulfuron at Urbana in 1996. Postemergence sethoxydim applied alone provided 87% or better control of giant foxtail. Sethoxydim performance was consistent when applied with flumetsulam plus clopyralid plus 2,4-D (NAF-73), halosulfuron plus dicamba, and bromoxynil. The efficacy of sethoxydim was reduced in combination with dicamba plus atrazine in three of the four trials, and bentazon plus atrazine as well as primisulfuron plus prosulfuron in all trials. Sethoxydim outperformed nicosulfuron in combinations with bromoxynil at Urbana. These studies indicate sethoxydim has excellent potential to be used in corn for postemergence control of giant foxtail.

Seedling emergence of broom snakeweed [Gutierrezia sarothrae (Pursh) Britt. & Rusby], threadleaf snakeweed [G. microcephala (DC.) Gray], common goldenweed [Isocoma coronopifolia (Gray) Greene], and false broomweed (Ericameria austrotexana M.C. Johnston) was studied in the glasshouse. Germination of these species is known to be light-stimulated. Seed of all four subshrubs germinated readily if placed on the surface or partially pressed into the soil. Emergence was reduced by covering seed with soil to a depth of less than 1 mm. Few seedlings emerged from a depth of 1 cm, and none emerged from a depth of 2 cm. Rate of emergence also decreased with increasing depth of placement. Soil texture had little effect on emergence. Rapid germination on the soil surface is consistent with other aspects of the regenerative strategy of common goldenweed and false broomweed, which do not depend upon a buried seed bank for regeneration. Seed burial probably provides a form of enforced dormancy in the small, long-lived seeds of the two snakeweed species.

Metribuzin [4-ammo-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] at 0.4 kg ai/ha controlled rape (Brassica hitra Moench. # SINAL) when applied 2.5 to 10 cm deep in a horizontal layer or in lines 1 to 4 cm apart. Trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) at 0.8 kg ai/ha did not control ‘Rox Orange’ forage sorghum [Sorghum bicolor (L.) Moench. # SORVU] satisfactorily when applied in a subsurface layer, in lines, or in vertical bands 1, 2, and 3 cm apart up to 10 cm deep. Applications of trifluralin at 1.1 kg ai/ha in vertical bands followed by 0.6 kg ai/ha mixed in the surface 2.5 cm controlled forage sorghum as well as or better than surface application followed by incorporation. The combined subsurface and surface trifluralin placement systems were effective for application depths up to 7.5 cm and band spacings up to 2 cm wide. The development of effective subsurface herbicide injection systems would make the use of herbicides requiring incorporation feasible in reduced tillage crop production systems.

Colorimetry, nephelometry, and chlorophyll assays of cultures of Chlamydomonas reinhardtii Dangeard, Chlorella pyrenoidosa Chick., and Scenedesmus quadricauda (Turp.) Bréb. were used as criteria for measuring algae growth. Among the four s-triazines studied, cyprazine appeared to be the most inhibitory to algae growth, followed by atrazine > simazine > cyanazine. Stimulatory effects of cyanazine, simazine, and cyprazine on chlorophyll content of C. reinhardtii and C. pyrenoidosa were also observed. Cyanazine was most stimulatory on both species but simazine also showed stimulation. Cyprazine was stimulatory only to C. reinhardtii at 0.22 μM concentration but apparently was inhibitory to C. pyrenoidosa at the same concentration. In one experiment, atrazine caused a slight stimulation in C. reinhardtii. Averaged over two consecutive experiments, however, atrazine was inhibitory. Chlorophyll content of the algae was found to be the best criterion for determining effect of the chemicals on algae growth. Continuous exposure of C. reinhardtii culture to the highest concentration of each of the four herbicides resulted in selection of algal lines having increased triazine tolerance.

