The herbicide S-ethyl hexahydro-1H-azepine-1-carbothioate [molinate] at 0, 3, and 6 lb/A was applied to drill-seeded rice [Oryza sativa L.] into the irrigation water at 8, 13, and 20 days after rice and weed emergence; the plots remained flooded for 2, 7, or 12 days. Three lb/A applied when weeds had 1 to 6 leaves and rice had 2 to 8 leaves controlled barnyardgrass [Echinochloa crusgalli (L.) Beauv.] and broadleaf signalgrass [Brachiaria platyphylla (Griseb.) Nash] and did not injure rice when the water remained for 7 or 12 days. Weed control and yield of rice were reduced when the irrigation water was held for only 2 days. When the weeds were tillering, molinate controlled barnyardgrass better than it controlled broadleaf signalgrass. Molinate at 0, 3, and 6 lb/A was applied to drill-seeded rice into the irrigation water 1 week after rice and weed emergence; 7 days later the water was either left on the plots or was drained for 5, 10, 20, or 29 days. Three lb/A usually prevented reinfestations of barnyardgrass when plots were drained for 5, 10, or 20 days. Barnyardgrass reinfested rice drained for 29 days and reduced yields.

For 3 yr, fluridone {1-methyl-3-phenyl-5-[3-(trifluoromethyl)phenyl]-4(1H)-pyridinone} at 0.1, 0.2, and 0.3 kg/ha, was applied with or without 0.6 kg/ha of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) before the preplanting irrigation for cotton (Gossypium hirsutum L.). Without trifluralin, fluridone at 0.1 kg/ha controlled less than 60% of annual grasses or redroot pigweed (Amaranthus retroflexus L.), but the 0.3-kg/ha rate controlled 90%. With trifluralin, fluridone at all rates controlled 98% of these weeds. Fluridone alone controlled 85% or more of black nightshade (Solanum nigrum L.). Fluridone did not alter cotton stand or yield. Fluridone residues 8 months after treatment reduced growth of several crops and weeds by 75% or more.

Using nutrient culture techniques, it was determined that a 14-day exposure to metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] concentrations in the range of 10-6 M reduced lengths and weights of seedling sweet corn (Zea mays saccharata L. ‘NK-199′) shoots and roots by 30 to 50%. With the exception of root weight, intensity of inhibition was proportional to day length. Reductions in accumulation of Ca, Mg, K, and P accompanied decreases in sweet corn growth. A 4-day exposure of sweet corn to 2.8 and 5.6 × 10-6 M metolachlor had no significant effect on growth and nutrient accumulation when treatments were followed by a 9-day incubation in metolachlor-free nutrient solution.

A modified analytical procedure involving gas-liquid chromatography was used to investigate the relative amounts of 2,4-D [(2,4-dichlorophenoxy)acetic acid] and two of its amino acid conjugate metabolites, 2,4-D-Asp [(2,4-dichlorophenoxy)acetylaspartic acid] and 2,4-D-Glu [(2,4-dichlorophenoxy)acetylglutamic acid], in soybean [Glycine max (L.) Merr. var. Amsoy] plants, soybean callus tissue and red oak (Quercus rubra L.) plants at 2, 4, and 10 days after application of either 2,4-D, its ester, or its salts. 2,4-D-Asp and 2,4-D-Glu were found as major metabolites in all soybean tissues analyzed and their amounts varied depending upon the days following treatment, the formulation of treatment, and the plant substrate (0.03 to 57 ppm for 2,4-D-Asp and 0.05 to 75 ppm for 2,4-D-Glu). The amount of amino acid conjugates peaked at 2 days after treatment of callus tissue and 4 days after treatment of soybean plants. Much higher amounts of these amino acid conjugates were obtained from soybean plants treated with the propylene glycol butyl ether ester of 2,4-D than plants treated with amine salts of 2,4-D. No amino acid conjugates were observed with red oak plants.

