This research compared seven field bindweed control treatments to a check in a 3-yr winter wheat-sorghum-fallow rotation. Treatments included 3 wk intervals of sweep tillage combined with one or two annual applications of 2,4-D (tillage and 2,4-D). Two other treatments were the same as tillage and 2,4-D, except dicamba or a mixture of picloram and 2,4-D were applied once in October after wheat harvest. A fourth treatment was identical to tillage and 2,4-D, except imazapyr was sprayed immediately after harvest of wheat. Also, three no-tillage systems using glyphosate and 2,4-D at monthly intervals were supplemented with either dicamba, picloram and 2,4-D, or imazapyr the same as in treatments involving tillage and 2,4-D. The check was sweep tilled every 6 wk. All treatments controlled field bindweed in one rotation of two fallow periods and two crops. After control was accomplished, wheat and sorghum yields were about twice the check. Using 1995 costs and returns, profit for an owner-operator for the two fallow periods and two crops was $123 ha−1 for tillage and 2,4-D, compared to $19 ha−1 for the check. Tillage and 2,4-D supplemented with picloram or imazapyr were almost as profitable as tillage and 2,4-D. Because of high herbicide cost and low yields, no-tillage treatments lost money. Profits with a 33:67 owner-tenant rental agreement were $105 and $21 ha−1, respectively, for owner and tenant using tillage and 2,4-D. With no field bindweed control practice, the tenant lost $33 ha−1 and the owner made $51 ha−1.

Biotypes of field bindweed that vary in sensitivity to glyphosate were studied to determine the physiological or biochemical bases for these differences. Studies con ducted using whole plants and in vitro cultured shoots identified several potentially important differences between the most tolerant (biotype 4) and most susceptible (biotype 1) biotypes. Biotype 4 plants had greater 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (DAHPS) activity and higher concentrations of phenolic compounds, indicating greater shikimate pathway activity than biotype 1. This may reflect a higher growth ability of biotype 4, as observed in shoot cultures. 5-Enolpyruvylshikimate-3-phosphate synthase (EPSPS) activity in whole plants increased in all parts of biotype 4 by 7 d after a glyphosate treatment of 1.1 kg ae ha−1, whereas activities in biotype 1 plants did not increase at any time. However, this may not be the only mechanism of glyphosate tolerance because EPSPS activity in cultured shoots of both biotypes increased equally in response to glyphosate, even though biotype 4 shoots were able to survive and grow on a glyphosate-containing medium that inhibited growth of biotype 1 shoots. We propose that multiple mechanisms operating at a cellular/metabolic level combine to enable biotype 4 to tolerate higher glyphosate rates than biotype 1.

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.

Field bindweed biotypes varying in susceptibility to glyphosate were studied to determine the role of glyphosate absorption and translocation in susceptibility differences. Absorption and translocation of radiolabeled glyphosate were measured after application to leaves of glyphosate-tolerant and -sensitive field bindweed biotypes grown under ambient, low, or high relative humidity (RH). Glyphosate injury and cuticle mass were also determined at both low and high RH. To avoid potential differences in susceptibility due to differential foliar absorption, glyphosate was fed to roots of hydroponically grown plants, and uptake, translocation, and injury patterns were also determined. Under ambient RH, no differences in foliar-applied glyphosate absorption or translocation were detected between field bindweed biotypes. The RH under which plants were grown influenced cuticle amounts, glyphosate absorption, and injury. Plants of both biotypes had less cuticular material when grown at high RH (80%) than at low RH (30%); however, more radioactivity was absorbed by the susceptible biotype at low RH. Regardless of RH regime, glyphosate injury was greater in the susceptible biotype than in the tolerant biotype. Glyphosate fed to roots of hydroponically grown plants was absorbed and translocated equally in the biotypes, yet relative differential glyphosate sensitivities were retained. These results suggest that differences in glyphosate susceptibility between field bindweed biotypes cannot be fully accounted for by differences in glyphosate absorption or translocation.

