Weed interference experiments have not been extensively conducted in Oklahoma peanut. Research was conducted in three environments to evaluate usefulness of single-weed density experiments with the use of several weeds to measure their relative competitive abilities with a crop. These data can be used to validate current competitive indices (CIs) used by a model to predict peanut yield loss due to weeds. This model is used by the Herbicide Application Decision Support System (HADSS) and Pesticide Economic and Environmental Tradeoffs (PEET), two decision-support systems (DSSs) available for Oklahoma peanut. Six weeds common in Oklahoma peanut were used: crownbeard, eclipta, ivyleaf morningglory, johnsongrass, Palmer amaranth, and prickly sida plus two others, barnyardgrass and common cocklebur, as benchmark species. Each weed was planted into peanut uniformly at eight weeds/10 m of row. Dry weed biomass accounted for 77 to 90% of variation in in-shell peanut yield loss; however, model parameters only allow for weed number. Yield losses from these experiments were compared to those predicted by the model to test original CI accuracy. Treatment means were compared to the prediction model with the use of protected LSD. Several significant differences were noted, and the CIs for those weed species were adjusted accordingly. Adjusting CIs improved actual yield data goodness of fit to model predictions specific to environment in question, but not necessarily in different environments. The CI changed at Ft. Cobb were eclipta from 1.8 to 4.5 and ivyleaf morningglory from 3.4 to 5.0. CI adjustments at Perkins were common cocklebur from 10.0 to 5.8 and johnsongrass from 3.0 to 4.6. Collecting data for several weed species at uniform density in a crop provides a more time-efficient method for obtaining accurate relative weed interference data; this method is useful in validating or establishing CI lists in areas and/or crops with limited data.

The response of the sugarcane cultivars HoCP 91-555, HoCP 85-845, and LCP 85-384 to flumioxazin during the first (plant cane) and second (first ratoon) production years was evaluated within two identical experiments, the first starting in 2000 and the second in 2001. In the plant-cane crop, flumioxazin application timings were PRE immediately following planting, fall postemergence (FPOST) 6 wk after planting, early spring postemergence (ESPOST), postemergence-directed spray (PDS) following layby cultivation, and sequential applications of FPOST followed by ESPOST. During the first-ratoon crop, flumioxazin was applied ESPOST, late-spring (LSPOST), PDS following layby cultivation, and sequentially LSPOST followed by PDS. Flumioxazin injury to sugarcane consisted mainly of stunted growth and reddening and necrosis of treated leaves. In plant cane, injury was 28% 2 wk after treatment (WAT) when applied ESPOST in one experiment but less than 10% in the other, and was no more than 13% in either experiment at 6 WAT. In the first-ratoon crop, injury was around 15% when applied ESPOST in the first experiment, but no injury was observed 6 WAT. However, in the first ratoon, injury to all cultivars was 25 to 30% when following a LSPOST application. When applied as a PDS, injury was no more than 15% 4 WAT in either plant-cane or first-ratoon sugarcane. Stalk height was reduced 15 cm compared to the nontreated control when flumioxazin was applied as a sequential application (FPOST followed by ESPOST) in plant cane and by 23 cm (LSPOST followed by PDS) in first-ratoon sugarcane. In plant cane ESPOST applications of flumioxazin reduced sugar yield (9 to 28%) within all three cultivars used in this study in both experiments with only one exception. Sequential (FPOST followed by ESPOST) applications reduced sugar yield within all cultivars (6 to 37%). PDS applications at layby reduced yields (7 to 12%) in the first experiment, but not in the second experiment. In the first-ratoon crop, LSPOST applications of flumioxazin reduced sugar yield (7 to 11%), sequential flumioxazin applications (LSPOST followed by PDS) reduced sugar yields (8 to 19%), and PDS applications at layby did not reduce yield. It appears that there is little if any difference in tolerance to flumioxazin for the cultivars used in this experiment. To avoid risk of yield loss, flumioxazin should not be applied as an over-top POST treatment to weeds in actively growing sugarcane, and care should be taken to minimize spray contact with sugarcane leaves when applying flumioxazin as a PDS at layby.