The establishment of plants in an ecosystem is limited by the availability of seeds and the availability of suitable sites for establishment. Describing plant population dynamics through the relative strength of seed and establishment limitation is an important concept in the study of natural ecosystems. To date, it is unclear whether this concept can be applied to describe populations of annual weeds in agricultural fields. Using a recruitment function, we show that limitation parameters prove valuable in describing seedling recruitment in weed populations. We conducted a seed addition experiment in three cornfields (Zea mays L.) and recorded seedling recruitment in populations of the economically important weed barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.]. Seed predation, competition with other weeds, and seed burial were prevented. We estimated the strength of seed and establishment limitation in the population with two parameters: n, which is the number of microsites, and b, which is the suitability of those sites to support a seedling. We further estimated the relative proportions of density-dependent and density-independent establishment limitation in the seedling population. Recruitment rates of E. crus-galli ranged from 31% to 36% across all evaluated seed densities and fields, which is high compared with results from other seed addition studies. Two of the three monitored populations were predominantly establishment limited at the highest evaluated seed density of 2,400 added seeds m−2. Further knowledge about the relative strength of limitations in other weed populations will provide important information on how effective different weed management strategies can be.

The analysis of allelopathic bioassay data commonly encounters two problems: one is the small number of biological replicates and the other is that the parameters used to infer allelopathic effects such as percentage and average time of seed germination are analyzed individually, and consequently, information on the global effects resulting from the cumulative effects of the tested agent (e.g., leaves extract) may be missed. Therefore, we propose an index to analyze several parameters altogether so as to have a better view of the global influence of a donor plant on a receptor, whose interference is more likely to be detected. The global effect index can help to detect allelopathic interferences of one plant on another, allowing for a more accurate interpretation of the data in the actual biological setting.

Highbush blueberries [Vaccinium australe (Small), var. Colville] grown on a Leon sand at Chatsworth, New Jersey were treated with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) and 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) each spring or each spring and fall from 1960 through 1966. The weed control obtained with diuron generally improved with continued use. At rates of simazine sufficient to achieve satisfactory control, the degree of weed control increased for the first 3 years and decreased the last 3 years. Diuron and simazine at rates sufficient to provide satisfactory weed control did not reduce the productivity of the blueberry plant. Palatability evaluations of off-flavor and sweetness of frozen blueberries, and objective measurements of pH and soluble solids, indicated that the diuron and simazine treatments did not affect any of these quality factors.

Gamma radiation of 3 megarads was applied to undiluted commercial formulations and aqueous solutions of 3-(3,4 dichlorophenyl)-1,1-dimethylurea (diuron), 1,1-dimethyl-(3-a,a,a-trifluoro-m-tolyl)-urea fluometuron), N,N-dimethyl-2,2-diphenylacetamide (diphenamid), 2,4-bis (isopropylamino)-6-(methylthio)-s-triazine (prometryne), dimethyl tetrachloroterephthalate (DCPA), a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) and sodium chlorate. The effect of radiation on herbicidal activity was assessed with bioassays. Radiation did not affect the bioactivity of undiluted or 50% solutions of any of the tested herbicides but decreased appreciably the activity of 100-ppm solutions of fluometuron, diphenamid, and prometryne. Diluted 100 and 10-ppm solutions of trifluralin lost part of their activity during storage in plastic containers and, in addition, following irradiation. It was not clear whether the decrease in activity observed in the 100-ppm solution of diuron was due to irradiation or to storage. No reduction in bioactivity was produced following irradiation of 100 and 10-ppm solutions of DCPA or 1% and 10% solutions of sodium chlorate.

Small broomrape is a federally listed noxious weed that was first identified in Oregon in 1923. Between 1923 and 1997, there were only six reports of the species in Oregon. Small broomrape is a holoparasitic weed that attaches to the root of its host and can lead to crop failure depending on the level of infestation. Small broomrape was identified in a red clover field in Oregon in 1998. In 2000 and 2001, the Oregon Department of Agriculture surveyed red and white clover fields in Oregon for the presence of small broomrape; 15 infested fields were identified in 2000 and 22 in 2001. The source of the small broomrape seed was not identified although there was speculation that small broomrape seed may have been contaminated clover seed stock. In 2000, a quarantine was established for small broomrape in red clover seed. Research identified effective, easy to implement management strategies for small broomrape including the use of false host crops and imazamox. In 2003, the ODA amended the quarantine to eliminate the mandatory seed sampling and testing and the requirement of reporting infested fields and seed lots. In 2011, there are still populations of small broomrape present in red clover fields in Oregon.

