With the spread of a new invasive plant species, it is vital to determine the effectiveness of removal strategies as well as their advantages and disadvantages before attempting widespread removal. While thousands of dollars have been spent to curtail the spread of wavyleaf basketgrass [Oplismenus undulatifolius (Ard.) P. Beauv.], a relatively new invasive species, the lack of a cohesive management plan and funding has made controlling this species especially difficult. We assessed the efficacy of a variety of chemical control methods and hand weeding for this species and followed select methods over time. We also assessed the potential for ecosystem recovery following removal by measuring total and native species richness in response to treatments. Our pilot study revealed a wide breadth of responses to our eight herbicides, with fluazifop plus fenoxaprop, imazapic, quizalofop, and sulfometuron methyl being the least effective. In our follow-up experiments, hand weeding, glyphosate, and clethodim treatments were effective at reducing O. undulatifolius percent cover, density, and biomass, with an average reduction of at least 48% in the first year. However, we found substantial variation in the effectiveness of clethodim between our two experiments, which was likely driven by site differences. We also found that all three of these removal methods were effective at reducing the number of O. undulatifolius flowering stems and the height of those stems, which will likely reduce the spread of this species to new areas. Finally, we found that these methods have the potential to restore total and native species richness, but that glyphosate-treated plots did not fully recover until 2 yr after treatment.

Weeds are among the main limitations on chickpea production in Iran. The efficacy of herbicide treatments including linuron PPI, imazethapyr PPI, PRE, and POST, pendimethalin PPI and POST, bentazon POST, pyridate POST, and oxadiazon POST along with one or two hand weedings were evaluated for weed control and yield response in rain-fed chickpea in Aleshtar, Lorestan, Iran in 2015 and 2016. Wild safflower, threehorn bedstraw, wild mustard, and hoary cress were the predominant weed species in both experimental years. Total weed dry biomass in weedy check plots averaged 187 and 238 g m−2 in 2015 and 2016, respectively, and weed density and biomass were reduced in all treatments compared to the weedy check in both years. Treatments composed of pyridate followed by one hand weeding or imazethapyr POST followed by two hand weedings resulted in the lowest weed biomass. The presence of weeds reduced yield by 74% and 66% in the weedy check plots compared to the weed-free control plots in 2015 and 2016, respectively. Application of oxadiazon, bentazon, and imazethapyr PPI, PRE, and POST resulted in lower chickpea yields. All herbicides tested injured chickpea slightly, with pyridate causing the least injury.

Weed removal experiments in dry edible beans were conducted during 1992 and 1993 at Crookston and Staples, MN. Ten manual weed removal treatments were studied to determine when a natural infestation of weeds first reduced dry bean yield, and when weed removal could be discontinued without further loss of seed yield. Major weeds in order of average biomass production on weedy check plots at dry bean harvest over locations and years were wild mustard, foxtail spp., redroot pigweed, common ragweed, wild buckwheat, hairy nightshade, and common lambsquarters. Hairy nightshade also emerged late in the growing season and could negatively affect harvest efficiency and stain navy beans. Weed removal treatments had little effect on dry bean stands or 100-seed weights of harvested dry bean seed. The critical period for weed control in dry beans was 3 to 5 or 6 weeks after planting (WAP). Thus, weed control practices should begin no later than 3 WAP and continue until at least 5 or 6 WAP for maximum dry bean yields.

Cultural practices, such as delayed crop seeding, tillage, black fallow, crop rotation, hand weeding, and competitive crops, when used to replace herbicides, provide an opportunity to reduce the selection pressure that causes weeds to become resistant to herbicides. Herbicides on the other hand reduce the selection pressure that causes weeds to resist cultural practices. Rotation of the two systems should then delay resistance to both systems. Growers consider many factors in addition to weed resistance in selecting herbicide or cultural weed control, from associated convenience to economic potential. Rotation of different types of weed control practices would delay resistance, compared to a continuous single practice. The extent of the delay depends upon genetics of resistance, weed reproduction characteristics, weed seed survival, and fitness of resistant weed plants. An understanding of the basic aspects of weeds and herbicides, as well as their interaction with the environment, would help in predicting the delay in resistance to an herbicide from use of cultural practices in the rotation. A grower's final choice of a weed control practice will involve available equipment, time, markets, and soil erosion in addition to potential weed resistance. Weeds that develop resistance to a control practice still allow for reversion to preresistance practices, an important component of a grower's decision. The rate of resistance development is dependent upon the removal of susceptible genes from the population and fitness of the resistant plants. Resistance might be delayed for many years or be manageable when the resistance is genetically recessive or resistant weeds are poorly fit. Growers may not want to accept alternative cultural practices as long as there is the potential for development of another herbicide or reversion to cultural control after resistance occurs.