Field studies evaluated response of soybean to Rhizoctonia foliar blight (RFB) disease in combination with varying densities of common cocklebur, hemp sesbania, or johnsongrass. Soybean plants at both V10 and R1 growth stages were not inoculated or inoculated with suspensions containing equal concentrations of Rhizoctonia solani AG-1 IA and IB mycelia. Intensity of RFB was rated weekly beginning at V1 soybean growth stage, and data were used to determine area under disease progress curves. Intensity of RFB was greater in 1993 than in 1994. When averaged across weed species and weed densities, soybean yield in 1993 was reduced 18% in plots inoculated with R. solani compared with those not inoculated. Intensity of RFB, however, did not differ between inoculated and noninoculated plots in 1994. Interactions between R. solani and weed density for RFB intensity and yield were not significant either year. Soybean yields in 1994, however, were reduced by hemp sesbania and johnsongrass in inoculated plots. Soybean maturity was delayed both years when hemp sesbania was present.

Established stands of alfalfa (Medicago sativa L.) at two field locations were treated at one date in the fall with pronamide [3,5-dichloro (N-1,1-dimethyl-2-propynil) benzamide] at 0.8 and 1.6 kg ai/ha and at two dates in the spring with sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} at 0.3 and 0.6 kg ai/ha for the control of quackgrass [Agropyron repens (L.) Beauv. # AGRRE]. Herbicide efficacy was compared by measuring botanical and chemical composition and yield of forage. Both chemicals suppressed quackgrass in first-cutting herbage. While sethoxydim at the higher rate was equivalent to pronamide for increasing the proportion of alfalfa in forage, pronamide was superior for increasing seasonal total yield. Late postemergence applications of sethoxydim were more effective for quackgrass regrowth control than earlier spring applications. Controlling quackgrass in late spring resulted in lower crude protein (CP) content in first-cutting forage than did controlling it in fall. Alfalfa competing with untreated quackgrass had a lower CP content than where quackgrass was controlled with herbicides. All herbicide treatments reduced the neutral-detergent fiber (NDF) of the herbage. As measured by the acid-detergent fiber (ADF) concentration of alfalfa, sethoxydim slightly retarded spring growth of the legume.

The effects of ethephon (2,chloroethyl-phosphonic acid), ancymidol [α-cyclopropyl-α-(4-methoxyphenyl)-4-pyrimidinemethanol], DPX1840 [3,3a-dihydro-2-(p-methoxyphenyl)-8H-pyrazolo(5,1-a)isoindol-8-one], Uni-P293 (2,3-dihydro-5-6-diphenyl-1,4-oxathiin), and morphactins and their interaction with GA (gibberellic acid) on the translocation of 2,4,5-T (2,4,5-trichlorophenoxacetic acid) in bean (Phaseolus vulgaris L. ‘Stringless Green-Pod’) seedlings were determined. The growth retardants and GA were either applied as foliar treatments or injected at the cotyledonary node with 2,4,5-T. Foliar pretreatment of bean seedlings with ethephon and ancymidol 2 days before 2,4,5-T treatment inhibited 2,4,5-T translocation to young shoots but did not affect basipetal translocation greatly. These effects were reversed by foliar application of GA 1 day before 2,4,5-T injection. Foliar pretreatment of bean seedlings with DPX 1840 2 days before 2,4,5-T treatment increased 2,4,5-T translocation to young shoots and inhibited basipetal translocation. The effects of DPX1840 were not reversed by GA treatment. When ancymidol, DPX 1840, and morphactins were injected into the stem tissue with 2,4,5-T the acropetal translocation of 2,4,5-T increased and basipetal translocation was decreased by DPX1840 and morphactins. These effects were not reversed by the simultaneous GA injection. Uni-P293 had little effect on 2,4,5-T translocation. Growth retardants other than Uni-P293 appear to inhibit basipetal 2,4,5-T translocation directly. Ethephon and ancymidol may have secondary effects on 2,4,5-T translocation that can be reversed by GA treatment.

