Puccinia coronata infection increased absorption of 14C-glyphosate in quackgrass 3 days after inoculation (DAI) when compared to 0,6,9, or 12 DAI. Days after inoculation had no effect on glyphosate translocation out of treated leaves until 9 to 12 DAI when 89% of the absorbed 14C-glyphosate was retained within the infected leaf. In contrast, only 43% was retained in leaves treated at 0 DAI. In other studies, 14C-glyphosate absorption increased linearly from 21 to 35% 12 to 96h after treatment (HAT). Differences between control and rust-infected plants were not significant. Sixty-three percent of absorbed 14C-glyphosate translocated out of control leaves by 96 HAT, while only 10% translocated out of rust-infected leaves. Additionally, 28 and 4% of the 14C absorbed was recovered from the rhizomes of control and rust-infected plants, respectively.

The theme for our meetings this year is “A Positive Concern for Society.” It is in this context that I will talk about “Weed Science in Perspective.” In doing so, we need to consider where we are, where we have been, and where we are going.

Experiments were conducted in controlled environment chambers to evaluate the effects of temperature and soil water content on the time of dissipation of commercial (CF) and starch encapsulated (SE) atrazine formulations to one-half the original concentration (T50). SE samples were also analyzed for the amount of atrazine remaining within the starch particles (percent encapsulation). The dissipation of CF atrazine was affected by changes in temperature and soil water content. SE atrazine dissipation was most influenced by changes in soil water content rather than temperature. Independent of soil water, there was no atrazine dissipation from any formulation at 15 C. The T50 for CF atrazine at 20% soil water content was 53.4 and 29.9 d for 25 and 35 C, respectively. At 20% soil water content, all SE treatments gave a T50 greater than 60 d. The percent starch encapsulation at 20% soil water content was greater than or equal to 55.8 and 30.4% for SE large and SE small, respectively. This high level of encapsulated atrazine accounts for the reduced SE dissipation observed at 20% soil water content. At 40% soil water content, the dissipation of CF and SE small atrazine were not different for either 25 or 35 C. Compared to the CF, the SE large formulation extended the T50 by 7.4 and 6.7 d at 25 and 35 C, respectively. At 40% soil water content, there was no encapsulated atrazine present in SE formulations 60 DAT.

During the course of investigation of the activity of some organic compounds selected for potential herbicidal effects (5), many candidates appeared to have activity equal to that of the standard 2,4–dichlorophenoxyacetic acid (2,4–D), while a few appeared to be more active. One of the latter was p–fluoro–o–toloxyacetic acid, which was first prepared by M. S. Newman (3).

Polyacrylamide electrophoresis and spectroscopic methods were used to characterize biotypes A and B itchgrass [Rottboellia exaltata L.f. # ROOEX] and their F2 progeny. Electrophoretic analyses of F2 progeny showed that differences between these two biotypes are multiallelic. Spectrophotometric data indicated differences between the photosynthetic apparatus of the two biotypes. These differences may reflect different abilities to adapt to varying light conditions and infer that these biotypes promote survival of the species by increasing the number of environmental nitches that R. exaltata can occupy.

When clay granules containing chlorpropham (isopropyl m-chlorocarbanilate) were applied to the surface of moist soil, the herbicide gradually moved to the atmosphere as a vapor and little entered the soil. Chlorpropham killed seedlings of field dodder (Cuascuta campestris Yunck.) and largeseed dodder (C. indecora Choisy) effectively whether it contacted them in the soil or in the air above the soil.

The persistence of picloram (4-amino-3,5,6-trichloropicolinic acid) was measured each spring over an 8-yr period following repeated annual applications at rates ranging from 0.020 to 0.070 kg/ha. Picloram residue levels were proportional to rate of application but averaged approximately 45% of the original levels when measured 12 months following application and declined to 10% 24 months after application ceased. Control of wild buckwheat (Polygonum convolvulus L.) was good with major population declines over the test period. Crop tolerance and yields were not affected at rates of 0.035 kg/ha or less.

