Prostrate water primrose is a troublesome weed in rice paddy fields. A study was conducted to determine the influence of environmental and agronomic factors on its emergence. The efficacy of herbicides on this species was also examined. The germination percentage of mature seeds remained above 90% within 180 d after harvest, indicating a low primary dormancy of this species. Light stimulated seed germination. Seeds buried deeper than 0.5 cm did not form seedlings. These results suggest that stale seedbed practices and deep tillage operations can mitigate the occurrence of this species in paddy fields. The optimum temperature for germination varied from 25/15 C to 35/25 C. The osmotic potential and salt concentration needed to inhibit 50% of maximum germination were −0.4 MPa and 197 mM, respectively. Seeds were tolerant to flooding and did not germinate at pH 8 to 10. The preemergence herbicides oxadiazon, oxadiargyl, and butachlor had excellent control efficacy on prostrate water primrose, with a 95.4% to 100% reduction in seedling number and a 99.2% to 100% reduction in biomass, respectively. The postemergence herbicides MCPA-Na + bentazone, bentazone, MCPA-Na, and fluroxypyr applied at the 2- to 3-leaf stage of prostrate water primrose provided a 90.6% to 100% reduction in seedling number and a 99.3% to 100% reduction in biomass. The results of this study can help in developing sustainable and effective integrated weed management strategies for controlling prostrate water primrose in paddy fields.

In recent years, soybean acreage has increased significantly in western Canada. One of the challenges associated with growing soybean in western Canada is the control of volunteer glyphosate-resistant (GR) canola, because most soybean cultivars are also glyphosate resistant. The objective of this research was to determine the impact of soybean seeding rate and planting date on competition with volunteer canola. We also attempted to determine how high seeding rate could be raised while still being economically feasible for producers. Soybean was seeded at five different seeding rates (targeted 10, 20, 40, 80, and 160 plants m−2) and three planting dates (targeted mid-May, late May, and early June) at four sites across western Canada in 2014 and 2015. Soybean yield consistently increased with higher seeding rates, whereas volunteer canola biomass decreased. Planting date generally produced variable results across site-years. An economic analysis determined that the optimal rate was 40 to 60 plants m−2, depending on market price, and the optimal planting date range was from May 20 to June 1.

This study aimed to evaluate the effects of toxic baits and attractants for fruit flies on the biology of its parasitoid Fopius arisanus. We tested two food-based attractants; hydrolysed corn protein (Biofruit® 3%) and sugarcane molasses (7%), their mixtures with spinosad and malathion-based insecticides, and a ready-to-use commercial bait (Success 0.02 CB®). Malathion-based lures were used as references for mortality (i.e., positive control), while negative control was honey. The formulations Biofruit® + malathion (T1), molasses + malathion (T2), and spinosad + molasses (T3) were toxic to F. arisanus, being classified as harmful (class 4). In addition, toxic baits composed of Biofruit + spinosad (T4) reduced parasitism by 97.99%, being rated as moderately harmful (class 3). Yet, Success 0.02 CB® (T7) was considered slightly toxic (class 2), causing a 64.55% reduction in parasitism. Regarding the biological parameters of F. arisanus, offspring number and parasitoid longevity were significantly reduced by using hydrolysed protein attractants when compared to the control (honey). However, sugarcane molasses improved parasitoid reproduction and longevity, as did the honey. Lastly, ingestion tests showed the major role of attractants in toxic-bait formulations against F. arisanus.

Glyphosate-resistant (GR) horseweed is one of the most common and troublesome weeds in soybean production fields in several states in the United States, including Nebraska. The evolution of horseweed resistant to several herbicide sites of action has prioritized an integrated approach, including tillage, for effective management of this problem weed. The objectives of this study were to evaluate the effect of tillage or herbicide applied in fall or spring followed by a PRE, POST, and PRE followed by a POST herbicide program for GR horseweed control as well as GR soybean injury and yield in Nebraska. Field studies were established in the fall 2014–2015 and 2015–2016 growing seasons using a factorial randomized complete block design with shallow tillage or herbicide applied at different timings as two factors. Shallow tillage was accomplished using a 50-cm-wide rototiller operated at a depth of 10 cm. At soybean harvest, tillage applied the previous year in fall or spring without any follow-up herbicide treatment provided 79% to 88% horseweed control compared with 27% and 56% control with 2,4-D plus carfentrazone applied in fall and spring, respectively. Tillage or herbicide applied in fall or spring followed by a PRE, POST, or PRE and POST herbicide provided 82% to 99% GR horseweed control at soybean harvest. Soybean yield in this study was similar in most treatments. Tillage or herbicide applied in fall or spring provided similar horseweed control and soybean yield when followed by a PRE, POST, or PRE and POST herbicide; therefore, fall- or spring-applied herbicides can be rotated with shallow tillage for integrated season-long horseweed management.