This research compared seven field bindweed control treatments to a check in a 3-yr winter wheat-sorghum-fallow rotation. Treatments included 3 wk intervals of sweep tillage combined with one or two annual applications of 2,4-D (tillage and 2,4-D). Two other treatments were the same as tillage and 2,4-D, except dicamba or a mixture of picloram and 2,4-D were applied once in October after wheat harvest. A fourth treatment was identical to tillage and 2,4-D, except imazapyr was sprayed immediately after harvest of wheat. Also, three no-tillage systems using glyphosate and 2,4-D at monthly intervals were supplemented with either dicamba, picloram and 2,4-D, or imazapyr the same as in treatments involving tillage and 2,4-D. The check was sweep tilled every 6 wk. All treatments controlled field bindweed in one rotation of two fallow periods and two crops. After control was accomplished, wheat and sorghum yields were about twice the check. Using 1995 costs and returns, profit for an owner-operator for the two fallow periods and two crops was $123 ha−1 for tillage and 2,4-D, compared to $19 ha−1 for the check. Tillage and 2,4-D supplemented with picloram or imazapyr were almost as profitable as tillage and 2,4-D. Because of high herbicide cost and low yields, no-tillage treatments lost money. Profits with a 33:67 owner-tenant rental agreement were $105 and $21 ha−1, respectively, for owner and tenant using tillage and 2,4-D. With no field bindweed control practice, the tenant lost $33 ha−1 and the owner made $51 ha−1.

Prairie groundcherry [Physalis hederifolia (A. Gray) var. fendleri (A. Gray) Cronquist] is an invasive perennial weed with the potential to become a significant summer weed across 409 million hectares in Australia. Current management practices do not provide effective control of established populations. A better understanding of the seed biology is needed to effectively manage this weed. A series of field and laboratory studies were conducted to determine plant fecundity, soil seedbank longevity, and the factors that affect seed germination. Physalis hederifolia has the capacity to produce 66 to 86 berries plant−1, 51 to 74 seeds berry−1, and approximately 4,500 seeds plant−1, with the seeds potentially able to persist in the soil seedbank for 20 yr if buried in an intact dry berry pod. The bare-seed component of the soil seedbank can be virtually exhausted within 3 yr if cultivation is minimized to avoid burial of seed. Optimal temperature for germination is diurnal fluctuations of 15 C within the temperature range of 10 and 30 C. Increasing osmotic stress levels reduced the germination under all temperature regimes, with less than 6% germination occurring at −0.96 MPa. Physalis hederifolia seed germination was not significantly affected by substrate pH 4 to 10 or salt levels less than 160 mM, while the germination was significantly reduced at NaCl concentrations above 160 mM. These results suggest that P. hederifolia can adapt to a range of substrate conditions. Stopping seed set, avoiding grazing plants with viable seeds, and minimizing seed burial in the soil are some effective strategies to control this weed.

Silvex, [2-(2,4,5-trichlorophenoxy)propionic acid], impregnated (20% ae) on clay granules, applied at a rate as low as 20 lb/A ae gave excellent control of well-rooted alligatorweed [Alternanthera philoxeroides (Mart.) Grieb] growing in less than 18 inches of water. The 2-ethylhexyl ester of silvex was more effective than the potassium salt. Silvex was not effective on floating-mat alligatorweed or in water over 18 inches deep.

The atomization of jet streams from circular orifices, 279, 483, and 1016 microns in diameter, was measured under operating pressures less than 5 psi. The jet streams disintegrated into uniform large drops approximately twice the diameter of the jet orifice, and small drops making up less than 1% of the liquid volume from the small jet. About 80% of the spray from a jet discharging horizontally was deposited in a band 2 inches wide. The distribution pattern of horizontal jet streams positioned on a 2 inch spacing was improved by angling the jet streams 10–15° from the direction of travel.

Yellow nutsedge (Cyperus esculentus L.) is one of the most serious weeds in New York State. This weed has an extensive distribution in the state where it is a strong competitor with row crops especially corn, beans, and potatoes. Nutsedge is also an important weed problem in many other leading agricultural areas of the United States. The problem in all of these areas has increased recently, possibly due to a reduction of competition from other weeds which are being satisfactorily controlled by selective herbicides.