Growth-chamber studies were conducted to determine the effect of p-chlorophenyl-N-methylcarbamate (PPG-124) and 1-naphthyl N-methyl carbamate (carbaryl) on the response of safflower (Carthamus tinctorius L. ‘Gila’) and common buckwheat (Fagopyrum esculentum Moench.) to isopropyl m-chlorocarbanilate (chlorpropham). Addition of PPG-124 or carbaryl did not increase the sensitivity of safflower, a resistant species, to chlorpropham and affected buckwheat, a susceptible species, only at the lowest dosage level.

Modifications were investigated to improve shelf-life or long-term survival upon storage of an extruded Oryza sativa L. (rice) flour : gluten : clay: oil formulation (C7) of a mycoherbicide, Fusarium oxysporum Schlechtend: Fr. f. sp. erythroxyli strain EN4, that causes vascular wilt in Erythroxylum coca var. coca (coca). Fermentor-produced biomass, which contained abundant desiccation-resistant chlamydospores, was incorporated into various adaptations of C7 and stored at room temperature (22 to 25 C) under moderately high (50 to 60%) and low (0 to 5%) relative humidities (RHs). The effect of RH on shelf-life was not significant up to 4 mo of storage, while the presence of oil, added to improve its extrusion, reduced viability significantly. Addition of Gossypium hirsutum L. (cotton) embryo flour or complete elimination of oil from the formulation improved shelf-life from 3 mo to > 12 mo. Shelf-life was further improved by removing the binding agent gluten in the formulation and replacing it with autoclaved O. sativa flour. Ability of the formulations to produce secondary propagules, tested on 1% water agar, indicated that, while adding oil had no effect, G. hirsutum embryo flour increased desiccation-resistant chlamydospore counts but lowered macroconidial counts. Autoclaved rice flour (MR) significantly improved both macroconidial and microconidial counts without affecting chlamydospore counts. None of the formulations affected the total viable propagule counts. When compared with the original formulation (C7), the modification (MRRP7), with MR, G. hirsutum embryo flour, and without oil, was found to have improved shelf-life at higher temperature and RHs and enhanced potential for secondary chlamydospore formation. These characteristics are important for survival of the formulated F. oxysporum under less expensive storage conditions and, once applied, for survival in the soil.

The future of weed science, and indeed of all of modern agricultural science and technology, is in jeopardy today because the public does not clearly understand their importance. As a result, decisions may be made and actions taken that can, and will if continued, most certainly destroy our complex and highly productive agricultural systems where one worker annually provides food for more than 46 people. We can improve prospects for the future by effective action.

Seedlings of corn (Zea mays L., var. GT-112 RfRf and GT-112, resistant and susceptible, respectively) to 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) were grown 48 hr in sterile Hoagland's solution containing 14C-ethyl-labeled atrazine. More incorporation of the 14C-ethyl side-chain into free amino acids was found in the roots and shoots of GT-112 RfRf than GT-112, based on radioactivity. More radioactivity was found in roots of susceptible plants than in resistant plants; however, the trend was reversed in the shoots.

Efficacy of glyphosate on bulbous oatgrass, a creeping perennial grass, was investigated in greenhouse and growth chamber studies. Glyphosate at 1.2 and 2.5 kg ae ha−1 significantly reduced corm formation and corm viability. Glyphosate controlled bulbous oatgrass when applied at the 4- to 5- or 6- to 7-leaf stage. With 2.5 kg ha−1, a 24-h period between glyphosate application and removal of the shoots was sufficient to cause maximum reduction in regrowth. Total amount of 14C translocated out of leaves treated with radiolabeled glyphosate (1.0 kg ha−1 total glyphosate) did not differ among growth stages, but more 14C accumulated in the dormant corms when glyphosate was applied at the 2- to 3-leaf stage than at the 4- to 5- or 6- to 7-leaf stages. Lack of correlation between maximum plant injury and glyphosate accumulation in corms is not understood but may be related to differences in application method in the two studies.

