The 14C-labelled insecticide, 2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate (carbofuran), supplied to the roots of barley (Hordeum vulgare L. ‘Larker’) and corn (Zea mays L. ‘Mich 400’) seedlings was readily taken up and transported to the shoots. Alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] did not inhibit carbofuran metabolism in barley or corn. Butylate (S-ethyl diisobutylthiocarbamate) slightly inhibited carbofuran metabolism in corn roots. Chlorbromuron [3-(4-bromo-3-chlorophenyl)-1-methoxy-1-methylurea] inhibited carbofuran metabolism by decreasing the concentration of 14C found in the acetone-insoluble residue and the methanol-soluble fraction in barley shoots. Chlorbromuron increased the carbofuran content and decreased the 2,3-dihydro-3-hydroxy-2,2-dimethyl-7-benzofuranyl methylcarbamate (3-hydroxycarbofuran) content of the chloroform-soluble fraction in both barley shoots and roots. Chlorbromuron did not affect carbofuran metabolism in corn.

Inhibition of net photosynthesis of jointed goatgrass and downy brome protoplasts by metribuzin and its ethylthio analog (ethyl-metribuzin) was greater at 25 than at 10 C. As temperature increased from 10 to 25 C, the concentration of ethyl-metribuzin required to inhibit net photosynthesis 50% (I50) decreased by a factor of 3.5 and 4.3, respectively, in jointed goatgrass and downy brome. I50 values for metribuzin decreased by a factor of 1.5 and 2.5 in jointed goatgrass and downy brome, respectively, for the same 15 C increase in temperature. Based on I50 values at 10 C, metribuzin was nine times more inhibitory than ethyl-metribuzin in jointed goatgrass and eight times more inhibitory in downy brome. At 25 C, metribuzin was only 4.7 and 3.9 times more inhibitory than ethyl-metribuzin in jointed goatgrass and downy brome, respectively. Thus, cold temperatures reduced the activity of ethyl-metribuzin more than metribuzin. The activity of both herbicides was reduced less in protoplasts of jointed goatgrass than in protoplasts of downy brome over the 15 C range.

The effect of repeated inoculations of the rust Puccinia cardui-pycnocephali Sydow (Uredinae) on growing rosettes of Mediterranean specimens of slenderflower thistle (Carduus tenuiflorus Curt. ♯3 CRUTE) and Italian thistle (Carduus pycnocephalus L. ♯ CRUPY), and Australian specimens of Italian thistle was investigated, using a Mediterranean strain of the rust collected mainly on Italian thistle. Growth of slenderflower thistle was not affected, but growth of both specimens of Italian thistle was decreased significantly when inoculated with the rust. This decrease was significantly higher on Australian specimens.

The winter wheat production system of the Pacific Northwest is characterized by severe wind and water erosion and winter annual grass weeds requiring high herbicide input. Since 1985, numerous multi- and interdisciplinary, long-term, large-scale, integrated cropping systems studies have been or are currently being conducted. The primary focus of these studies was on weed biology, ecology, and management, whereas secondary evaluations were on alternative cropping systems, conservation tillage, and fertilizer or herbicide inputs. The 6-yr integrated pest management project, conducted in the high-rainfall zone (> 400 mm), showed for the first time that when weeds were adequately managed, conservation production systems were more profitable than conventional systems. In the intermediate rainfall zone (350 to 400 mm), a recently concluded 6-yr, three-state study integrated single-component research results into a multifaceted approach to managing jointed goatgrass. This project has been used as a model study for other western states and the National Jointed Goatgrass Research Initiative. At present (9 yr thus far), a study is being conducted in the low-rainfall zone (< 350 mm) to examine the feasibility of no-till spring cropping systems in lieu of the highly erosive, weed infested, wheat–fallow system. Because of these projects, the Washington Wheat Commission recognized the importance of long-term, interdisciplinary, cropping systems research and has therefore established an Endowed Chair at Washington State University for direct seed cropping systems research. Federal, national, and regional agencies have used information from these projects for farm plans and pesticide usage.

