Weed control and yield response to mesotrione in maize (Zea mays)

Mesotrione has recently been registered for weed control in maize in Ontario, Canada; however, there is still little information on the doses required to provide 90% control for the complete spectrum of broadleaved weeds that the product controls. Our objective was to determine mesotrione doses that would provide at least 90% control of four economically important weeds, without impacting final maize yield by more than 5% in comparison to a weed-free control. Sixteen field trials were conducted at six Ontario locations in 1999–2001 to evaluate the effectiveness of mesotrione at doses ranging from 9 to 280 g ai ha⁻¹. The doses required to reduce weed biomass by at least 90% (I₉₀) varied with location and year, and for common lambsquarters and velvetleaf differed by application timing. For lambsquarters, the estimated doses required ranged from 10 to 1984 g ai ha⁻¹ for preemergence applications and 15–38 g ai ha⁻¹ for postemergence applications. Doses of 45 and 19–243 g ai ha⁻¹ were required to effectively reduce the biomass of redroot pigweed. Velvetleaf was effectively controlled preemergence with 288 g ai ha⁻¹ and postemergence with 31 g ai ha⁻¹ of mesotrione. Final maize yield was only reduced by more than 5% of a weed-free control when a dose of less than 35 g ai ha⁻¹ of mesotrione was applied. These results show that biologically effective weed control with reduced doses of mesotrione is possible depending on the spectrum of broadleaved weed species present in the field.     

Weed control with selected herbicides in acetolactate synthase-resistant sorghum

The recent development of grain sorghum hybrids with resistance to acetolactate synthase (ALS)-inhibiting herbicides has allowed for the use of several post-emergence applied (POST) ALS-inhibitors to control weeds in the crop. Field experiments were conducted at four sites in Kansas in 2008 to evaluate the efficacy of nicosulfuron and nicosulfuron + rimsulfuron applied alone or in combination with dicamba, metsulfuron methyl, and atrazine. All POST treatments slightly injured sorghum 2 weeks after treatment (WAT) at Garden City and Hesston, whereas at Hays and Manhattan, only treatments that included dicamba caused injury. Nicosulfuron + rimsulfuron applied alone provided 41, 83, 74, and 93% control of grasses 4 WAT at Garden City, Hays, Hesston, and Manhattan, respectively. However, to obtain the highest level broadleaf weed control, nicosulfuron or nicosulfuron + rimsulfuron need to be applied with other broadleaf herbicides. POST treatment of nicosulfuron + metsulfuron methyl + dicamba + atrazine provided 90% or greater control of all broadleaf weeds at sorghum flowering. Sorghum grain yield was greater following all herbicide treatments compared with the weedy check. The POST treatment that provided the highest yield at Garden City was nicosulfuron + rimsulfuron + atrazine, whereas in Hesston and Manhattan, nicosulfuron + metsulfuron methyl + dicamba + atrazine provided the highest yields. This research showed that many grasses can be effectively controlled with POST applications of nicosulfuron or nicosulfuron + rimsulfuron in ALS-resistant sorghum. The research also indicated that broadleaf weed control is greater when nicosulfuron or nicosulfuron + rimsulfuron are applied with other broadleaf-control herbicides such as dicamba, metsulfuron methyl, and atrazine.     

Effect of herbicides on weed management in dry-seeded rice sown under different tillage systems

In India, dry-seeded rice (DSR) production systems are rapidly replacing conventional rice production systems due to various advantages. DSR systems can be managed under zero-till (ZT) conditions or after a preparatory tillage, often referred to as conventional tillage systems (CONT). Although previous reports indicate the contribution of tillage to weed suppression, the effect of one-time preparatory tillage in a DSR system could vary depending on the dominant weeds in the system, vertical seed distribution and the weed seed dynamics. A study was conducted to test the efficacy of ZT and CONT and their interaction with herbicide treatments on the weed population dynamics and rice grain yield in 2010 and 2011. Tillage systems did not affect weed emergence, weed biomass, tiller production and crop yield. However, herbicide treatments varied in their efficacy on individual weeds. Hand-weeding treatments and pendimethalin combined with hand weeding did not effectively control Cyperus rotundus L. and Panicum maximum Jacq. (a perennial grass weed with underground parts). The herbicide combination of metsulfuron and chlorimuron was effective in controlling C. rotundus but not grass weeds. This indicates the need for sequential applications of herbicides for grass weed control or integration of hand weeding to achieve broad-spectrum weed control. Apart from hand weeding (three times), treatment with penoxsulam–cyhalofop and pendimethalin followed by (fb) hand weeding resulted in low weed density, high tiller production and grain yield. The study clearly indicates that tillage does not always lead to weed suppression compared with ZT, and herbicides must be chosen based on the dominant weeds in a system. The results of this study are pertinent as herbicide-resistant weeds are rapidly evolving under continuous herbicide selection pressure, which warrants studies on enhancing productivity through low-input, environmentally friendly and sustainable production technology.     