Although glyphosate controls many plant species, certain broadleaf weeds in Nebraska's cropping systems exhibit various levels of tolerance to the labeled rates of this herbicide, including ivyleaf morningglory, Venice mallow, yellow sweetclover, common lambsquarters, velvetleaf, kochia, Russian thistle, and field bindweed. Therefore, two field studies were conducted in 2004 and 2005 at Concord and North Platte, NE, to evaluate performance of (1) seven preemergence (PRE) herbicides and (2) glyphosate tank mixes applied postemergence (POST) at three application times for control of eight weed species that are perceived as problem weeds in glyphosate-resistant soybean in Nebraska. The PRE herbicides, including sulfentrazone plus chlorimuron, pendimethalin plus imazethapyr, imazaquin, and pendimethalin plus imazethapyr plus imazaquin provided more than 85% control of most weed species tested in this study 28 d after treatment (DAT). However, sulfentrazone plus chlorimuron and pendimethalin plus imazethapyr plus imazaquin were the only PRE treatments that provided more than 80% control of most weed species 60 DAT. In the POST glyphosate tank-mix study, the level of weed control was significantly affected by the timing of herbicide application; control generally decreased as weed height increased. In general, glyphosate tank mixes applied at the first two application times (early or mid-POST) with half label rates of lactofen, imazamox, imazethapyr, fomesafen, imazaquin, or acifluorfen, provided more than 80% control of all species that were 20 to 30 cm tall except ivyleaf morningglory, Venice mallow, yellow sweetclover, and field bindweed. Glyphosate tank mixes applied late POST with lactofen, imazethapyr, or imazaquin provided more than 70% control of common lambsquarters, velvetleaf, kochia, and Russian thistle that were 30 to 50 cm tall. Overall, glyphosate tank mixes with half label rates of chlorimuron or acifluorfen were the best treatments; they provided more than 80% control of all the studied weed species when applied at early growth stages. Results of this study suggested that mixing glyphosate with other POST broadleaf herbicides, or utilizing soil-applied herbicides after crop planting helped effectively control most problematic weeds in glyphosate-resistant soybean in Nebraska.

The effects of a gall mite (Aceria malherbae) and sublethal doses of either 2,4-DB or glyphosate on field bindweed growth were evaluated under laboratory conditions. Mite feeding reduced field bindweed shoot biomass 37 to 48% and root biomass 46 to 50%. 2,4-DB at 0.07 to 0.14 kg ae ha−1 or glyphosate at 0.14 to 0.28 kg ai ha−1 reduced field bindweed root biomass 25 to 52%. Combining A. malherbae feeding with either 2,4-DB or glyphosate application reduced root biomass of field bindweed plants more than mites or either herbicide alone. Live A. malherbae were present on field bindweed 3 wk after treatment with either herbicide. Combination of A. malherbae with sublethal herbicide doses may allow for field bindweed suppression while reducing potential herbicide injury to crops and maintaining A. malherbae populations.

Geostatistical techniques were used to describe and map weed spatial distribution in two sunflower fields in Cabello and Monclova, southern Spain. Data from the study were used to design intermittent spraying strategies. Weed species, overall infestation severity (IS) index, and spatial distribution varied considerably between the two sites. Weed species displayed differences in spatial dependence regardless of IS. The IS mapping of each single weed and of the overall infestation was achieved by kriging, and site-specific application maps were then drawn based on the multi-species weed map and the estimated economic threshold (ET). Herbicide treatment was assumed to be needed for an overall IS score of 2 or 3, and the infested “area exceeding the economic threshold” was determined. The overall weed-infested area varied considerably between locations. About 99 and 38% of the total area was moderately infested (IS ≥ 2) at Monclova and Cabello, respectively. Therefore, if a given herbicide were applied just to the areas exceeding the ET, a significant herbicide saving would be realized in Cabello but not in Monclova. A multi-species spatial analysis provides an opportunity to make site-specific management recommendations from a map of the distribution of IS of the total infestation. Furthermore, only in fields with hard-to-control weed species (e.g., nodding broomrape and corn caraway) would site-specific herbicide application maps developed from total weed infestations need to be complemented with targeted site-specific herbicide treatments to prevent further spread of these species, although their IS might be low.