Transgenic Nicotiana tabacum with tolerance to 2,4-D has previously been produced using a bacterial 2,4-D-dioxygenase gene (tfdA) driven by the 35S promoter of cauliflower mosaic virus. Using promoters from the Pisum sativum plastocyanin gene (petE) and an Arabidopsis thaliana histone gene (H4A), we demonstrate that similar protection from 2,4-D can be obtained in transgenic N. tabacum by targeting expression of tfdA to either meristematic tissues or chloroplast-containing tissues. As with the 35S promoter constructs, the plants are tolerant but not completely resistant; very young seedlings in particular are only slightly protected. However, the levels of tolerance observed could offer a useful degree of protection from accidental spray drift.

Cooperative research was initiated by a multidisciplinary team of weed scientists and agricultural economists in 1975 that laid the foundation for integrated weed management research in Colorado. Colorado's integrated weed management research has four phases: weed seed bank decline, systems approach to weed management, bioeconomic modeling, and multiple weed management tactics. Each phase considered weed seed bank, weed control efficacy, weed control costs, crop yield, and gross margin. All four phases emphasize the need for a weed management system that minimizes seed production in situations where a high soil weed seed bank exists. However, once the weed seed bank is reduced, a weed management program with less than 100% weed control can be employed without increasing the seed bank. Intensive weed management systems are seldom justified when economics, weed control, and weed seed bank are considered. Integrated weed management approaches require integrating crop and weed biology with management tactics. Integrated weed management requires advanced managerial skills and often more time than traditional approaches.

Wild poinsettia is a serious weed in several crops, including peanut, grown in the southeastern United States. A study was conducted over 3 yr at Jay, FL, to characterize the growth and development of wild poinsettia grown from seed collected at Plains, GA; Marianna, FL; and Baton Rouge, LA. Seedlings from each selection were transplanted to the field and were grown either alone or in competition with peanut. Observations made throughout the growing season indicated that the Louisiana selection flowered later, grew to a larger size, produced more leaf area and biomass, and caused greater light attenuation and peanut yield reduction than the other two selections. The Georgia selection produced the smallest plants, least leaf area and biomass, and was least competitive with peanut. The Florida selection was intermediate for these parameters. Wild poinsettia dry biomass production was reduced by 78 to 83% when grown with peanut compared with monoculture wild poinsettia.

The selectivity mechanisms of sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} were investigated by examining absorption of 14C-sethoxydim into tissues of corn (Zea mays L. ‘Goldencrossbantam′) and pea (Pisum sativum L. ‘Alaska′). Greater absorption of 14C-sethoxydim was observed only into the proliferative 2-mm terminals of the excised roots of susceptible corn, and the same result was obtained with corn seedlings in hydroponic culture. Absorption was not affected by 1 × 10−4 M 2,4-dinitrophenol (DNP), which indicated that the absorption of 14C-sethoxydim is probably mediated by a passive transport system rather than an active transport system. The selective herbicidal action of sethoxydim appeared to depend largely on the differential rates of absorption into meristematic regions by the susceptible and tolerant plants.

Several herbicides were evaluated for their ability to control duncecap larkspur, a serious poisonous plant on mountain rangelands in the western U.S. Duncecap larkspur density was reduced from 33 to 93% by triclopyr applied at 2.2, 4.5, and 9.0 kg ae/ha. Picloram applied at 2.2 and 4.5 kg ae/ha reduced density from 33 to 99%. Metsulfuron applied at 86 and 138 g ai/ha reduced density from 50 to 98%. Glyphosate was the most effective herbicide, reducing density by 90 to 100% when applied at 2.2 kg ai/ha. Glyphosate reduced the cover of grasses and perennial forbs but increased cover of annual forbs. All rates of picloram and metsulfuron reduced forb cover. Grass cover increased in most plots where duncecap larkspur and forbs were reduced.

Downy brome seed production was measured in the field following the establishment of different moisture levels using a line source sprinkler irrigation system. Results indicated that seed production was strongly affected by different moisture levels, with a curvilinear decrease in seed number from higher to lower moisture. In a hydroponic study with water deficits induced by PEG-8000, no seeds were produced when plants were severely stressed (-1.1 MPa) for a 7-day period during culm elongation or anthesis. Number of seeds/panicle was reduced under severe water stress during seed fill, under moderate stress (-0.5 MPa) during anthesis or seed fill, and under mild stress (-0.1 MPa) during anthesis. Water stress also reduced apparent photosynthesis and increased diffusive resistance of flag leaves, particularly under severe stress. In general, water deficits did not affect seed weights or germination percentages in either study.