Studies were conducted for 12 wk from June 16 to September 8, 2003 and July 10 to October 4, 2004 with the objective of evaluating growth regulation, lateral regrowth, and injury of Tifway bermudagrass [Cynodon dactylon (L.) × C. transvaalensis Burtt-Davy Tifway] in response to two GA-inhibiting plant growth regulators, trinexapac-ethyl and flurprimidol. Trinexapac-ethyl was applied alone at 0, 0.052, and 0.104 kg ai/ha and flurprimidol alone at 0, 0.14, and 0.28 kg ai/ ha, plus all combinations. Applications were made every 3 wk for the duration of the study. Tifway bermudagrass clipping yield was reduced 33% and 54% by trinexapac-ethyl at 0.104 kg/ha at 4 and 8 wk after initial treatment (WAIT), respectively. Flurprimidol at 0.28 kg/ha reduced clipping yield 49% 8 WAIT. Lateral regrowth was reduced 20% 2 WAIT by trinexapac-ethyl at 0.104 kg/ha, and 26% 2 WAIT by flurprimidol at 0.28 kg/ha. Lateral regrowth was reduced 13% 4 WAIT by trinexapac-ethyl at 0.104 kg/ha, and 15% 4 WAIT by flurprimidol at 0.28 kg/ha. Overall, acceptable injury (<30%) was observed with a trinexapac-ethyl and flurprimidol tank mixture; however, this evaluation did not indicate an advantage in growth regulation when using a tank mixture of these products, compared to using them alone.

The potential for future commercialization of glyphosate-resistant wheat necessitates evaluation of agronomic merits of this technology. Experiments were established to evaluate glyphosate-resistant wheat and weed responses to glyphosate rate, application timing, and tank mixtures. Glyphosate at 1,680 g/ha did not injure wheat. Wheat response to glyphosate applied to one- to three- or three- to five-leaf wheat was not different from that of untreated wheat. Wheat was injured more from glyphosate plus thifensulfuron or glyphosate plus dicamba than from individual herbicides at one of six locations, but grain yield was not affected by glyphosate tank mixtures. Glyphosate application timing did not affect control of wild oat or common lambsquarters 56 d after treatment. Glyphosate when applied to one- to three-leaf wheat provided better control of wild buckwheat than later glyphosate application, whereas glyphosate applied to three- to five-leaf wheat provided the best control of green and yellow foxtail, redroot pigweed, and Canada thistle. Weed control with glyphosate tended to be better than with conventional herbicides, and wheat treated with glyphosate produced approximately 10% more grain than wheat treated with conventional herbicide tank mixes.

During routine use of fluazifop-P-butyl for grass control, county extension agents in Georgia observed control of bristly starbur in grower fields. Experiments to characterize the activity of fluazifop-P-butyl on bristly starbur were conducted under greenhouse conditions in Gainesville, FL, during 2001 and 2002. Fluazifop-P-butyl activity was characterized as a function of herbicide rate and time after application. Commercially available fluazifop-P-butyl was compared to technical fluazifop-P-butyl as a function of herbicide rate and bristly starbur height. Finally, injury to bristly starbur was evaluated when clethodim, diclofop, fluazifop-P-butyl, haloxyfop, quizalofop-p, and sethoxydim were applied at two growth stages. Fluazifop-P-butyl caused >90% injury to bristly starbur with all other post graminicides displaying <8% injury. Nonlinear regression revealed a sigmoidal response of bristly starbur injury to fluazifop-P-butyl. Estimates for 50 and 90% bristly starbur injury (I50 and I90) were 0.07 and 0.14 kg ai/ha, respectively. There was no difference in activity of technical and commercial fluazifop-P-butyl formulations. There was a differential response of bristly starbur to fluazifop-P-butyl over time as a function of plant height at the time of treatment. However, 14 days after treatment (DAT) all treatments displayed >89% injury. Bristly starbur response to fluazifop-P-butyl was similar to injury associated with contact-type herbicides.