Experiments were conducted to determine the efficacy, absorption, and translocation of glyphosate, glufosinate, and imazethapyr with selected weed species. In the greenhouse glyphosate, glufosinate, and imazethapyr were applied at 0.25, 0.5, and 1 times their label rates of 1,121, 410, and 70 g ha−1, respectively, on 10- to 15-cm black nightshade, common waterhemp, eastern black nightshade, field bindweed, giant ragweed, ivyleaf morningglory, prairie cupgrass, velvetleaf, and yellow nutsedge. Glyphosate applied at the 1-time rate caused injury greater than or similar to injury from the 1-time rate of glufosinate or imazethapyr on black nightshade, common waterhemp, eastern black nightshade, field bindweed, giant ragweed, prairie cupgrass, and velvetleaf. The 1-time rate of glufosinate injured ivyleaf morningglory and yellow nutsedge more than did the 1-time rate of glyphosate or imazethapyr. Under field conditions glyphosate caused the greatest injury to common waterhemp, prairie cupgrass, and velvetleaf across plant growth stages. Giant ragweed and ivyleaf morningglory injury was more dependent on growth stage, with the 15- and 30-cm growth stages more susceptible to glyphosate than to glufosinate or imazethapyr. Differential response of these weed species may be caused by differences in herbicide translocation. Glyphosate was translocated more in both giant ragweed and ivyleaf morningglory, and these species were injured more by glyphosate than by glufosinate or imazethapyr at the larger growth stages.

Vineyard weed communities were examined under the influence of an organic weed control practice, soil cultivation with a Clemens cultivator, and applications of the herbicide glyphosate. Experimental treatments (winter–spring glyphosate, spring cultivation, fall–spring cultivation, fall cultivation–spring glyphosate) were carried out in a California wine grape vineyard for 3 yr. Cultivation alone was not as effective as glyphosate, based on lower weed biomass in the glyphosate-only treatment in 2 of 3 yr. However, given that two passes with the Clemens cultivator decreased weed biomass relative to one pass, it is possible that additional passes could bring about further reductions. Pairing fall cultivation with glyphosate was as effective at reducing weed biomass as two glyphosate applications in 2 of 3 years, suggesting that substituting a glyphosate application with cultivation may be an effective method of reducing herbicide use in vineyards. Canonical correspondence analysis revealed significant treatment effects on community structure. Weed composition in the spring cultivation treatment was significantly different from that of all other treatments. Based on our findings of high relative abundance of field bindweed and sowthistle species, which are problematic vineyard weeds that grow into the vine canopy and disrupt canopy management practices, it is possible that either the presence of soil disturbance or the absence of herbicides favored these species.

Perennial weeds constitute a serious problem in Greek cotton-growing areas, as they strongly competing against the crop and downgrade the final product. Monitoring weeds at a regional scale and relating their occurrence with abiotic factors will assist in the control of these species. Purple nutsedge, field bindweed, bermudagrass, and johnsongrass were studied in cotton crops for three consecutive growing seasons (2007 through 2009) in a large area of central Greece. Weed densities and uniformities per sampling site were assessed in relation to soil and climatic data. Abundance index (AI), which is highly dependent on abiotic factors, was also estimated, and revealed purple nutsedge to the most persistent and damaging species among the recorded weeds. Field bindweed showed the highest correlation with soil properties and especially with clay content. Furthermore, correlation analysis was used over the sampling years in order to assess the stability of weed occurrence in the sampling sites. Purple nutsedge, field bindweed, and bermudagrass proved to be stable in location and intensity. The weed density spatial distribution was evaluated by using local indicators of spatial autocorrelation (LISA) statistics, and was mapped by ordinary kriging and co-kriging interpolation methods. Only 1 to 3 spatial outliers were identified in each 1 of the 3 yr. Between the two interpolation methods co-kriging delivered better results for field bindweed and purple nutsedge, indicating that soil data could improve the estimation of weed occurrence. These co-kriging interpolated weed maps would be a very useful tool for decision makers in taking appropriate weed control measures.