In field studies, sprinkler irrigation application of the butyl ester of fluazifop-P, the methyl ester of haloxyfop, and the ethyl ester of quizalofop controlled large crabgrass as well as conventional spray applications. In greenhouse investigations, root uptake of the herbicides from sprinkler irrigation applications injured large crabgrass more than root uptake from conventional applications, but large crabgrass injury from shoot uptake was equal with sprinkler irrigation and conventional applications. Droplets with dilute concentrations of herbicide and crop oil, simulating sprinkler irrigation, were more active when applied to the whorl or second leaf than to the first leaf of large crabgrass. An increase in concentration of nonemulsified oil in the treatment solution increased herbicide deposition and retention.

Leaching of EPTC (S-ethyl dipropylthiocarbamate) plus R-25788 (N,N-diallyl-2,2-dichloroacetamide) through columns of four soils resulted in the separation of R-25788. Separation of R-25788 from EPTC was greater in coarser than in finer textured soils. When soil columns were placed under drying conditions for 6 days after leaching, R-25788 moved upward in the columns faster than EPTC.

The growth of germinating wild oat seedlings (Avena fatua L.) in soil treated with a range of concentrations of the individual isomers of diallate [S-(2,3-dichloroallyl)diisopropylthiocarbamate] and mixtures thereof has been studied. on the basis of diallate concentration required to reduce height by 50%, the cis isomer is less effective than the trans isomer by about 65%. A mixture of 42% trans and 58% cis diallate is shown to exhibit an antagonistic effect of about 95%. The trans isomer is more effective than the 42/58 mixture by a factor of 2.6. It is shown that height vs concentration response curves can be represented by y = A {(x/C)B + 1}-1, where y = height and x = concentration. A computer program has been developed to find the best parameters A, B, and C from any set of individual response data. A new technique for calculating synergism or antagonism has been employed in the part dealing with mixtures of diallate.

The basis for increased phytotoxicity of foliar-applied atrazine at high temperature in common bean and redroot pigweed was investigated. Plants were grown under low (15/10 C), medium (25/20 C), or high (35/30 C) temperature regimes. Atrazine absorption by plants grown under different temperatures increased with increasing temperatures in both species. Greater than 90% of absorbed atrazine remained in treated leaves and translocation was not altered by temperature in both species. Metabolism of atrazine by both hydroxylation and glutathione-conjugation was greater in plants grown at 35/30 than 15/10 C in both species. Foliar-applied atrazine reduced extractable photosystem II (PS II) activity as temperature increased in both species. Studies were also conducted on thylakoid membranes from plants not treated with atrazine. The I50 for atrazine inhibition of PS II decreased and affinity of atrazine binding to thylakoid membranes increased as temperature increased in both species. We concluded that the increased phytotoxicity of atrazine at high temperatures is caused by enhanced foliar absorption and greater affinity of atrazine for the binding site.

Uptake, translocation, and metabolism of 14C-terbacil was investigated in 12-leaf (tolerant) and 3-leaf (susceptible) field violet plants. Field violets with 12 leaves absorbed less 14C-terbacil g−1 of fresh weight from solution culture than did plants with three leaves. Plants with three leaves translocated twice as much radioactivity to foliage than did plants with 12 leaves. Most 14C in roots (77%) and foliage (57%) of field violet plants with 12 leaves was in polar metabolites. Metabolism studies indicated that most 14C (79%) in foliage extracts from field violet plants with three leaves was 14C-terbacil. Polar metabolites were not detected in roots of field violet plants with three leaves.

A belt-carried small-plot sprayer for field research work was constructed. Spray materials are prepared in 1-quart polypropylene bottles, and these are placed directly in the pressure canister of the sprayer for application. The system is charged by a CO2 pressure source and the spray applied through conventional booms.