Various combinations of methods were evaluated for the control of ivyleaf morningglory growing in cotton. The combinations included chemicals incorporated to two depths or tanked-mixed as postemergence treatments and cultural methods that included in-row cultivation and hand weeding. The most effective combinations of methods included a herbicide such as cyanazine or prometryn in some treatments resulting in reduced ivyleaf morningglory population and improved cotton yields. Cultural methods without chemical assistance gave little or no control of ivyleaf morningglory based on weed populations and cotton yield. Statistically the best combinations had lint yields equal to the weed-free treatment, but the yields were reduced from 114 to 372 kg/ha. Also, most combination treatments had enough plant debris in the lint to reduce fiber grade.

A field experiment was conducted near Davis, CA, during the 2003 and 2004 summer growing seasons to compare weed control, yield, and fruit quality in different irrigation and tillage systems in processing tomato. Trial design was a subplots with the main plots as subsurface drip irrigation or furrow irrigation, subplots were standard tillage or conservation tillage, and sub-subplots were herbicide or no herbicide. The hypothesis was that subsurface drip irrigation could limit surface soil wetting and thus inhibit germination and growth of weeds equal to or better than standard tillage and/or herbicides. In both 2003 and 2004, weed densities in the subsurface drip irrigation treatments were over 98% lower than the levels in furrow irrigation treatments. In addition, weed densities were lower in the subsurface drip–conservation till–no herbicide treatment than in any of the furrow irrigation treatments, including the furrow irrigation–standard tillage–herbicide treatments. The time required for a hand-hoeing crew to remove weeds was 5 to 13 times greater in furrow irrigation treatments compared to subsurface drip irrigation treatments. Weed biomass on beds at tomato harvest was 10 to 14 times greater in the furrow systems as compared to the subsurface drip irrigation systems. These results demonstrate the effectiveness of subsurface drip irrigation in controlling weed germination and growth, compared to tillage or herbicide applications. Tomato yield was higher in the subsurface drip irrigation treatment compared to furrow irrigation in 2004. Herbicide treatment increased yield in 2004, but only in the furrow irrigation treatment in 2003. Fruit brix level was not related to treatment in 2003, but was lower in the subsurface drip irrigation plots in 2004. These results indicate that subsurface drip irrigation can reduce weed competition in conservation tillage systems, without requiring herbicide applications.

Time requirements, weed control efficacy, and yield effects of three labor-saving weed technologies were tested against hand weeding during three seasons in 2012 and 2013. The technologies included two hand-operated mechanical weeders, the straight-spike and the twisted-spike floating weeder, and the PRE application of oxadiazon. The straight-spike floating weeder reduced weeding time by 32 to 49%, the twisted-spike floating weeder reduced weeding time by 32 to 56%, and the application of herbicide required 88 to 97% less time than hand weeding. Herbicide application provided the best weed control in two of the three seasons. No differences in weed control efficacy were observed between mechanical and hand weeding. Yield differences were only observed in season 3 with higher rice yields after PRE application of oxadiazon compared with other weed management treatments.

Edamame, a specialty food-grade soybean popular among health-conscious consumers, is growing in popularity worldwide. Despite a well-developed soybean industry, most edamame consumed in the United States is imported from Asia. Considerable interest exists in growing edamame domestically; however, weed interference is a major problem, and until recently, only a single herbicide was registered for use on the crop. The objectives of this work were (1) to compare effectiveness of weed management treatments that utilize herbicides currently registered for use on edamame or that may be registered in the near future, (2) to determine the significance of edamame cultivar on performance of these treatments, and (3) to identify potential relationships between the crop and weed. Ten different weed management treatments were tested in three edamame cultivars over a 3-yr period. All weed management treatments increased marketable pod yield relative to the nontreated control, but only treatments with saflufenacil or S-metolachlor combinations were comparable to the hand-weeded weed-free treatment. Of the treatments studied, S-metolachlor followed by imazamox was among the greatest yielding, had the least weed density and biomass, and did not reduce crop population density. Also, cultivars differed in their weed-suppressive ability. Path analysis indicated certain relationships were consistent across cultivars, such as weed population density having a direct negative association with crop biomass; however, other edamame–weed interactions were not identical across cultivars. Although more improvements are needed, the vegetable industry is beginning to have nascent weed management options in edamame, which will likely reduce reliance on hand weeding and result in crop-production costs that are more competitive in the global market.