Intercropping is an eco-friendly approach for reducing weed problems through nonchemical methods. Intercrop effects on weed community structure have rarely been studied. A 6-yr study was initiated in 1999 and the response of aboveground weed flora (1999–2002 and 2005) and seed bank (2005) to the intercropping of saffron and black zira, two perennial crops was investigated. Mixtures consisted of 0/100, 25/75, 50/50, 75/25, and 100/0 saffron/black zira ratios, each planted at three densities: 30, 50, and 70 plant m−2. The effect of planting density on weed populations was variable and in most cases not significant. However, mixture ratios caused drastic species compositional changes in the weed community for which univariate and multivariate analyses explored four major associations: (1) weeds that favored a higher ratio of saffron in mixtures (e.g., grasses, field bindweed, pigweeds), (2) weeds that preferred a higher ratio of black zira in mixtures (e.g., Persian speedwell, Brassicaceae complex, Polygoaceae complex, and earthsmoke), (3) weeds that were more abundant in 50/50 mixtures (e.g., Caryophyllaceae complex), and (4) weeds that showed no specific pattern (e.g., common lambsquarterss). Pigweeds, prostrate knotweed, and common lambsquarters dominated the viable seed bank with relative densities of 48, 28, and 8%, respectively. The seed bank of most weed species responded to mixture ratios in a similar manner to those of their corresponding aboveground flora. Seed density decreased as soil depth increased, leading to the accumulation of 66, 22, and 12% of viable seeds in soil layers of 0–5, 5–15 and 15–25 cm, respectively. Greater weed and seed densities were found in more pure stands of black zira. These findings contribute to improving current understanding of crop–weed community structures and may help in developing weed management practices.

Four species of biocontrol insects (knapweed root weevil, lesser knapweed flower weevil, spotted knapweed seedhead moth, and bronze knapweed root borer) were released at a diffuse knapweed site located about 10 km east of the Colorado Front Range. Two other biocontrol agents (banded gall fly and knapweed seed head fly) were already present at this site. Densities of rosettes and flowering plants, seedhead production per plant, and seeds per seedhead on mowed and unmowed areas were studied for 5 yr, 1997–2001. Of the six biocontrols, five (Urophora spp., bronze knapweed root borer, knapweed root weevil, and lesser knapweed flower weevil) obtained sizable densities relative to weed abundance. Diffuse knapweed declined from 8.3% in absolute cover in June 2000 to 1.9% by September 2001. Vegetation transects closest to the insect release areas showed the largest declines, with diffuse knapweed disappearing entirely on one transect. In contrast, diffuse knapweed abundance at a nearby prairie increased during the same interval from an absolute cover value of 14.5 to 17%. Seed production of diffuse knapweed on the insect release site declined from nearly 5,000 seeds m−2 in 1997 to less than 100 seeds m−2 in 2001. Lesser knapweed flower weevil larvae appeared responsible for much of the seed reduction, whereas adults of this species were effective in damaging bolting plants. The extent to which grazing removal and individual insect species contributed to this reduction in diffuse knapweed abundance cannot be identified from this study. These results support the contention that a significant reduction in abundance of diffuse knapweed using insects is possible at least in some regions of the western United States.