玉米田常用除草剂对苘麻室内除草活性研究

采用盆栽法研究异噁唑草酮、莠去津、硝磺草酮、苯唑草酮等常用除草剂单用及混剂对苘麻的除草活性及对玉米的安全性。结果表明，异噁唑草酮 75.98 g/hm²+莠去津 900.00 g/hm²混用进行土壤封闭处理对苘麻的抑制率最高，药后 14 d的鲜重抑制率为 91.61%，显著高于两种药剂单一使用的除草活性；苯唑草酮 20.20 g/hm²+莠去津 900.00 g/hm²混用进行茎叶处理对苘麻的抑制率最高，药后 14 d的鲜重抑制率为 91.20%，显著高于两种药剂单一使用的除草活性，所有处理对玉米生长无影响。除草剂混用对苘麻的除草活性均高于单一除草剂，且达到除草剂使用减量增效的作用。因此，玉米 3～4叶期喷施异噁唑草酮 75.98 g/hm²+莠去津 900.00 g/hm²或苯唑草酮 20.20 g/hm²+莠去津 900.00 g/hm²组合在生产上能有效防除苘麻。     

Weed control and sweet maize (Zea mays L.) yield as affected by pyroxasulfone dose

Pyroxasulfone is a new herbicide being considered for registration in sweet maize in Canada; however, there is still little information on the doses required to provide 90% control of annual grass and broadleaved weeds found in southwestern Ontario. The objective of this study was to determine pyroxasulfone doses that would provide at least 90% control of several economically important weeds, without impacting final sweet maize yield by more than 5% in comparison to a weed-free control. Six field trials were conducted over a two-year period (2007 and 2008) at three Ontario locations to evaluate the effectiveness of pyroxasulfone at doses ranging from 31.25 to 1000 g a.i. ha⁻¹. The doses required to reduce weed biomass by at least 90% (I₉₀) varied by weed species. Doses of 93, 499, and 111 g a.i. ha⁻¹ were required to reduce the biomass by 90% of redroot pigweed, common lambsquarters and green foxtail, respectively. There was greater than 95% control of velvetleaf, large crabgrass and barnyardgrass with 31.25 g a.i. ha⁻¹, the lowest dose tested. Sweet maize yield could not be consistently maintained within 5% of the weed-free control. There are several factors that may have contributed to the reduced yield, including soil texture effects, competition as a result of poor common lambsquarters control, and hybrid sensitivity. These results show that biologically effective weed control with pyroxasulfone may be achieved at lower than proposed doses for several weed species; it remains unclear if this is economically sustainable due to the potential impacts on yield.     

Integration of soil-applied herbicides at the reduced rates with physical control for weed management in fennel (Foeniculum vulgare Mill.)

Fennel has been widely used in traditional medicine for their antimicrobial effects. Since fennel is long duration crop and have slow initial growth, it protection from weed is essential. Experiments were conducted for two consecutive seasons to evaluate the efficacy of soil-applied herbicides at the reduced rates in combination with physical control for weed management and optimizing the yield of fennel. Treatments were type of herbicide (trifluralin and pendimethalin), application dose (recommend dose (R), 75% R, 50% R, and 0% R) and physical weed control (none, one hand-weeding at 50 day after planting (DAP), wheat straw mulch). Weed-free control treatment was also included in each year. The results showed that the use of soil-applied herbicides resulted in reduced weed biomass but did not provide season long weed control without an additional physical control. In both seasons, pendimethalin provided better weeds control than trifluralin. Reduced herbicide rates were found to be more effective when herbicides application followed by hand-weeding than when were used alone or combined with mulch. Experimental results also showed that one time increasing in herbicide rates increased seed yield by 17.5 and 7.5% in 2012 and 16.5 and 6.3% in 2013, when one hand-weeding and mulching were used as supplemental control, respectively. Overall, the 75% of the labeled recommended rate of herbicides followed by one hand-weeding at 50 DAP produced consistently high yields and less weed biomass, reflecting both superior weed control and crop safety.     