Studies were conducted in 2002 and 2003 on a golf course fairway in New Jersey to compare spring, summer, and fall treatments of bispyribac-sodium for annual bluegrass control and creeping bentgrass tolerance. Single applications at 74, 111, or 148 g ai/ha were applied in May, August, or October. Split applications of 37 followed by (fb) 37 or 74 fb 74 g/ha applied 3 wk apart were also evaluated. Summer-applied bispyribac-sodium did not reduce bentgrass quality, whereas spring and fall treatments reduced turf quality at 3 wk after treatment and fall treatments in 2002 substantially reduced bentgrass quality. Summer treatments were more effective than spring or fall treatments in reducing annual bluegrass cover. Final evaluations revealed 36, 31, 21, and 26% annual bluegrass cover averaged across nontreated, spring-treated, summer-treated, and fall-treated plots, respectively. This study demonstrates that two split applications of bispyribac-sodium at 74 g/ha in summer can effectively reduce annual bluegrass cover while minimizing creeping bentgrass injury.

Bispyribac-sodium is a POST herbicide that selectively controls annual bluegrass in creeping bentgrass, but inconsistent results with seasonal applications are believed to occur from temperature influences on bispyribac-sodium efficacy. Growth chamber experiments at the New Jersey Experimental Greenhouse Research Complex, New Brunswick, NJ, investigated three temperature regimes on ‘L-93’ creeping bentgrass and annual bluegrass responses to bispyribac-sodium. Annual bluegrass and creeping bentgrass exhibited contrasting responses to bispyribac-sodium as temperature increased from 10 to 30 C. Regressions of 4 week after treatment (WAT) data revealed as temperature increased from 10 to 30 C, required bispyribac-sodium rates for 50% clipping reduction (CR50) of annual bluegrass decreased from 85 to 31 g ai/ha and required rates for 50% leaf chlorosis decreased from greater than 296 to 98, indicating increased herbicidal efficacy at higher temperatures. In contrast, required bispyribac-sodium rates for creeping bentgrass CR50 increased from 200 to greater than 296 as temperature increased from 10 to 30 C. Bispyribac-sodium discolored creeping bentgrass 0 to 20% at 20 and 30 C and discoloration increased 10 to 50% at 10 C. Thus, warmer temperatures (20 and 30 C) increase bispyribac-sodium efficacy for annual bluegrass control with minimal bentgrass discoloration; however, cooler temperatures (10 C) have minimal efficacy on annual bluegrass and increase bentgrass chlorosis.

Substantial weed growth often occurs in legume-cereal cover-crop mixes commonly grown on organic vegetable farms. A 2-yr study at the USDA-ARS in Salinas, CA, was conducted to test the effect of zero, one, and two passes with a rotary hoe on weed control in a mixed cover crop of 10% rye, 15% common vetch, 15% purple vetch, 25% peas, and 35% bell bean. Rotary hoeing occurred 14–15 days after planting (DAP) in the one-pass treatment, and 14 and 28 DAP in the two-pass treatment. Rotary hoeing did not affect total cover-crop density or biomass in either year, but reduced rye density and biomass in year 2. One pass reduced total weed density by 69% in year 1 and 49% in year 2. A second pass did not affect weed density in year 1 but reduced weed density an additional 33% in year 2. One pass decreased weed biomass in year 1, whereas two passes were required to reduce weed biomass in year 2. Rotary hoeing reduced seed shed by chickweed and shepherd's-purse seeds, the two predominant weed species, by 80 to 95% in both years. Rotary hoe efficacy depended on weather conditions directly before and after cultivation. The decision to repeat rotary hoeing should be based upon field scouting and weather conditions following the initial pass with the rotary hoe.

