In laboratory studies, the herbicide 3'-chloro-2-methyl-p-valerotoluidide (solan) when applied to soil was transformed in part to 3,3'-dichloro-4,4'-dimethylazobenzene. The biochemically mediated transformation followed the pattern established previously for 3,4-dichloroaniline-based acylanilides, but the 3-chloro-4-methylaniline intermediate did not accumulate. Compared to 3,4-dichloroaniline-based acylanilides, solan yielded less azo residue and did not inhibit soil respiration, even if applied at 200 times the recommended field rate.

Managing weeds in lawns using cultural practices such as mowing, irrigation, and fertilization may be important in integrated management. A field experiment evaluated the impact of cultural factors on weed populations in St. Augustinegrass turf. Irrigation treatments were daily to replace evapotranspiration (“Daily”), weekly to saturate the root zone only when wilted (“Conditional Weekly”), and as needed to saturate the root zone after severe wilt (“Severely Wilted”). Averaged over 3 yr, the Daily, Conditional Weekly, and Severely Wilted irrigation treatments resulted in 30, 6, and 2% dollarweed cover, respectively. Except for dollarweed and mat lippia, the largest cover of other weeds was under Severely Wilted irrigation. Fertilization rates were 0, 14, or 28 g N m−2 yr−1; in 2002, the highest fertilization rate had the smallest cover of weeds other than dollarweed. Mowing heights were 64, 89, or 114 mm; in 2003, the shortest mowing height had the smallest cover and dry weight of weeds other than dollarweed. After 3 yr of cultural management, most plots were excessively weedy, and turfgrass quality for all cultural management-treatment combinations, in the absence of herbicides, was unacceptable.

Arabidopsis complementary DNA (cDNA) microarrays were hybridized with labeled cDNA from mature leaves and emerging tillers of wild oat to determine if they could identify gene expression profiles in distantly related species. More than 23% of the > 11,000 cDNAs on the array hybridized to the wild oat probe. Transcription patterns detected by hybridization to the arrays are indicators for physiological processes in the tissues tested. Coordinated expression patterns for these genes in Arabidopsis indicate common signals involved in their regulation. The results demonstrate that probing cDNA-based arrays from well-characterized species can provide valuable insight into the signal transduction processes regulating growth and development of poorly characterized species.

Greenhouse and field studies demonstrated that naptalam reduced paraquat activity by as much as 30% on sicklepod, smallflower morningglory, Florida beggarweed, and peanut Sequential application experiments, i.e. naptalam applied 2 or 24 h prior to an application of paraquat, as well as absorption studies utilizing 14C-paraquat, indicated that the antagonism was due largely to reduced paraquat absorption. Scanning electron microscopy revealed that application of naptalam, as well as naptalam applied with paraquat, resulted in amorphous deposits on the leaf surface which may account for the antagonism.

The activity of glyphosate [N-(phosphonomethyl)glycine], formulated as the isopropylamine salt, on in vitro photosynthesis was investigated. When pH 4.7 glyphosate solutions were titrated to a pH equal to that of the reaction media (pH 7.8), glyphosate additions had no effect on whole chain electron transport between coupled photosystem II (PS II) and photosystem I (PS I) in stroma-free chloroplast thylakoids from peas (Pisum sativum L. ‘Morse's Progress No. 9′). Inhibition did not occur even after a 2-h dark incubation of lamellae in a 5-mM solution of glyphosate. Fluorescence studies failed to detect an effect of glyphosate on PS-II mediated electron transport processes or upon light harvesting properties of PS II even after a 2-h glyphosate/chloroplast preincubation. Glyphosate had no effect on cyclic and noncyclic photophosphorylation even after a 100-min dark incubation of chloroplast membranes in a 5-mM solution of glyphosate. Based on these assays it is concluded that glyphosate has no direct effect on the photochemical reactions of photosynthesis when the pH of the active compound is adjusted to that of the reaction mixture prior to addition to a chloroplast suspension.

Research was conducted in 1994 and 1995 to evaluate the field mobility of flumetsulam in three soils of varied texture and organic matter content but constant pH (pH = 6.0 ± 0.1). Flumetsulam was monitored to a depth of 122 cm at 28, 56, and 84 days after treatment (DAT). Flumetsulam concentrations were determined by cotton bioassay, with separate standard curves for various soil–depth combinations. Following a preemergence application of flumetsulam at 224 g ai ha−1, the herbicide was primarily limited to the upper 8 cm of soil, regardless of soil type, year, or DAT. Exceptions to this typically occurred following substantial rainfall amounts early in the season. Beyond 28 DAT, no significant concentrations of flumetsulam were detected below 15 cm. Results from this research suggest that leaching is not a significant route of flumetsulam dissipation in the field.