Information about weed biology and weed population dynamics is critical for the development of efficient weed management programs. A field experiment was conducted in Fayetteville, AR, during 2014 and 2015 to examine the effects of Palmer amaranth (Amaranthus palmeri S. Watson) establishment time in relation to soybean [Glycine max (L.) Merr.] emergence and the effects of A. palmeri distance from the soybean row on the weed’s height, biomass, seed production, and flowering time and on soybean yield. The establishment time factor, in weeks after crop emergence (WAE), was composed of six treatment levels (0, 1, 2, 4, 6, and 8 WAE), whereas the distance from the crop consisted of three treatment levels (0, 24, and 48 cm). Differences in A. palmeri biomass and seed production averaged across distance from the crop were found at 0 and 1 WAE in both years. Establishment time had a significant effect on A. palmeri seed production through greater biomass production and height increases at earlier dates. Amaranthus palmeri that was established with the crop (0 WAE) overtopped soybean at about 7 and 10 WAE in 2014 and 2015, respectively. Distance from the crop affected A. palmeri height, biomass, and seed production. The greater the distance from the crop, the higher A. palmeri height, biomass, and seed production at 0 and 1 WAE compared with other dates (i.e., 2, 4, 6, and 8 WAE). Amaranthus palmeri establishment time had a significant impact on soybean yield, but distance from the crop did not. The earlier A. palmeri interfered with soybean (0 and 1 WAE), the greater the crop yield reduction; after that period no significant yield reductions were recorded compared with the rest of the weed establishment times. Knowledge of A. palmeri response, especially at early stages of its life cycle, is important for designing efficient weed management strategies and cropping systems that can enhance crop competitiveness. Control of A. palmeri within the first week after crop emergence or reduced distance between crop and weed are important factors for an effective implementation of weed management measures against A. palmeri and reduced soybean yield losses due to weed interference.

Field bindweed (Convolvulus arvensis L.) is a persistent, perennial weed species that infests a variety of temperate habitats around the globe. To evaluate the efficacy of general management approaches and impacts on crop yield and to identify research gaps, we conducted a series of meta-analyses using published studies focusing on C. arvensis management in annual cropping and perennial systems. Our analysis of 48 articles (560 data points) conducted in annual systems indicated that 95% of data points measured efficacy over short time frames (within 2 yr of treatment). Furthermore, only 27% of data points reported impacts of C. arvensis management on crop yield. In annual systems, herbicide control dominated the literature (~80% of data points) and was an effective management technique up to 2 yr posttreatment. Integrated management, with or without herbicides, and three nonchemical techniques were similarly effective as herbicide at reducing C. arvensis up to 2 yr posttreatment. In addition, integrated approaches, with or without herbicides, and two nonchemical techniques had positive effects on crop yield. There were few differences among herbicide mechanism of action groups on C. arvensis abundance in annual systems. There were only nine articles (28 data points) concerning C. arvensis management in perennial systems (e.g., pasture, rangeland, lawn), indicating more research effort has been directed toward annual systems. In perennial systems, biocontrol, herbicide, and non-herbicide integrated management techniques were equally effective at reducing C. arvensis, while competition and grazing were not effective. Overall, our results demonstrate that while chemical control of C. arvensis is generally effective and well studied, integrated and nonchemical control practices can perform equally well. We also documented the need for improved monitoring of the efficacy of management practices over longer time frames and including effects on desired vegetation to develop sustainable weed management programs.

The Spurgia esulae gall midge was introduced in North Dakota in 1986 as a biocontrol agent for leafy spurge. Spurgia esulae causes stem tip galls thereby decreasing seed production and it has been most successful near wooded areas. However, a second control method is needed to reduce the leafy spurge infestation and prevent spread from roots. Imazethapyr, 2,4-D, or picloram application did reduce the number of S. esulae galls but not the number of larvae per gall. Long-term S. esulae population was not affected by herbicide application. The integration of herbicides with S. esulae would prevent leaf spurge spread from a wooded area and would reduce seed production within an area where herbicides generally cannot be used.

