Vinasse, a liquid fermentation residual of bio-ethanol production that also contains solid particles in suspension, is commonly used as a soil amendment. Previous studies reported vinasse reduced seed germination and seedling establishment, suggesting herbicidal activity. Laboratory experiments were conducted to determine whether vinasse herbicidal activity is present in the liquid or solid phase, and whether it affects plants during seed early germination (i.e., imbibition), late germination (i.e., embryo growth and radicle protrusion), or seedling growth. Most of the herbicidal activity was associated with the liquid phase, and for most species, seed viability was predominantly affected after the imbibition phase. Susceptibility to vinasse was species dependent. Lettuce (Lactuca sativa L.) germination was <8% when seeds were imbibed and germinated in vinasse solutions or imbibed in water and germinated in vinasse. Conversely, imbibing lettuce seeds in vinasse solutions and germinating them in water did not change their germination in comparison with seeds imbibed and germinated in water (>80% germination). Wheat (Triticum aestivum L.) and sicklepod [Senna obtusifolia (L.) H. S. Irwin & Barneby] germination decreased 10% and 35% when seeds were imbibed and germinated in vinasse, respectively, while Palmer amaranth (Amaranthus palmeri S. Watson) and southern crabgrass [Digitaria ciliaris (Retz.) Koeler] germination decreased >90%. All evaluated species reduced radicle growth as vinasse concentration increased. Filtered liquid vinasse with reduced concentration of salt and ionic compounds inhibited radicle growth similarly to unfiltered vinasse, indicating that the herbicidal activity was not due to osmotic effects and was likely present in the organic liquid phase. Amaranthus palmeri, S. obtusifolia, and D. ciliaris increased the proportion of dormant seed more than 2-fold when they were imbibed or imbibed and germinated in vinasse solutions. Vinasse might be useful for weed management to reduce germinable weed seedbanks by increasing seedling mortality and seed dormancy either by properly timing of its application as a soil amendment or by purifying herbicidal compounds and using them directly for weed control.

I am honored to meet here today with this distinguished group of scientists, engineers, educators and businessmen. I have looked forward to this conference as an opportunity particularly to discuss the problem of chemicals in our environment, a matter which concerns us all deeply … and to describe some of the steps we are taking in the Department in this regard. I also want to discuss our activities as they apply to the broader context of the responsibilities of science and education today in agriculture.

A 2-year experiment was conducted to determine the time interval between flowering and viable seed production in common milkweed (Asclepias syriaca L.). A high percentage of seeds harvested 6 weeks after flowering germinated. Seeds harvested 6 and 7 weeks after flowering resulted in seedlings with significantly shorter radicles and hypocotyls than seeds harvested 8 weeks after flowering. There was a close association between seed weight and radicle and hypocotyl length. Common milkweed produced viable seeds 5 to 6 weeks after flowering.

The preemergence efficacy of soil surface applications of a Phomopsis convolvulus granular formulation to control field bindweed seedlings was compared with its efficacy when inoculum granules were incorporated in soil. In addition, the effect of different doses of soil-applied granules was also determined. Under controlled environment conditions, incorporation of the fungal granules resulted in aboveground biomass reductions between 88 and 96%, with no significant differences observed between incorporation depths of 1.5 and 3 cm. Granule applications on the soil surface were less effective, reducing aboveground biomass 40 to 83%. In a parallel field experiment conducted over two growing seasons, however, surface applications of inoculum granules resulted in greater weed control compared with soil incorporation of the granules. In spring and summer trials conducted in 1996, surface applications resulted in a 93 and 100% aboveground biomass reduction, respectively, whereas incorporated granules reduced biomass 62 and 97%. Similar trends were observed in 1997. Different soil-applied doses of P. convolvulus did not affect the level of weed control under both controlled environment and field conditions. In 1995 and 1996 field trials, all rates used (30, 20, and 10 g 0.25m−2plot) resulted in substantial (90 to 100%) field bindweed aboveground biomass reductions. Findings in this study indicate that under field conditions, preemergence applications of the bioherbicide P. convolvulus on the soil surface provide effective control of field bindweed.