Field studies were conducted to evaluate rice injury and control of propanil-resistant and -susceptible (natural infestation) barnyardgrass, broadleaf signalgrass, and Amazon sprangletop with BAS 625, cyhalofop, and fenoxaprop plus the safener isoxadifen in rice. BAS 625 at 100 g ai/ha applied to two- to three-leaf rice resulted in 19 to 72% injury in three of four experiments. Fenoxaprop plus isoxadifen at 90 + 98 g ai/ha injured rice 11 to 31%, and cyhalofop at 280 g ai/ha consistently resulted in minimal rice injury. The most effective control (84 to 99%) of propanil-resistant and propanil-susceptible barnyardgrass across all experiments was achieved with sequential applications of the BAS 625 at 75 and 100 g ai/ha, cyhalofop at 210 and 280 g ai/ha, and fenoxaprop plus isoxadifen at 68 + 74 and 90 + 98 g ai/ha. When the graminicides were applied to four- to six-leaf rice (one tiller), propanil-resistant and propanil-susceptible barnyardgrass control was generally very poor. Fenoxaprop plus isoxadifen controlled broadleaf signalgrass 91 to 100%, even when applied once to four- to six-leaf rice. BAS 625 at 75 and 100 g ai/ha and cyhalofop at 210 and 280 g ai/ha applied sequentially provided consistent broadleaf signalgrass control (≥98%). Amazon sprangletop control was good (85 to 99%) with fenoxaprop plus isoxadifen at 45 + 49, 68 + 74, and 90 + 98 g ai/ha (applied in a single application or sequentially), BAS 625 at 100 g ai/ha applied to two- to three-leaf and four- to six-leaf rice or 50, 75, and 100 g ai/ha applied sequentially, and cyhalofop at 140, 210, and 280 g ai/ha applied to two- to three-leaf rice or sequentially.

Texas wheat producers have observed reduced efficacy and failure to control Italian ryegrass with registered rates of sulfonylurea herbicides that were previously effective. Growth chamber studies were conducted to quantify the sensitivity and distribution of Italian ryegrass ecotypes in Texas to triasulfuron and to determine alternative herbicide management options. Italian ryegrass seed samples were collected from over 40 wheat fields in 13 central and north Texas counties where declining Italian ryegrass control was reported by farmers following sulfonylurea herbicide application(s). Two-leaf Italian ryegrass was screened with an application of 150 g ai/ha triasulfuron, a rate five times the registered herbicide use rate. Sensitivity was determined by the response of an ecotype to that of a known susceptible population. Of the 48 Italian ryegrass ecotypes sampled, nine were comparable to susceptible standard, while the remaining 39 ecotypes were less sensitive to triasulfuron. Four of the least sensitive ecotypes to triasulfuron plus the susceptible standard were selected for a subsequent study. Diclofop, clodinafop, and metribuzin reduced fresh weights by at least 69, 71, and 62% across all ecotypes. No imazamox or triasulfuron treatment reduced fresh weights more than 60%.

Corn and soybean growers across Indiana were surveyed in 2003 to determine their perceptions of the importance of weed problems in various crop rotations. Growers were asked to list the three most problematic weeds in the following rotation systems: soybean and corn planted in alternate years (SC) and corn (CC) or soybean (SS) planted to the same field for 2 or more years. Although some summer annuals and perennials (common lambsquarters, Canada thistle, and common cocklebur) and winter annuals (chickweed and henbit) were considered problematic by at least 10% of growers in all three systems, there were differences among systems in the relative importance of weed species. Giant ragweed was considered problematic by at least 30% of SC and CC growers but by less than 10% of SS growers. Horseweed was listed as a problematic summer annual by 13% of SS growers but by only 3% of CC growers. Purple deadnettle was listed by 15% of CC growers but by less than 6% of SC and SS growers. Perennial dicots were more problematic in SS than in CC. Annual and perennial grasses were more problematic in CC than in SC or SS. Despite these differences, the results of this survey suggest that the cumulative effect of weed management practices in corn and soybean rotation systems in Indiana has been the promotion of larger seeded, broadleaf, summer annual species.