Several herbicides were evaluated for control of western false hellebore (Veratrum californicum Durand). The dimethylamine salt and propylene glycol butyl ether esters of (2,4-dichlorophenoxy)acetic acid (2,4-D), potassium salt of 2-[(4-chloro-o-tolyl)oxy]propionic acid (mecoprop), and the butoxy ethanol ester of 2-(2,4,5-trichlorophenoxy)propionic acid (silvex) controlled 95 to 99% of the plants when applied at 2 lb/A followed by 2 lb/A of the dimethylamine salt of 2,4-D the second year. Optimum control was achieved when plants were treated after the last leaf had expanded and before flower bud initiation.

Field studies were conducted to determine suitability of flurtamone alone and in tank mixture with ethalfluralin for selective control of weeds in safflower. Flurtamone at 0.6 to 0.9 kg ha−1 controlled field pennycress, kochia, and Russian thistle. Flurtamone and ethalfluralin were compatible in tank mixture and provided comparable or superior control of wild oat, kochia, and field pennycress than either herbicide alone. Plant height, date of flowering, seed yield, and quality data indicated that safflower tolerated flurtamone alone up to 1.6 kg ha−1 and flurtamone tank mixed with ethalfluralin at rates as high as 1.1 plus 1.1 kg tar1, respectively. Safflower yield response to these herbicides was positive and reflected level of weed control attained with various treatments.

We modified a cereal huller to thresh seed of honey mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell]. The device threshes seed of other mesquite varieties, huisache [Acacia farnesiana (L.) Willd.], and other leguminous species.

The genetic diversity of 39 clones of common reed originating from different geographical areas of Iran were evaluated using morphological and RAPD analyses. High level of morphological variation was observed among clones. The 16 primers used in this study amplified 149 scorable RAPD loci among which 123 were polymorphic (83.1%). A dendrogram was prepared on the basis of a similarity matrix of RAPD data using the unweighted pair-group method with arithmetic averages (UPGMA) algorithm and separated the 39 clones into four groups, which mainly were in accordance with geographical origins. The results of the morphological comparison mostly corresponded with the results of RAPD analysis. It is possible that these variations among clones will affect successful management of common reed using chemical or the other methods of control.

Wild radish (Raphanus raphanistrum L.) is a problematic and economically damaging dicotyledonous weed infesting crops in many regions of the world. Resistance to the auxinic herbicides 2,4-D and dicamba is widespread in Western Australian R. raphanistrum populations, with the resistance mechanism appearing to involve alterations in the physiological response to synthetic auxins and in plant defense. This study aimed to determine whether these alterations cause inhibition in plant growth or reproduction that could potentially be exploited to manage 2,4-D–resistant populations in cropping areas. Therefore, the morphology and seed production of resistant and susceptible populations were compared in an outdoor pot study, with plants grown in the presence and absence of competition by wheat (Triticum aestivum L.). The susceptible and resistant R. raphanistrum populations were equally suppressed by wheat competition, with plant growth and seed production being decreased by approximately 50%. Although resistant populations produced less vegetative biomass than susceptible populations, there was no negative association between resistance and seed production. Therefore, it is unlikely that any nonherbicidal management practices will be more efficacious on 2,4-D–resistant than 2,4-D–susceptible R. raphanistrum populations.

When herbicides are sprayed in the field, a proportion of the herbicide falls onto leaves and soil surfaces, where it can be exposed to sunlight, generating photoproducts that can be more toxic and/or persistent than the parent substance and affect human health and the environment. The aim of this study was to identify the photoproducts of the herbicide alloxydim in leaf and soil model systems and to perform phytotoxicity studies. Alloxydim was rapidly photodegraded in systems simulating plant cuticles and soil surfaces, with half-lives ranging from 1 to 30 min. The main by-product, identified by LC-Qtof-MS as deallyoxylated alloxydim, was more stable than the active substance. The EC50 values on root lengths of different varieties of wheat plants and one grass weed ranged from 0.38 to 0.50 mg L−1 for alloxydim. In contrast, the EC50 values for deallyoxylated alloxydim ranged from 94 to 600 mg L−1 in the same species and in crops where the herbicide was applied. Special attention should be given to alloxydim degradation products because of the rapid degradation of this herbicide. Comparative bioassay studies between alloxydim and its photostable by-product showed that the by-product presents low phytotoxicity, whereas alloxydim can cause injury to neighboring and succeeding cereal crops.