Most studies on weed population dynamics in farming systems have focused on the effects of different weed control strategies. Those studies usually assume that farmers, operating within a particular system, have a uniform management style. However, it is likely that weed management decision making also varies between farmers that operate within a system. In this study, the relationship between weed management behavior and the outcome of that behavior within an organic farming system is studied. It is hypothesized that differences in weed pressure between organic farms can be related to differences in farmers' weed management behavior. We explore which weed and general management factors are of main influence on the weed pressure, and investigate the influence of farmer's beliefs and knowledge on weed control techniques and the observed weed pressure. Preventive measures and timing of main soil tillage operation were identified as the weed management factors most influential for weed pressure. With the increasing number of preventive measures applied, weed pressure decreased, with a stale seedbed being the most important preventive measure. The weed pressure increased with the number of days after September 1st on which the main tillage operation was carried out. Because of this postponement of the tillage treatments, the growing season of weeds was extended and more species were able to reproduce before winter, thereby enhancing weed pressure. Field size, rather than weed pressure, determined the number of hand-weeding hours per ha; with increasing field size the amount of hand weeding per surface area was reduced. On farms with lower weed pressures a higher percentage of competitive crops were grown than on farms with higher weed pressures. The farmer's beliefs and knowledge on weed control techniques differed between farmers with different weed pressures. Market-oriented growers had a higher on-farm weed pressure than crop-growth–oriented growers. It was concluded that studies on weed management behavior and the effect of that behavior can lead to a better understanding of farming systems and to more effective weed management in those systems.

Chemical, mechanical, and biological methods are used to manage invasive plants, but their effectiveness at removing specific plant invaders while preserving native communities varies widely. Chemical methods are used most extensively but the nontarget effects of some herbicides can have lasting effects on native plants. Nonchemical methods are needed for sites containing rare or threatened native species and where the cost of herbicides is prohibitive. Here we evaluate multiple nonchemical methods for removing Japanese stiltgrass, a nonnative annual grass that is rapidly invading eastern U.S. forests. We applied mowing, hand weeding, and spring and fall fire treatments to replicated plots at three forested sites in southern Indiana and compared the response of Japanese stiltgrass and native plants to untreated reference plots. Mowing and fall fires applied just before seed set were the most effective methods for removing Japanese stiltgrass. Mowing decreased invader cover by 70% and biomass by 95%, whereas fall fires reduced cover by 79% and biomass by 90% compared to reference plots. Spring fire reduced Japanese stiltgrass cover, but not biomass, and hand weeding did not significantly reduce invader cover or biomass compared to untreated plots. There were no significant differences in the response of the overall native plant community or of specific native plant functional groups to the removal treatments. In summary, mowing and properly timed fall fires may be effective nonchemical methods for managing Japanese stiltgrass invasions and restoring native communities. Future research should focus on evaluating the responses of Japanese stiltgrass, native species, and other plant invaders to removal treatments conducted over successive growing seasons across a range of invaded habitats.

Lentil is vulnerable to weed competition because of its short stature, slow establishment, and limited vegetative growth. Although the vast majority of lentil production is under rain-fed conditions, there is a little published information on weed control with herbicides in rain-fed lentils. Field experiments were conducted to determine the efficacy of nine herbicide treatments including fomesafen, imazethapyr, linuron, pendimethalin, and pyridate alone or in combination compared with one or two hand weeding(s) on weed control and yield response in rain-fed lentil in Khorramabad, Iran in 2012 and 2013. Weed species included catchweed bedstraw, cowcockle, haresear mustard, hoary cress, wild mustard, and wild safflower. Total weed dry biomass in weedy check plots averaged 156 and 170 g m−2 in 2012 and 2013, respectively, and weed density and biomass were reduced in all treatments compared to the weedy check in both years. Plots that were hand weeded twice reduced weed biomass the greatest, whereas fomesafen, linuron, or one hand weeding did not control weeds satisfactorily. Noncontrolled weeds reduced lentil yield by 67% both years compared to the weed-free control. Lentil yield in 2013 (1,370 kg ha−1) was higher than in 2012 (1,150 kg ha−1). All herbicides tested injured lentil slightly, with pyridate (1,200 g ai ha−1) and pendimethalin (660 g ai ha−1 plus imazethapyr at 250 to 500 g ai ha−1) causing the least injury. Across all treatments, imazethapyr plus pendimethalin PRE, pyridate POST, and two hand-weeding treatments had the best performance for weed control and lentil yield.