Agronomic research and extension personnel generally recognize the benefits of integrated pest management (IPM) but IPM practices have not been rapidly adopted by farmers. In order for applied research and extension programs to be as influential as possible, strategies and tactics must be evaluated in the context of the real-world constraints experienced by farmers. We investigated the linkage between farmers' pest management behaviors, attitudes, and constraints by analyzing an extensive corn pest management survey distributed throughout Wisconsin in 2002. Our objectives were to (1) create a benchmark against which future changes in pest management practices could be detected and (2) explore potential associations between practices and farm characteristics, e.g., farm size or commodity produced. A total of 213 farmers responded with descriptions of their operations; weed, insect, and disease pest management practices; crop consultant usage; interactions with their local agrichemical dealer; and attitudes regarding pest management decision-making. We compared the relative responses of cash-grain and dairy farmers as well as managers of large and small farms. Larger farm size and percentage of operation in cash-grain production were associated with an increased frequency of rotating crops, rotating herbicide families, and use of a broadcast herbicide application. Managers of large farms and/or cash-grain crops also more frequently indicated considering the level of pest control, price, carryover potential, weed resistance management, environmental safety, and risk to the applicator than did dairy or small-sized operations. Cash-grain farmers had significantly higher scores on a calculated IPM index than did dairy farmers (P < 0.0001). We also found a significant positive relationship between farm size and IPM score (P < 0.0001). Our results provide a benchmark for future comparisons of IPM adoption rates in Wisconsin and highlight the association between IPM research/extension and farmers' management behavior.

Corn and soybean growers across Indiana were surveyed during winter 2003/2004 to assess their perceptions about the importance of glyphosate-resistant weeds and management tactics to prevent development of resistant populations. The survey showed two intriguing observations. First, 65% of survey respondents expressed moderate or low levels of concern about weeds developing resistance to glyphosate, whereas 36% expressed a high level of concern. Second, when asked an open-ended question regarding the factors that contribute to development of glyphosate-resistant weeds, 58% of the responses included repeated use of the same mode of action. Other factors such as poor application techniques or timing (33%), unique weed characteristics (8%) and changes in tillage practices (1%) were also mentioned. The survey showed that even though a relatively low percentage of respondents were highly concerned about resistance, they still expressed a willingness to use field scouting, tank-mix partners with glyphosate for burn-down and postemergence weed control, and soil-applied residual herbicides as resistance management strategies. This survey also showed that growers who farm 800 ha or more were more concerned about glyphosate resistance and more likely to adopt resistance management strategies than smaller growers.

Chinese yam is an exotic perennial vine that invades natural areas in the temperate regions of the eastern United States. Research was conducted from 2001 to 2004 to evaluate growth, reproduction, and management options for this weed. Vine length, lateral shoot production, and reproductive capacity were lower in the first year of growth compared to 2 subsequent years. During the second and third growing season, plants were more mature and tended to flower earlier and produce larger bulbils compared to the first growing season. Maximum vine length was not reached prior to frost in the first year and was approximately 480 cm in each of the subsequent years. Both glyphosate and triclopyr were effective in controlling plants growing from bulbils and plants growing from tubers. Triclopyr did not display acropetal translocation, in that only the treated tissue died. However, both products displayed excellent basipetal translocation resulting in elimination of tubers and no shoot regrowth the year following treatment. Native area managers should attempt to eradicate small populations of Chinese yam prior to establishment of an extensive tuber system.