The effects of five preemergence herbicides on turfgrass quality and control of crabgrass (Digitaria spp.) were measured to determine the influence of thatch on preemergence herbicide activity in Kentucky bluegrass (Poa pratensis L.) turf. Field applications of benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine), oxadiazon [2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-Δ2-1,3,4-oxadiazolin -5-one], and prosulfalin {N-[[4-(dipropylamino)-3,5-dinitrophenyl] sulfonyl]-S,S-dimethylsulfilimine} to thatchy Kentucky bluegrass turf in spring caused injury that was apparent during periods of summer stress, while DCPA (dimethyl tetrachloroterephthalate) and bensulide [O,O-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl)benzenesulfonamide] caused little or no injury. The same treatments on thatch-free sites revealed that only prosulfalin was injurious. Adsorption of benefin, bensulide, and DCPA from solution was greater by thatch than by soil; however, the mobility of these herbicides in undisturbed thatch profiles was greater than measured in undisturbed surface soil from thatch-free sites. Thus, turfgrass injury from preemergence herbicides on thatchy sites is due to at least two factors: the greater mobility of preemergence herbicides in thatch than in soil; and the inherent susceptibility of Kentucky bluegrass to injury from preemergence herbicides that come into direct contact with roots and other absorbing organs.

Retention, absorption, translocation, and metabolism of propanil (3′,4′-dichloropropionanilide) in tolerant wheat (Triticum aestivum L. ‘Era’) and susceptible green foxtail [Setaria viridis (L.) Beauv. ♯3 SETVI] were studied to determine the basis of selectivity. Green foxtail retained 7.7 times more spray on a mg/g fresh weight basis than did wheat. Absorption of 14C-propanil by green foxtail was greater than by wheat during most of the 48-h uptake period, but differences in absorption were not large enough for absorption to be a major selectivity factor. Translocation of foliar-applied 14C-propanil was limited in both species; after 48 h, 96.7% of absorbed 14C remained in the treated wheat leaf and 99.7% remained in the treated green foxtail leaf. Limited metabolism of 14C-propanil occurred in green foxtail, with only 6.4% of extractable 14C-propanil metabolized to dichlorolactanilide and unknown 14C-compounds during a 72-h period. Wheat metabolized 65.8% of the extractable 14C-propanil to dichloroaniline and unknown 14C compounds by 72 h after treatment. The results of this research indicate that spray retention and propanil metabolism are the major factors involved in wheat tolerance and green foxtail susceptibility to propanil.

In rolling topography, soil and water runoff losses can be greatly reduced by conservation production systems. Alfalfa (Medicago sativa L.) is an important crop in Nebraska and other states which is often followed in the crop sequence by corn (Zea mays L.) or sorghum [Sorghum bicolor (L.) Moench]. Three years of field experiments indicated that herbicides can substitute for erosive moldboard plowing to destroy alfalfa without loss in the subsequent corn yield. Herbicides applied just prior to corn planting in the spring gave more consistent alfalfa control than those applied the preceeding fall. The most consistent treatment used for alfalfa control and supplemental annual weed control while producing maximum corn yield was 2,4-D amine [(2,4-dichlorophenoxy) acetic acid] plus dicamba (3,6-dichloro-o-anisic acid) at 1.12 and 0.28 kg/ha, respectively. Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] plus propachlor (2-chloro-N-isopropylacetanilide) versus no preemergence herbicide was used for annual weed control in addition to the treatments to control alfalfa. This treatment was essential for maintaining corn yields where a non-residual or limited residual herbicide was used for alfalfa control.