The effects of thirteen plant growth regulators and herbicides on glucose absorption, metabolism, and incorporation in pea root tissues were studied. Both indoleacetic acid (IAA) and gibberellic acid (GA) caused no effects, while α-naphthalene-acetic acid (α-NAA) and β-naphthaleneacetic acid (β-NAA) caused an increase in catabolic and a decrease in anabolic processes, with the C-1 carbon undergoing the largest change. The absorption of glucose was also inhibited considerably by the synthetic auxins. The carbamates, isopropyl N-phenylcarbamate (IPC), n-Ethyl-N,N-di-n-propylthiolcarbamate (EPTC), and 3-(p-chlorophenyl)-1,1-dimethylurea (monuron) inhibited slightly the glucose absorption. All affected the catabolic process to a certain extent while only IPC caused a change in the anabolic process. Both 2,3,6-trichlorobenzoic acid (TBA) and 2,3,5-triiodobenzoic acid (TIBA) decreased glucose absorption and increased glucose-1-C14 catabolism. TIBA also affected the anabolic process. Other herbicides, 3-amino-1,2,4-triazole (amitrole), maleic hydrazide (MH), 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine), and 2,2-dichloropropionic acid (dalapon) caused varied degrees of inhibition to glucose absorption. Both simazine and dalapon increased C-1 catabolism and exerted no effect on the anabolic process. Only dalapon altered the catabolism of glucose-6-C14. Amitrole and MH decreased the over-all catabolic process with no effect on the pathway; both chemicals increased the anabolic process.

The question of direction and rate of movement of herbicidal chemicals in aquatic plants often arises in considering effective methods of chemical control for plants of this type. Results obtained from studies of solute movement within terrestrial plants are not directly applicable to totally submersed aquatic species for two reasons: a) A liquid medium, in which dissolved substances may be distributed uniformly, surrounds all parts of the aquatic plant, and b) Vascularization is minimal in leaf and stem tissues of submersed aquatics. Reports of experiments yielding quantitative data on translocation patterns in submersed aquatic plants are rare or nonexistent. It is probable that mechanical difficulties encountered in separating root systems from leaf or stem tissues of submersed plants have been of greater hindrance to translocation experiments with aquatic species than any other factors.

Vegetative propagules of sago pondweed (Potamogeton pectinatus L.) and American pondweed (P. nodosus Poir.) grown under a 14-hr photoperiod of light varying in chromatic composition produced plants with longer internodes and more extensive shoot and stolon development under red light than under blue. Pondweeds grown for 4 weeks under 25 to 400 ft-c of light made progressively more growth at the higher light intensities. Plant weight, branch number and stolon development increased while shoot length and shoot-root ratio decreased with increased light. Pondweeds grown under each of 5 light intensities at temperatures of 60, 70, or 80 F were treated with emulsified xylene or alkyl tolyl methyl trimethyl ammonium chloride. Pondweeds cultured at the higher light intensities and higher temperatures were progressively more injured. Injury from treatment with either herbicide increased with age and plant maturity from early vegetative to flower-bud stage. Equivalent injury was produced on plants of equivalent maturity regardless of chronological age. Pondweeds cultured under 400 ft-c of light and a 14-hr photoperiod required approximately 900 degree-days over a 49 F threshold to reach flower-bud stage.

Annual applications for 4 years of 2,6-dichlorobenzonitrile (dichlobenil), N,N-dimethyl-2,2-diphenylacetamide (diphenamid), 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine), 3-amino-2,5-dichlorobenzoic acid (chloramben), and 1,1′-dimethyl-4,4′-bipyridinium ion (paraquat) to a red raspberry (Rubus sp. ‘Newburgh’) planting had no direct deleterious effect upon the raspberry plants. Dichlobenil, simazine, and paraquat gave excellent weed control. Weed competition in control plots seriously reduced yields. Shoot development was delayed when dichlobenil was applied near the time of normal bud break.

The emergence of Sorghum bicolor seedlings and the dormancy status and survival of S. bicolor seeds buried in soil in the midwestern United States were studied from 1992 to 1995. Possible causes of seed mortality were also investigated. Emergence of seedlings from seeds buried in November averaged less than 2%, compared with 28% from seeds buried in March. Seeds showed little ability to survive winter, with more than 80% dying between November and March and virtually none surviving a second winter. Many seeds exhibited signs of cold damage. Further evidence of the effect of cold was the decreased mortality of seeds protected somewhat from the cold. The decline in the viability of seeds was modeled well by negative exponential curves with an exponent of between 0.011 and 0.016.