Greenhouse, growth chamber, and winter survival studies were conducted at Stoneville, MS from 1996 to 2002 to determine growth, time to first flower, and winter survival of wetland nightshade. At 12 wk after emergence, wetland nightshade plants had 58-, 45-, 48-, and 4-cm heights, respectively; 24, 21, 21, and 12 nodes/plant, respectively; 62, 31, 36, and 21 leaves/plant, respectively; and 7.1, 3.9, 5.1, and 0.3 g/plant dry weights, respectively, at temperatures of 26/36, 20/30, 14/24, and 8/18 (±0.5) C at the 14/10 day/night length. Flowering occurred at 79, 85, and 85 days after emergence at 26/36, 20/30, and 14/24 C night/day, respectively at the 14/10 day/night cycle. Wetland nightshade plants did not flower at 8/18 C. Wetland nightshade growth was adequate for flowering and fruit production in additional areas of the southeastern United States with night/day temperatures greater than or equal to 14/24 C. Winter survival was greater than or equal to 33% for established wetland nightshade plants in 5 of 6(1996 to 2002) above water levels and 82% from 20 cm below the water surface. Based on these results, wetland nightshade has the potential to continue to spread in the United States.

Cogongrass is a serious weed in small-scale farms in the lowland humid zone of West Africa. This study evaluated the response of cogongrass to herbicides and the legume cover crop velvetbean in cassava and white Guinea yam. In 2001/2002, cassava tuber yields and gross returns in treatments that received glyphosate alone were higher than in plots that received fluazifop-P-butyl once. In 2002/2003, treatments that received fluazifop-P-butyl once, glyphosate alone, glyphosate integrated with sowing velvetbean, or hoeing only, had higher cassava tuber yields than other treatments. Gross returns were higher in treatments that received glyphosate followed by sowing velvetbean or those hoed only than in other treatments. Fluazifop-P-butyl applied twice, glyphosate alone, or glyphosate followed by sowing velvetbean reduced cogongrass shoot biomass more than other treatments. Rhizome biomass was lower in plots that received glyphosate alone than in all fluazifop-P-butyl treatments. In 2002, white Guinea yam tuber yields were highest in plots that received glyphosate alone and lowest in plots where fluazifop-P-butyl was applied alone or followed by sowing velvetbean. The highest gross return was obtained in plots that received glyphosate alone while the lowest was obtained in plots that received fluazifop-P-butyl once followed by sowing velvetbean. In 2003, the highest tuber yields and gross returns were from plots that received glyphosate alone, fluazifop-P-butyl alone, or those hoed only. The hoed-only plots had 14 times higher cogongrass shoot biomass and 7 times higher rhizome biomass than other treatments. In both crops, hoeing alone or followed by sowing velvetbean was more costly than chemical control. The highest margin over hoeing was obtained from plots that received glyphosate alone. Sensitivity analysis showed that using glyphosate was more cost effective than fluazifop-P-butyl, even if the cost of the herbicide increased by 100% or the cost of labor decreased by 30%.

In input-intensive cropping systems around the world, farmers rarely proactively manage weeds to prevent or delay the selection for herbicide resistance. Farmers usually increase the adoption of integrated weed management practices only after herbicide resistance has evolved, although herbicides continue to be the dominant method of weed control. Intergroup herbicide resistance in various weed species has been the main impetus for changes in management practices and adoption of cropping systems that reduce selection for resistance. The effectiveness and adoption of herbicide and nonherbicide tactics and practices for the proactive and reactive management of herbicide-resistant (HR) weeds are reviewed. Herbicide tactics include sequences and rotations, mixtures, application rates, site-specific application, and use of HR crops. Nonherbicide weed-management practices or nonselective herbicides applied preplant or in crop, integrated with less-frequent selective herbicide use in diversified cropping systems, have mitigated the evolution, spread, and economic impact of HR weeds.

Feral rye, commonly referred to as cereal, winter, common, or volunteer rye, is an important weed in winter wheat production in many parts of the United States and the world. Feral rye reduces net profits in the United States by more than $27 million due to lower grain yields, increased dockage, and reduced land values. To date, limited research has been conducted on components that make feral rye a problem in various cropping systems. Herbicide-tolerant wheat technology can be used to manage feral rye, but current efficacy levels are not adequate for high feral rye densities. In addition, the long-term effects that individual management strategies may have on feral rye populations are unknown. This review addresses the physical, environmental, and genetic characteristics of Secale cereale. Current economic impact, management, and research data gaps are also discussed.