Cogongrass is a weed throughout the tropics and subtropics. Introductions early this century have spread into forests, rangelands, reclaimed mined areas, roadsides, and natural ecosystems in the southeastern United States. Vegetative reproduction is the primary mechanism for survival and local spread, and sexually produced seeds of this obligate outcrossing species provide natural long-distance dispersal. Highly germinable (≥ 90%) seeds have no dormancy, though spikelet fill may be low (≤ 40%) in natural populations. Early seedling establishment, prior to rhizome development, is low (< 20%), occurring in areas with little competition; ≥ 75% bahiagrass sod cover is required to prevent cogongrass seedling establishment. Imazapyr and glyphosate are the most effective herbicides for cogongrass control. Younger cogongrass shoots are very susceptible to these herbicides; however, longer term control of adult plants requires translocation and thereby control of the rhizomes. Autumn applications of glyphosate and imazapyr provided greatest suppression of rhizome regrowth. Effective cogongrass management options exist and depend on integrating several control strategies. Mechanical control alone provides short-term control, whereas multiple discings plus herbicide application provide longer term control. Some combinations of herbicide, discing, and revegetation with desirable plant species provide excellent control. Because of the large geographic area infested with cogongrass and the often economically and environmentally unacceptable management techniques, biological control organisms also should be researched.

Angora goats have been suggested as biological control agents for leafy spurge, especially in environmentally sensitive or limited access areas. Dietary preferences and dietary nutritive content of herded Angora goats were evaluated over a two-year period in North Dakota. Relative preferences of forages were evaluated by comparing botanical composition of diets as determined by microhistological analysis of fecal samples to forage availability in the field. Leafy spurge and shrubs comprised the largest percentage of goat diets throughout each grazing season. Goats preferred leafy spurge and shrubs at all times and avoided most cool-season grass species. The nutritional requirements of Angora goats nursing kids were met throughout the grazing season. Use of Angora goats is another tool available to land managers to manage leafy spurge infestations in the Northern Plains.

Itchgrass is an aggressive weed species in tropical agroecosystems. Because of phytosanitary restrictions to exports, pineapple producers must use a zero tolerance level for this species. An understanding of itchgrass seedling emergence would help producers to better time POST control. The objective of the present study was to characterize itchgrass seedling emergence patterns and develop a predictive model. Multiple field experiments were conducted in four agricultural fields in Costa Rica between 2010 and 2011 for a total of 9 site-years. Itchgrass consistently showed a biphasic emergence pattern, with a first emergence phase that was faster and more consistent across site-years than the second one. Weibull + logistic models based on chronological time (R2adj = 0.92) and thermal time with Tbase = 20 C (R2adj = 0.92) provided the best fit for the combined emergence data for two experimental locations in 2010. Both models predicted itchgrass seedling emergence adequately for most site-years, but the thermal-time model was more accurate (R2adj = 0.64 to 0.86) than the chronological model (R2adj = 0.31 to 0.74), especially when temperatures were high. Both models showed high accuracy in the first emergence phase but tended to underestimate emergence rate during the second phase. The models predicted 50% emergence at 14 d or 80 growing degree days and the stabilization of the first emergence phase at approximately 25 d or 200 growing degree days. Thus, these models can be used to properly time itchgrass POST control. More research is needed to understand the regulatory mechanisms responsible for the variability of the second emergence phase.

Experiments were conducted in subirrigated and upland Colorado pastures to compare herbicides applied alone in fall to the same herbicides preceded by one, two, or three mowings. Picloram controlled Canada thistle (Cirsium arvense) well at both sites, and in general, mowing did not improve its performance. Picloram at 560 g ai/ha and picloram plus 2,4-D at 280 plus 1,120 g ai/ha were the lowest rates that eliminated Canada thistle. Mowing did not improve chlorsulfuron performance at either site, but chlorsulfuron eliminated Canada thistle at the subirrigated site. Dicamba controlled 97% of Canada thistle at the subirrigated site, and mowing did not improve its performance; two or three mowings before spraying dicamba at the upland site improved performance, but 37% remained uncontrolled. Control from the reduced rate and the two lowest recommended rates of clopyralid plus 2,4-D was improved by two or three prior mowings at the subirrigated site, but only the highest rate benefited from two or three mowings at the upland site. Mowing alone three times per year for 2 yr controlled 85% of Canada thistle at the subirrigated site, but failed to control it at the upland site. Variability in results between experiments likely was due to a high water table at the subirrigated site, which may have restricted Canada thistle root growth and possibly made it easier to control. Inconsistent results prohibit concluding that mowing before spraying will consistently improve Canada thistle control, and such a treatment combination should not be commonly recommended.

Weed scientists are facing research problems, such as invasive weeds, that may require multidisciplinary approaches to solve. One example is jointed goatgrass, a winter annual grass invading winter wheat fields and not easily managed with conventional control tactics. A national research program was started in 1994 to develop jointed goatgrass management strategies. Involving more than 35 scientists with diverse scientific expertise, this national approach fostered cooperative research projects across 11 states. Research involved entomology, economics, plant breeding, plant physiology, genetics, and weed science, leading to successful management systems for jointed goatgrass. To help other scientists organize regional or national programs, we describe development and performance of the jointed goatgrass program as well as suggest ideas for possible improvement. Pivotal to the success of the program was a Steering Committee, whose role was to establish research priorities and coordinate research across the western United States.