Winter sowing of lentil results in higher yields than a spring-sown crop. However, when lentil is winter-sown, the critical period of weed control is extended and might require sequential herbicide management strategies to obtain maximum yields. The efficacy of POST alone or soil applied followed by (fb) POST herbicides or hand weeding were evaluated in 2002 and 2003. Trifluralin (PPI) or pendimethalin (PRE) were applied at planting, and pyridate or oxyfluorfen were applied POST at the three- to four-leaf stage of lentil. The lowest level of weed biomass was recorded with all treatments, except pyridate alone in both years, pendimethalin PRE fb pyridate in 2002, and oxyfluorfen in 2003. Application of pyridate or oxyfluorfen POST alone resulted in lower yields. In 2002, trifluralin PPI or pendimethalin PRE fb one hand weeding or pendimethalin fb pyridate resulted in yields similar to the weed-free treatment. In 2003, yields were similar to the weed-free treatment, except pyridate or oxyfluorfen alone and trifluralin PPI fb oxyfluorfen. Weed species observed in the present study required sequential management to achieve both effective control and maximum lentil yield.

Weed management is a major constraint in organic production. It can be expensive and time-consuming and severe crop yield losses may be incurred when weeds are not adequately controlled. Research on organic weed management (OWM) in herb and vegetable production is increasing internationally, although in Australia very little work has been done to assess current OWM knowledge among growers, and to test the efficacy and cost effectiveness of the weed management practices used by organic growers. The effect of hand weeding, tillage, hay mulch, pelletized paper mulch (PP) and an unweeded control treatment on weed growth, crop growth and cost effectiveness were evaluated in several field trials on the Northern Tablelands of New South Wales using lettuce (Lactuca sativa L.) and echinacea (Echinacea purpurea Moench. [L.]). In echinacea, hand weeding, hay mulch and PP reduced weed growth by at least 90% compared with the control, while tillage reduced weed levels by about 50%. The more expensive weeding methods such as hand weeding and hay mulch (AU$9600 and 8900 ha−1 respectively) produced higher yields, while the cheaper methods such as tillage ($4000 ha−1) had low crop yields and were therefore 25–50% less cost effective. In lettuce, weed growth was reduced by 96% for hand weeding and PP compared with the control, 85% for hay mulch and 66% for tillage. Weed management was cost-effectively achieved using cheaper weeding methods such as tillage ($985 ha−1) compared with more expensive methods such as hand weeding and hay mulching ($4400 and 7600 ha−1 respectively). PP had lower yields and was expensive ($12,500 ha−1) and was usually not cost effective in these trials. The results highlight several important advantages and disadvantages of currently used OWM methods in the field.

Weed management is often the most troublesome technical problem to be solved in organic farming, especially in poorly competitive crops like vegetables. A four-year (2000–2003) series of trials was established to assess the possibility of adopting an innovative non-chemical weed management system in organic carrot grown on the Fucino plateau, i.e., the most important carrot-growing area in Italy. The system utilized for physical weed control was based first on a false seedbed technique followed by pre-sowing weed removal, performed with a special 2 m wide 6-row spring-tine harrow. Prior to crop emergence, a pass with a flame weeder equipped with four 50 cm wide-open flame burners was also performed. Post-emergence weed control consisted of one or more hoeing passes with a purpose-designed 11-tine precision hoe equipped with spring implements (torsion weeders and vibrating tines), in addition to hand weeding. This innovative system was applied to a novel planting pattern (sowing in ten individual rows within 2 m wide beds) and compared to the standard management system of the area (sowing within 2 m wide beds but in five bands, use of spring-tine harrowing and flame weeding pre-emergence and of traditional hoeing post-emergence). The new system was tested in different commercial farms including both early and late-sown carrot. Assessments included machine operative characteristics, labor time, weed density and biomass, crop root yield and yield quality, and economic data (physical weed control costs and crop gross margin). Compared to the standard system, the innovative system usually resulted in reduced labor time (from 28 to 40%) and total costs for physical weed control (on average −416 € ha−1). Use of the precision hoe resulted in intra-row weed reduction ranging from 65 to 90%, which also led to a marked reduction in the labor required for hand weeding. In 2001 the two systems did not differ in terms of yield and yield quality, whereas in 2002 and 2003 the innovative system showed a higher mean density of carrot plants (from 28 to 55%), root yield (from 30 to 42%), and gross margin (from 40 to 100%). Carrot yield was higher in farms which adopted an early sowing whereas root commercial quality was somewhat variable between systems and years. In general, results obtained with the innovative management system look very promising.