The role of ethylene in kochia injury following the application of dicamba and other auxinic herbicides is not known. Experiments were conducted to evaluate kochia response to ethylene generated within plant tissue and to quantify ethylene emission from kochia following dicamba application to determine if ethylene production could be used to differentiate between dicamba-susceptible (S) and dicamba-resistant (R) kochia accessions. Dicamba at 0.28 kg ha−1 and fluroxypyr at 0.28 kg ha−1 caused severe stem and petiole twisting within 6 h of application, with S kochia exhibiting a greater level of epinasty than R kochia and fluroxypyr causing more epinasty than dicamba. Fluroxypyr provided similar control of S and R kochia, but dicamba provided less control of R kochia than S kochia. Ethylene evolution in S kochia from ethephon at 1.1 kg ha−1 and dicamba at 0.28 kg ha−1 was similar, approximately 70 ng (g fresh weight)−1 h−1. Elevated ethylene concentration from as much as 2 kg ha−1 ethephon did not produce epinastic symptoms or other plant response in S or R kochia. Ethylene evolution following dicamba application increased with time up to 48 h after application and with increasing dicamba rate up to 0.56 kg ha−1, which were the end points of the research. Ethylene evolution from the S accession was 2.5 times that of the R accession averaged across dicamba rates and harvest times. The greatest difference in ethylene evolution between S and R accessions occurred 24 h after treatment at 0.14 kg ha−1 dicamba, with S kochia producing ethylene at 470%, compared with R kochia.

Studies were conducted to determine the effects of scarification, temperature, osmotic potential, and pH on seed germination of buffalo gourd and to examine seedling emergence and establishment. Mechanical and chemical scarification did not increase germination compared to non-scarified seed. Seed germinated at constant temperatures in the dark from 15 to 37 C with optimum germination at 25 C. As osmotic potentials became more negative from −0.1 to −0.8 MPa, germination decreased from 77 to 53%. Germination increased from 15% at pH 2.2 to 90% at pH 8. Seedlings were able to emerge from depths as great as 12 cm, and plants younger than 19 d were not able to sprout from the roots when the shoots were removed.

Two winter wheat cultivars are known to differ in sensitivity to metribuzin: TAM W-101 (tolerant) and Vona (sensitive). Their reciprocal F1, reciprocal F2, and backcross populations were compared to determine the genetic expression of metribuzin sensitivity. TAM W-101 showed a much wider range of response to metribuzin than Vona with little overlap between the two distributions. Both sets of reciprocal F1 and F2 populations resembled Vona in metribuzin response, but the variances of maternal TAM W-101 populations exceeded those of maternal Vona populations. Genetic segregation in metribuzin response was expressed in TAM W-101/Vona F2 but not in Vona/TAM W-101 F2. The greater variability observed in the metribuzin-tolerant parent TAM W-101 and maternal TAM W-101 populations could not simply be interpreted as the result of differential sampling of male and female gametes from TAM W-101.

The 14C-AC 263,222 was foliar applied to common cocklebur, johnsongrass, peanut, sicklepod, and soybean in order to study translocation and metabolism characteristics in each species. Differential absorption of 14C-AC 263,222 between species was evident 4 h after application. At 48 h after application, sicklepod and peanut absorbed more 14C-AC 263,222 than johnsongrass, common cocklebur, or soybean. Translocation of 14C-AC 263,222 and its metabolites out of the treated leaves increased with time for all species. The 14C-AC 263,222 and its metabolites appear to be both xylem- and phloem-mobile based on patterns of movement. Absorption and translocation differences occurred between species; however, they did not appear to explain differential species response. Metabolism of 14C-AC 263,222 differed greatly among species. Common cocklebur metabolized less 14C-AC 263,222 than any other species 96 h after application. Johnsongrass and sicklepod metabolized 24 and 28% of the 14C-AC 263,222, respectively, 96 h after application. Peanut and soybean metabolized 76 and 62%, respectively, of the 14C-AC 263,222 96 h after treatment. The half-life of 14C-AC 263,222 was 1.1, 2.5, 7.7, 11.6, and 34.5 d in peanut, soybean, sicklepod, johnsongrass, and common cocklebur, respectively. Differential tolerance of species appears to be directly related to the half-life of AC 263,222 in the plant.

Pollen movement between individuals can increase the rate of herbicide resistance evolution by spreading resistance alleles within or between populations and by facilitating the rapid accumulation of resistance alleles within individuals. This study investigated the level of pollen-mediated gene flow between paraquat-resistant and paraquat-susceptible populations of the self-pollinated weed species hare barley. The experiment was conducted in both directions, from resistant to susceptible and susceptible to resistant, across 2 yr. To maximize the potential for pollen flow, individual plants were grown in a single pot. The level of gene flow was similar across years and between genotypes. The level of pollen-mediated gene flow ranged from 0.06 to 0.15%. Gene flow from resistant to susceptible plants was confirmed by demonstrating segregation for resistance in the progeny of suspected crosses. This study suggests that pollen-mediated gene flow will occur in this species at frequencies less than 0.16% and could assist the accumulation of resistance alleles within a population. These low levels of gene flow through pollen movement suggest that cross-pollination over larger distances would be unlikely and pollen movement probably does not contribute to gene flow between populations.