Yellow starthistle is an aggressive annual forb that has invaded millions of hectares of California's annual range. Control efforts such as burning and herbicides have been effective for short-term management. However, recruitment from the seedbank or reinvasion of the annual grassland system results in a rapid return to yellow starthistle dominance. Establishing perennial grasses would be ideal for suppression of yellow starthistle. However, a lack of effective weed control options in California during a seeding program has limited perennial grass establishment. Clopyralid was used to control yellow starthistle annually for 1, 2, or 3 yr to provide a window of reduced competition for pubescent wheatgrass establishment. Total plant cover, yellow starthistle density, biomass, and seedhead number were quantified for 6 yr. Clopyralid treatment significantly reduced yellow starthistle and allowed pubescent wheatgrass establishment with a single treatment. Both clopyralid treatment and pubescent wheatgrass establishment significantly affected the range plant community composition. Annual grasses and forbs increased in plots only treated with clopyralid for 2 or 3 yr, whereas clopyralid-treated pubescent wheatgrass plots maintained lower annual grass and forb cover. Integrating pubescent wheatgrass seeding with clopyralid treatment provided long-term yellow starthistle suppression, whereas clopyralid treatment alone resulted in a plant community susceptible to repeated invasion. These findings support the establishment of competitive perennial grasses in annual grasslands as an important component of long-term yellow starthistle management.

Jointed goatgrass is a prominent weed infesting winter wheat in the western United States. Individual control tactics often are ineffective and inconsistent, but management systems comprised of several tactics designed to disrupt population dynamics of jointed goatgrass can reduce infestation levels in winter wheat. Tactics are planned to favor decline of seedbank density, reduce seedling emergence in winter wheat, and minimize seed production of plants established in winter wheat. We describe a visual guide that will help producers plan management systems for jointed goatgrass with a diversity of cultural tactics. The guide organizes cultural tactics by decision times of producers during the winter wheat production cycle. Scientists are effectively managing jointed goatgrass in a diversity of production systems by integrating cultural tactics across decision times.

In little over 20 yr, Palmer amaranth has risen from relative obscurity to its current status as one of the most widespread, troublesome, and economically damaging agronomic weeds in the southeastern U.S. Numerous factors have enabled Palmer amaranth to become such a dominant and difficult-to-control weed, including its rapid growth rate, high fecundity, genetic diversity, ability to tolerate adverse conditions, and its facility for evolving herbicide resistance. It is both a serious threat to several U.S. cropping systems and a fascinating model weed. In this paper, we review the growing body of literature on Palmer amaranth to summarize the current state of knowledge on the biology, agricultural impacts, and management of this weed, and we suggest future directions for research.

Current threshold-dominated methodologies of vulnerability analysis do not give sufficient emphasis to the processes that shape the environment and define the behaviour of environmental systems. While there has been widespread recognition for developing comprehensive approaches to assessing vulnerability, there has been relatively little theoretical debate on limitations and opportunities for improving the application of vulnerability analysis to environmental management, particularly in terms of a more complex systems perspective. A functional-based approach to ‘vulnerability’ is a means whereby the dynamics of vulnerable systems could be more fully integrated within vulnerability analysis. Functionality is seen as the ability of the environment to deliver outputs through time. Vulnerability analysis that is focused not only on thresholds that define the limits of system behaviour, but also on the process-defined capacity of systems to maintain this behaviour and deliver those outputs, could emerge as a useful element in integrated environmental management. Linking threshold analysis with a clear understanding of the interactions, differences and similarities between system processes which define coping ranges and system performance is a relatively simple conceptual development in vulnerability analysis. Such a development could, if successful, be of great value to those managing complex environments.

A review is provided of the status of integrated management technologies for the stemborers Busseola fusca and Chilo partellus in Lesotho. Busseola fusca is the most important stemborer of maize and sorghum while C. partellus is only important on sorghum. No stemborer-resistant maize or sorghum varieties are available and farmers mainly plant land races of these crops. Cultural control practices such as the use of crop residue management practices have potential in suppressing borer numbers. Chilo partellus numbers, especially, can be suppressed through the destruction of sorghum crop residues. Studies indicated that adaptation of planting date can lead to escape of damage and reduced yield losses. Surveys indicate that insecticide use is on the increase in Lesotho, but the efficacy of insecticides used for borer control is not always adequate. The most promising area for change towards a pest management system lies in crop residue management. Changing crop residue management practices, especially where sorghum residues are left in the fields, should be encouraged. There is a high likelihood of adoption of a system in which Napier grass is planted around maize fields since farmers place a premium on livestock feed. Development and adoption of an integrated pest management system will, however, only be successful if farmers are involved in its development.