More than 80% of soybean [Glycine max (L.) Merr.] in Brazil is cultivated in no-till systems, and although cover crops benefit the soil, they may reduce the amount of residual herbicides reaching the soil, thereby decreasing herbicide efficacy. The objective of this study was to evaluate sulfentrazone applied alone, sequentially after glyphosate, and in a tank mixture with glyphosate before planting no-till soybean. Experiments were performed in two cover crop systems: (1) pearl millet [Pennisetum glaucum (L.) R. Br.] and (2) forage sorghum [Sorghum bicolor (L.) Moench ssp. bicolor]. The treatments tested were: glyphosate (720 g ae ha−1) at 20 d before sowing (DBS) followed by sulfentrazone (600 g ai ha−1) at 10 DBS; glyphosate + sulfentrazone (720 g ae ha−1 + 600 g ai ha−1) for cover crop desiccation at 10 DBS; and sulfentrazone alone at 10 DBS without a cover crop. The accumulation of straw was 31% greater using sorghum rather than pearl millet. In the sorghum system, the concentration of sulfentrazone at 0 to 10 cm was 57% less with sequential application and 92% less with the tank mixture compared with the treatment without cover crop straw at 1 d after application (DAA). The same occurred in the pearl millet system, where the reduction was 33% and 80% for the sequential application and tank mixture, respectively. The absence of a cover crop resulted in greater sulfentrazone concentrations in the top layer of the soil when compared with the sequential application or tank mixture. At 31 and 53 DAA, the concentration of sulfentrazone at 10 to 20 and 20 to 40 cm did not differ among treatments. Precipitation of 90 mm was enough to remove the herbicide from the cover crop straw at 31 DAA when using sequential application. An additional 90-mm precipitation was necessary to promote the same result when using the tank mixture.

The maleic hydrazide-30 treated plants increased in protein hydrolysate significantly over the controls, without having any growth. Therefore, this suggests that the synthesis of protein and metabolism of amino acids is not directly related to growth in tea (Camellia sinensis). The inhibitory effects may be due to the lack of synthesis of growth hormones responsible for cell enlargement, or may have a direct effect on the cell wall, reducing the cell plasticity. Hydrolysis with 6N HCl causes a significant destruction of amino acids.

In the past 10 years, phenomenal advances have been made in the regulation of plant growth by organic compounds including some now used as herbicides. The introduction of new chemicals, new weed-control techniques, such as pre-emergence treatment, and low gallonage application are among the most important recent developments in the use of organic compounds for weed control. It is estimated that losses caused by weeds on farms have now reached 5 billion dollars annually, and at present well over 30 million pounds alone of the phenoxy compounds, 2,4–dichloro, 2,4,5–trichloro-, and 2–methyl–4—chlorophenoxyacetic acids (2,4–D, 2,4,5–T and MCP) are being used for herbicidal purposes to help combat these losses (9). The most recent of these three compounds to appear on the market in this country as an active ingredient in herbicidal formulations is 2–methyl–4–chlorophenoxyacetic acid. The chief claim made for its use as a herbicide is that it is less injurious to certain grasses, cereal crops and legumes and more effective on certain weeds than 2,4–D. Fertig (4) concludes that MCP is slower in action and definitely less injurious to legumes, and Crafts (3) cites a number of investigators who have shown that MCP is more selective than 2,4–D, particularly where clover, flax and other crops having leaves hard to wet are concerned. High specificity of the compound is indicated by numerous reports in the literature; Robinson's (8), on the effectiveness of MCP in selective weed control, is one example. However, from recent recommendations (1), there appears to be some disagreement on the use of MCP, indicating need for further testing and experimentation with the compound and its derivatives. MCP as sold may contain up to 40% of impurities by weight, some of which, according to Hansen (6), may have toxic properties.