4–Chloro–2–butynyl N–(3–chlorophenyl)carbamate (S–847) has been reported to show promise for selective control of wild oats in wheat, barley, flax, sugar beets, and peas. This paper presents data on the influence of several treatment conditions on wild oat control.

The cotton-producing industry today faces a real challenge in its attempt to control weeds in cotton. It is a problem with many facets. Differences in weed species, topography, soil type, scale of operation, rainfall, and many other factors make it difficult to develop single practices that work satisfactorily across large areas of the Cotton Belt.

The mesquite tree (Prosopis spp.) has been invading southwestern ranges to an alarming degree during the last half century, and has become a serious competitor for available moisture and light with perennial grass—the principal forage of livestock in this area. Its distribution in Arizona, New Mexico, and Texas has been estimated at over 70 million acres. Of the three varieties of mesquite found in these States, velvet mesquite (P. juliflora var. velutina (Woot.) Sarg.) is essentially limited to Arizona, and is the most common variety found therein.

These herbicides at rates of .01 to .25 lb/A caused moderate to severe morphological effects on soybeans and significant yield reductions. Soybeans treated in the vegetative stage were injured more than those treated in the bloom stage. The herbicide 2-(2,4,5-trichlorophenoxy)propionic acid (silvex) injured soybeans most followed by 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), 2,4-dichlorophenoxyacetic acid (2,4-D), and 4-(2,4-dichlorophenoxy)-butyric acid (2,4-DB), in that order.

Since the commercialization of herbicide-resistant (HR) crops, primarily glyphosate-resistant crops, their adoption has increased rapidly. Multiple herbicide resistance traits in crops such as canola (Brassica napus L.), corn (Zea mays L.), cotton (Gossypium hirsutum L.), and soybean [Glycine max (L.) Merr.] have become available in recent years, and management of their volunteers needs attention to prevent interference and yield loss in rotational crops. The objectives of this review were to summarize HR crop traits in barley (Hordeum vulgare L.), canola, corn, cotton, rice (Oryza sativa L.), soybean, sugarbeet (Beta vulgaris L.), and wheat (Triticum aestivum L.); assess their potential for volunteerism; and review existing literature on the interference of HR crop volunteers, yield loss, and their management in rotational crops. HR crop volunteers are problem weeds in agronomic cropping systems, and the impact of volunteerism depends on several factors, such as crop grown in rotation, the density of volunteers, management practices, and microclimate. Interference of imidazolinone-resistant (IR) barley or wheat volunteers can be a problem in rotational crops, particularly when IR crops such as canola or wheat are grown. HR canola volunteers are abundant in the Northern Great Plains due to high fecundity, seed loss before or during harvest, and secondary seed dormancy, and they can interfere in crops grown in rotation such as flax (Linum usitatissimum L.), field peas (Pisum sativum L.), and soybean. HR corn volunteers are competitive in crops grown in rotation such as corn, cotton, soybean, and sugarbeet, with yield loss depending on the density of HR corn volunteers. Volunteers of HR cotton, rice, soybean, and sugarbeet are not major concerns and can be controlled with existing herbicides. Herbicide options would be limited if the crop volunteers are multiple HR; therefore, recording the cultivar planted the previous year and selecting the appropriate herbicide are important. The increasing use of 2,4-D, dicamba, glufosinate, and glyphosate in North American cropping systems requires research on herbicide interactions and alternative herbicides or methods for controlling multiple HR crop volunteers.

The quantities of chloroplast proteins and chlorophyll were lower in oat plants treated 6 days with 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) than in the controls. Radioactive amino acid incorporation into chloroplasts indicated that the reduced levels of protein resulted from reduced synthesis. Glucose improved the amino acid incorporation in the treated tissue, but still the rate was reduced markedly by the simazine treatment. An effect of simazine even in darkness on amino acid incorporation into chloroplasts was suggested by the data. Total ribonucleic acid (RNA) content and synthesis as measured by incorporation of p32 were altered by simazine treatments.