Individual herbicides and all double combinations of imazaquin, imazethapyr, and imazapyr were applied alone and in combination to the foliage of pitted morningglory plants in order to evaluate potential influences on translocation. Unlabeled imazethapyr at 5.62 μg plant−1 stimulated basipetal translocation of both 14C-imazaquin and 14C–imazapyr. Unlabeled imazaquin at 7.49 μg plant−1 also increased basipetal translocation of 14C–imazethapyr but did not influence 14C–imazapyr translocation. No combination affected the amount of 14C herbicide remaining in treated leaves or moving into foliage above treated leaves. Unlabeled imazapyr at 0.11 μg plant−1 did not affect movement of either imazaquin or imazethapyr.

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.

In preemergence application of six different substituted urea herbicides on coriander (Coriandrum sativum L.) and tomato (Lycopersicum esculentum Mill.), the monohalogenated compounds were more effective in the destruction of the plants than their dihalogenated counterparts. The relative difference in effectiveness was much greater in the resistant coriander which appears to take up less dihalogenated than monohalogenated herbicide. In postemergence application, the dihalogenated herbicides generally were slightly more toxic than their monohalogenated counterparts.

The Beatitudes could well be extended to bless those who continue to pursue learning aggressively throughout their life, for surely such individuals shall be confronted with challenge and their days shall be full of wonderment and accomplishment and self-satisfaction. As I reflect on this business of learning, it is apparent that a great deal of it takes place at the subconscious level. Throughout all of my undergraduate and graduate student days and ever since through affiliation with knowledgeable associates, the concept of professionalism seems to have been taking shape for me as an individual. Perhaps it is well at this juncture in the life of WSSA to consider what professionalism means for the discipline of weed science.

Nemaha oats and 3-amino-2,5-dichlorobenzoic acid (amiben) were effective in reducing weed growth during sweetclover establishment. Hubam and Madrid sweetclover, as well as Nemaha oats, were tolerant of amiben rates necessary for annual weed control. Second-year Madrid sweetclover hay yields were increased from amiben applications the previous year.

Since 2,4–D became recognized as a weed killer, thousands of experimental plots have been sprayed with this and numerous other chemicals. The various weed conferences have prescribed uniform experiments with uniform rates and dates of application, but there has been no uniform method of application. In order to apply the minute quantities of chemicals needed on small plots, it is absolutely essential that a constant pressure and speed be maintained and that uniform coverage of the entire plot be obtained.

The effects of tobacco thrips (Frankliniella fusca Hinds) control and herbicides on peanut (Arachis hypogaea L. ‘Florigiant’) canopy development and competition with large crabgrass [Digitaria sanguinalis (L.) Scop. # DIGSA] were examined in field experiments during 1983 and 1984. Greater early-season peanut canopy development generally occurred when tobacco thrips were controlled with aldicarb [2-methyl-2-(methylthio) propionaldehyde-O-(methylcarbamoyl)oxime]. Tobacco thrips control did not affect large crabgrass dry weights or peanut seed yields with no herbicide, alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide], vernolate (S-propyl dipropylcarbamothioate) + benefin [N-butyl-N-ethyl-2,6-dinitro-4-(trifluoromethyl)benzenamine] + alachlor, and handweeding + sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio) propyl]-3-hydroxy-2-cyclohexen-1-one}. Averaged across weed control levels, large crabgrass dry weights with and without aldicarb were 320 and 310 g/m2 in 1983, and 260 and 250 g/m2 in 1984, respectively. Peanut seed yields with and without aldicarb were 1550 and 1630 kg/ha in 1983, and 2870 and 2920 kg/ha in 1984, respectively.

Eight triazolopyrimidine sulfonanilides were tested for metabolic stability in a number of crop and weed species. These data, along with in vitro determinations of activity (I50) against acetolactate synthase, successfully described the in vivo activity of these compounds in a two-parameter model. Whole plant activity increased with increasing compound stability and decreasing I50 (r2 =.78, N = 36). The difficulty in obtaining metabolic stability data during a structure optimization program prompted a study with substituent parameters in models of in vivo activity. Models describing whole plant activity in jimsonweed were developed using a series of 5-methyl triazolopyrimidine sulfonanilides that differed only in ortho and meta substituents on the aniline ring. The I50 term and clogP were most important to jimsonweed activity. Hence, in vitro activity (I50) may be a useful component of whole plant structure activity models to aid in identification of barriers to in vivo performance.