The movement and persistence of 4-amino-3,5,6-trichloropicolinic acid (picloram) in an Osborne clay soil was determined over a 4-year period. Picloram concentrations were determined with soybean (Glycine max (L.) Merr. ‘Altona’) as the bioassay plant. Application rates ranged from 35 to 700 g/ha. Movement and dissipation of picloram were neglible under low soil moisture conditions, but under high rainfall conditions picloram was leached into the 30 to 60-cm depth. A greater percent of the picloram was leached at the higher application rates. Dissipation increased with temperature (days over 27 C) and decreased with increasing depth in the soil profile. Two applications of picloram at 70 g/ha applied in 2 successive years showed no detectable accumulation, but accumulation occurred from two applications of 350 g/ha; 32% of the activity remained after approximately 2 years.

Picloram (4-amino-3,5,6-trichloropicolinic acid) and tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} were the most effective herbicides for killing Macartney rose (Rosa bracteata Wendl.) on the Claypan Resource Area of Texas. At 4.5 kg/ha picloram (ae/ha) and tebuthiuron (ai/ha) as sprays killed 70% of the plants and as pellets 73 and 84% 1 yr after application, respectively. Bay Met 1486 {N-[5-(ethylsulfonyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea}, buthidazole {3-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-4-hydroxy-1-methyl-2-imidazolidinone}, 2,4-D [(2,4-dichlorophenoxy) acetic acid], 3,6-dichloropicolinic acid, glyphosate [N-(phosphonomethyl)glycine], hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione], and triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid} were markedly less effective than either picloram or tebuthiuron. After 2 to 4 months, 2,4-D, picloram, picloram + 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid], and triclopyr reduced the Macartney rose canopy by at least 95%, but only picloram and tebuthiuron controlled Macartney rose after 3 yr. Sprays of glyphosate and hexazinone inhibited growth of grasses after 3 months. Most herbicide sprays reduced broadleaf cover for at least 3 months.

Indirect effects of insect control strategies on weed populations are important to consider when developing robust integrated pest management strategies. Weed seed predation rates were investigated in corn managed under three contrasting treatments based on control practices for corn rootworm: (1) the transgenic crop Cry3Bb Bt corn, (2) the broad-spectrum insecticide tefluthrin, and (3) no insecticide control. This 2-yr field study conducted near Ithaca, NY, involved quantifying seed loss from velvetleaf, common lambsquarters, and giant foxtail in arenas with and without vertebrate exclosures. Velvetleaf and giant foxtail were unaffected by the insecticide treatment; however, average seed predation of common lambsquarters was lower in both the Bt corn (11.9%) and insecticide-treated plots (11.8%) compared with control plots (17.5%) that did not receive any insecticide. Seed predation of common lambsquarters was not affected by the vertebrate exclosure. Lower seed predation in the transgenic Bt corn and insecticide treatments was likely due to nontarget effects on carabids (Coleoptera: Carabidae). Although the reduction in seed predation was modest and limited to only one of the three weed species tested, our results highlight the need for greater risk assessment that includes the ecosystem service of weed seed predation when considering insect pest management options.

Dark germination of light-requiring lettuce seeds (Lactuca sativa L. ‘Grand Rapids’) was stimulated by SAN 9789 [4-chloro-5-(methylamino-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone] and to a minor degree by BASF 13761 [4-chloro-5-methoxy-2-phenyl-3(2H)-pyridazinone] and BASF 44521 [4-chloro-5-methoxy-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone], but not by’ pyrazon [5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone], SAN 9785 [4-chloro-5-(dimethylamino)-2-phenyl-3 (2H)-pyridazinone], SAN 9774 [5-amino-4-chloro-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone], or SAN 6706 [4-chloro-5-(dimethylamino)-2-(α,α,α-trifluoro-m-tolyl)-3(2H)-pyridazinone]. SAN 9789 stimulation was inhibited by cis-4-cyclohexene-1,2-dicarboximide (CHDC), and abscisic acid (ABA) at 1 × 10-4 M. Red light nullified the inhibitory effect of CHDC (1 × 10-4 M) but not the inhibitory effect of ABA (1 × 10-4 M) on SAN 9789 stimulated germination. Gibberellic acid (GA3) and kinetin (6-furfurylaminopurine) increased the germination stimulatory effect of SAN 9789 in darkness. Temperatures above 25 C decreased the effect of SAN 9789, with a temperature of 35 C completely inhibiting germination. The inhibitory effect of CHDC was strongly decreased at temperatures below 20 C. SAN 9789-induced germination in darkness was always the same (25 to 26% units increase in germination) even though the red light-stimulated germination differed with the seed batch.