Ten years of Oregon Seed Certification Service (OSCS) preharvest field inspections converted from a nonspatial database to a geographic information system (GIS) were analyzed for patterns in spatial distribution of occurrence and severity of the 36 most common weeds of grass seed crops. This was done under the assumptions that those patterns would be primarily consequences of interactions among farming practices, soil properties, and biological traits of the weeds, and that improved understanding of the interactions would benefit the grass seed industry. Kriging, Ripley's K-function, and both Moran's I spatial autocorrelation and Getis-Ord General G high/low clustering using the multiple fixed distance band option all produced roughly similar classifications of weeds possessing strongest and weakest spatial clustering patterns. When Moran's I and General G analyses of maximum weed severity observed within individual fields over the life of stands were conducted using the inverse distance weighting option, however, results were highly sensitive to the presence of a small number of overlapping fields in the 10-yr record. Addition of any offset in the range from 6 to 6,437 m to measured distances between field centroids in inverse distance weighting matrices removed this sensitivity, and produced results closely matching those for the multiple fixed distance band method. Clustering was significant for maximum severity within fields over the 10-yr period for all 43 weeds and in 78% of single-year analyses. The remaining 22% of single-year cases showed random rather than dispersed distribution patterns. In decreasing order, weeds with strongest inverse-distance spatial autocorrelation were German velvetgrass, field bindweed, roughstalk bluegrass, annual bluegrass, orchardgrass, common velvetgrass, Italian ryegrass, Agrostis spp., and perennial ryegrass. Of these nine weeds, distance for peak spatial autocorrelation ranged from 2 km for Agrostis spp. to 34 km for common velvetgrass. Weeds with stronger spatial autocorrelation had greater range between distance of peak spatial autocorrelation and maximum range of significance. Z-scores for General G high/low clustering were substantially lower than corresponding values for Moran's I spatial autocorrelation, although the same two weeds (German velvetgrass and field bindweed) showed strongest clustering using both measures. Simultaneous patterns in Moran's I and General G implied that management practices relatively ineffective in controlling weeds usually played a greater role in causing weeds to cluster than highly effective practices, although both types of practices impacted Italian ryegrass distribution. Distance of peak high/low clustering among perennial weeds was smallest (1 to 3 km) for Canada thistle, field bindweed, Agrostis spp., and western wildcucumber, likely indicating that these weeds occurred in patchy infestations extending across neighboring fields. Although both wild carrot and field bindweed doubled in average severity over the period from 1994 to 2003, wild carrot was the only weed clearly undergoing an increase in spatial autocorrelation. Soil chemical and physical properties and dummy variables for soil type and crop explained small but significant portions of total variance in redundancy and canonical correspondence analysis of weed occurrence and severity. Fitch-Morgoliash tree diagrams and Redundancy Analysis (RDA) and Canonical Correspondence Analysis (CCA) ordinations revealed substantial differences among soil types in weed occurrence and severity. Gi∗ local hot-spot clustering combined with feature class to raster conversion protected grower expectations of confidentiality while describing dominant spatial features of weed distribution patterns in maps released to the public.

The efficacy, absorption, translocation, and metabolism of thiencarbazone-methyl (TCM) in hedge bindweed, field bindweed, ivyleaf morningglory, tall morningglory, and wild buckwheat were evaluated in greenhouse experiments and field trials. Forty-eight hours after foliar microapplication, 14C-TCM absorption was highest in ivyleaf morningglory (60%), followed by field bindweed (50%), wild buckwheat (35%), tall morningglory (17%), and hedge bindweed (9%). In all species, 14C-TCM was translocated systemically. By 24 h after application, 14C-TCM was detected in all parts of the plants. The translocation pattern is species-specific, with more translocation in tall morningglory and wild buckwheat. In all vining weeds 14C-TCM was almost not metabolized whereas corn metabolized almost all 14C-TCM 48 h after application. The efficacy of TCM was analyzed using dose–response curves. Wild buckwheat had the lowest value for the dose at which 50% of the activity occurs (2.1 g ai ha−1 TCM), followed by hedge bindweed and ivyleaf morningglory. Field studies confirmed the high control of wild buckwheat with TCM. Even at the lowest tested concentration of TCM, wild buckwheat was controlled by over 90%. In contrast, efficacy of TCM in field trials against perennial vining weeds was very low, 25% for field bindweed and 65% against hedge bindweed. Control efficacy could be well explained by the translocation pattern of TCM in vining weeds.