Purple nutsedge (Cyperus rotundus L.) plants from tubers uniformly planted in fumigated soil were treated with 2,4-D [(2,4-dichlorophenoxy)acetic acid], paraquat (1,1′-dimethyl-4,4′-bipyridinium ion), or dinoseb (2-sec-butyl-4-6-dinitrophenol). Repeated applications were made as required on the 1972 and 1973 plantings for one growing season. Emerged plants and their parent tubers were killed by four (1972) or five (1973) applications of paraquat. Three applications of 2,4-D were required for control in 1972. In 1973, a single treatment of 2,4-D afforded almost complete control. Three applications of dinoseb were required in 1972, but five were required in 1973.

The feasibility of using the spurge hawkmoth (Hyles euphorbiae L., Lepidoptera: Sphingidae), as a biological control agent on leafy spurge (Euphorbia esula L.) was evaluated. Studies relating adult hawkmoth emergence from the pupal stage and spring growth of leafy spurge plants showed that the plants would provide food and oviposition sites for the insect. Two generations of the insect may occur each year. Winter temperatures at approximately 2.5 cm below the soil surface or in the litter would result in some mortality of hawkmoth pupae. Pupal release programs indicated that protection from insect and rodent predators was necessary for adult emergence to occur. Predator determination using 32P indicated two specimens of Calosoma calidum Fab. and two specimens of Formica subsericea Say as possible predators. Predator determination using pitfall traps showed that several species listed by Canadian researchers as predators were present in leafy spurge stands in Nebraska. At this time it appears the spurge hawkmoth will not become a valuable biological control agent for leafy spurge in Nebraska.

The goal of this research was to determine if differing levels of tolerance to AC 263,222 exist in soybean. 14C-AC 263,222 was foliar-applied to ‘Coker 6955,’ ‘Hartz 6686,’ ‘Hutcheson,’ ‘9581 Pioneer,’ ‘9681 Pioneer,’ and ‘RA 606’ soybean cultivars. Differential absorption of 14C-AC 263,222 was evident among cultivars 48 and 96 h after application. Movement out of the treated leaf was both acropetal and basipetal, indicating xylem and phloem mobility. Although absorption and translocation differences occurred among cultivars, these differences do not explain the differential response of soybean cultivars to AC 263,222. Metabolism of 14C-AC 263,222 differed greatly among cultivars and increased with time. Ninety-six h after application, 9581 Pioneer metabolized 66% of the absorbed 14C-AC 263,222, compared to RA 606, which metabolized only 41%. The large differences in metabolism that occurred 48 and 96 h after application suggest that metabolism is responsible for the differential response of soybean cultivars to AC 263,222.

Ethofumesate [(±)-2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate] was evaluated in field experiments at rates from 0.6 to 4.5 kg/ha for control of volunteer wheat (Triticum aestivum L. ‘Hyslop’, ‘Stephens’) in fall-planted perennial ryegrass (Lolium perenne L. ‘Cropper’, ‘Pelo’, ‘Pennfine’, ‘Omega’). Ethofumesate applied at 1.7 kg/ha or more in mid-November to wheat in the one-to three-leaf stage eliminated the wheat. Wheat was not eliminated when ethofumesate was applied preemergence soon after planting or when applied at the end of November to wheat in the four-leaf to four-tiller stage. In four experiments in which wheat was present, ethofumesate significantly increased perennial ryegrass seed production. In one experiment in which wheat was not present, ethofumesate did not affect perennial ryegrass seed production. Ethofumesate applied in the fall at rates to 4.5 kg/ha to newly-seeded perennial ryegrass or to well-established bentgrass (Agrostis tenuis Sibth. ‘Highland’), Kentucky bluegrass (Poa pratensis L. ‘Newport’), and Italian ryegrass (Lolium multiflorum Lam.) did not adversely affect germination of the following seed crop.

Bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-(4) 3H-one 2,2-dioxide], cyperquat (1-methyl-4-phenylpyridinium), and perfluidone {1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl)phenyl] methanesulfonamide} were evaluated for their potential use as postemergence herbicides for selective yellow nutsedge (Cyperus esculentus L.) control in Kentucky bluegrass (Poa pratensis L.) in field studies. High rates of these herbicides as single or split applications were effective and only slightly reduced verdure of Kentucky bluegrass, indicating excellent selectivity. In greenhouse studies perfluidone exhibited growth retardant properties. Shoot dry weight production was inhibited and root dry weight of treated plants was markedly reduced. These two factors are undesirable features for commercial sod production.

MSMA (monosodium methanearsonate) and DSMA (disodium methanearsonate) killed 27 to 90% of the broomsedge (Andropogon virginicus L.) plants when applied at 1.1 to 6.7 kg/ha in July. These rates did not reduce yields of smooth bromegrass (Bromus inermis Leyss.) or affect the density of Kentucky bluegrass (Poa pratensis L.) growing in association with the broomsedge.

Many problems in weed science may be solved by utilizing immunochemical techniques, although these techniques are currently underutilized by weed scientists. In this review, we describe some of the methods of greatest use to weed scientists. Antibodies may be raised against proteins, such as the targets of herbicide action or against the herbicide itself which can be linked to a larger molecule so that antibodies are elicited. Once specific antibodies are obtained, several techniques may be performed utilizing the binding phenomena of antibody-antigen interactions. Immunofluorescence and immunogold electron microscopy are utilized to obtain tissue and subcellular distributions of the protein or herbicide of interest. Quantitation of either protein or herbicide in a given sample may be performed by ELISA or “slot” and “dot” blotting. These protocols are less costly, more sensitive, and much less labor-intensive than most analytical methods. Molecular mass or charge alterations may be determined by electrophoresis and subsequent immunoblotting. With the increased exposure to immunological techniques by weed scientists and their potential utility, we predict that many more weed science problems will be addressed using these protocols.

Effects of the alkanolamine salt of (2,4-dichlorophenoxy) acetic acid (2,4-D) and sodium salt of 4-hydroxy-3,5-diiodobenzonitrile (ioxynil) upon seedlings of Chewings fescue (Festuca rubra var. commutata Gaud.), Park bluegrass (Poa pratensis L.), and Highland bentgrass (Agrostis tenuis Sibth.) were evaluated in growth room and field studies. In the former, injury to Park bluegrass from both 1 and 3 lb/A applications of 2,4-D was severe with pronounced but less marked effects on fescue and bentgrass. Results were similar from applications shortly after emergence and after clipping the grass. Negligible injury was caused by 1 lb/A of ioxynil. In the field, ioxynil gave better weed control than 2,4-D when applied at a seedling height of 1 inch. No injury was caused by ioxynil. Although 2,4-D reduced yields from early clippings, there was marked recovery, even at 3 lb/A. No treatments significantly affected plant stand.

Uptake and movement of various herbicides and auxins by bean (Phaseolus vulgaris L.) petiole sections were studied. Isopropyl m-chlorocarbanilate (chlorpropham) was the most mobile of the compunds studied, followed in order of decreasing mobility by: indole-3-acetic acid (IAA), 3-amino-s-triazole (amitrole), (2,4-dichlorophenoxy)acetic acid (2,4-D), 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron), and 3-amino-2,5-dichlorobenzoic acid (amiben). Amiben immobilization may have been due to glucoside formation in the tissues. IAA was rapidly transported through basipetally but not acropetally oriented tissue. Tissue orientation had little effect on the movement of the other compounds. Mobility of the compounds studied, in general, appears to be a function of the amount of uncomplexed parent chemical. Retention is likely the result of conjugation with products in the cells or of physical binding in the cells.

Although similar in mode of action, 1,2-dihydroxybenzene (catechol) and 1,1′-dimethyl-4,4′bipyridinium ion (paraquat) at different levels were required to kill plants. Both chemicals were fast-acting, they both required light to be active, and herbicides that inhibit photosynthesis protected the plants temporarily against the action of both compounds. Paraquat and catechol had additive effects on black nightshade (Solanum nigrum L.) but not on redroot pigweed (Amaranthus retroflexus L.). Catechol protected redroot pigweed against the action of paraquat.

Suspension cultures of proso millet cells were treated with haloxyfop at different phases of growth. Treatment of 1-d cultures with 1 μM haloxyfop completely inhibited growth within 48 h. In contrast, 1 mM haloxyfop was required to elicit a similar response in 4-, 7-, or 10-d cultures. Calculated IC50 values indicated a 300-fold decrease in haloxyfop sensitivity during the period from 1 to 4 d. The observed changes in sensitivity to haloxyfop could not be attributed to changes in cell concentration during culture growth. In both 1-d and 4-d cultures, an initial rapid uptake of radiolabel was followed by a slow loss of radiolabel from cells. Almost all radioactivity extracted from 1-d and 4-d cells was present as the parent acid. Several radiolabeled compounds in addition to the parent acid were present in media. No major differences in the amounts of these materials were found between 1-d and 4-d media. Our results indicate that a special aspect of metabolism expressed during cell division is particularly sensitive to the herbicide.

Weed management for nursery ornamental plants requires several applications of preemergence herbicides to control recurring weed emergence and to counter chemical dissipation and leaching losses. Herbicide losses from plant containers in runoff water may pose risks to surface and groundwater supplies. Sphagnum peat is a frequently used rooting medium. Limited information exists on the fate of herbicides applied to peat. The leaching of two commonly used chemicals in Europe by the containerized ornamental plant industry, isoxaben and BAS 479 14H, was measured. Herbicides were applied to 1-yr-old conifers (Juniperus communis, cv. Repanda [common juniper]) grown in pots containing sphagnum peat. The isoxaben-treated pots were placed on 1- by 1-m lysimeters that were buried in the center of replicate field plots. Pots were also placed in subirrigated sandbeds to determine herbicide dissipation and movement in irrigation water. With overhead irrigation, isoxaben had a half-life of 2 mo in the 0- to 5-cm depth of the peat container. More than 96% of applied isoxaben was recovered in the 0- to 5-cm depth. Less than 4% of the amount applied was found in the 5- to 10-cm depth, and none was detected in the 10- to 15-cm depth. No isoxaben residues were detected in water percolating through the field lysimeters. In subirrigated sandbeds, no isoxaben was detected in the water rising by capillary tension. Most of the applied isoxaben was found in the 0- to 5-cm layer of the peat container, where its half-life was also 2 mo. Similar results were observed in containers treated with BAS 479 14H, which had a half-life of 1.2 mo. The high organic matter content of the peat medium strongly sorbed both isoxaben and BAS 479 14H, and these herbicides remained primarily in the near-surface zone of the peat containers. No significant herbicide leaching or loss from the containers was found when subirrigated or irrigated by sprinkler.

Photosynthetic productivity parameters were determined for mayweed chamomile, a troublesome annual weed of the cropping systems in the Pacific Northwest. At a photosynthetic photon flux density of 1800 μE m−2 s–1, maximum net photosynthetic rate of greenhouse-grown plants was 35 mg CO2 dm−2 h–1 and maximum transpiration rate was 6.7 μg H2O cm−2 s–1. Dark respiration rate was 1.4 mg CO2 dm−2 h–1 and the light compensation point was 17.5 μE m−2 s–1. Carbon dioxide compensation point increased from 25 ppm at 15 C to 43 ppm at 30 C. At saturating photosynthetic photon flux densities, optimum leaf temperature for net photosynthesis was about 25 C. Maximum net photosynthesis of leaves of field-grown plants averaged 15.8 mg CO2 dm−2 h–1. After a 24-h exposure to 0.075 kg ha–1 metribuzin, maximum net photosynthesis and transpiration were reduced 85 and 40%, respectively. Soil water deficits reduced maximum net photosynthesis about 50%.