Effects of mechanical and chemical methods on weed control,weed seed rain and crop yield in maize,sunflower and soyabean

Eight field experiments with maize (Zea mays L.), sunflower (Helianthus annuus L.) and soyabean (Glycine max (L.) Merr.) were carried out in central Italy in order to evaluate the effects of mechanical and chemical methods (spring-tine harrowing, hoeing, hoeing-ridging, split-hoeing, finger-weeding, herbicides in the row + inter-row hoeing, herbicides broadcast) on weed control, weed seed rain and crop yield. The choice of chemical and mechanical treatments in maize and soyabean compared to sunflower, required to be managed more carefully in order to maximize the weed control reducing yield losses. A global rating of weed control methods, based on their weed control efficacy, was obtained as useful means to assist farmers and technicians to choose the more appropriate weed control method. The combination of herbicides intra-row and hoeing inter-row gave best efficacy (on average 99% of weed control), with a 50% reduction in the chemical load in the environment. Hoeing-ridging gave good results, both inter- and intra-row (on average 93% of weed control); this method was also effective in reducing competitive ability and seed production of uncontrolled weeds. Split-hoeing or finger-weeding showed some limitations giving satisfactory results only when combined. Harrowing gave lowest weed control, although when combined to other mechanical methods, can help achieve a better efficacy.     

Response of maize (Zea mays L.) to post-emergence applications of topramezone

Topramezone is a new herbicide for post-emergence control of broadleaf and grass weeds in maize. Two field experiments were conducted in northern Greece in 2008 and 2009 to determine the response of grain maize to topramezone applied with the adjuvant DASH at 2–4, 4–6 and 6–8 maize leaf stage. In both years, plant height, cob number and yield were not differently affected with the use of herbicide at these growth stages, indicating no difference in selectivity and a similar response of maize to the three post-emergence applications of topramezone. Slight injury symptoms of leaf bleaching were observed in the second year, however, they were transient with no lasting injury on maize growth.     

4种除草剂对夏玉米田杂草及麦苗的防效与安全性比较

选用4种莠去津复配剂进行玉米田杂草防除效果及安全性研究,筛选对夏玉米田杂草及自生麦苗的防效及安全性较好的除草剂。结果表明,31.5%噻酮磺隆·异噁唑草酮+38%莠去津总杂草株防效为88.7%,鲜质量防效为98.48%,防效较好,无明显药害症状,且玉米产量为各药剂处理中最高;22%烟嘧·莠去津和30%苯唑草酮+助剂+38%莠去津对自生麦苗株防效均在80%以上,鲜质量防效在95%以上;30%苯唑草酮+助剂+38%莠去津对莎草的株防效仅45.58%,莎草为主的夏玉米田块尽量不使用。     

喷雾助剂在烟嘧磺隆减量化防治玉米田杂草中的应用研究

以表面张力、扩展直径、干燥时间和最大持液量为评价指标,测定植株油类喷雾助剂GY-Tmax、矿物油类助剂GY-T12及有机硅类助剂GY-S903喷雾助剂不同添加量对40 g/L烟嘧磺隆可分散油悬浮剂药液物理性状的影响。结果表明,3种助剂均能显著降低其药液的表面张力,增加其扩展直径,GY-S903对其影响最大。3种助剂对药液的干燥时间和最大持液量的影响存在显著差异。添加0.25%～0.75%的GY-Tmax,在保证对玉米田杂草防治效果相当的情况下,烟嘧磺隆用量可减少50%;添加0.03%～0.07%的GY-S903及0.3%～0.6%的GY-T12可使烟嘧磺隆用量减少40%。在整个生育期内,未发现40 g/L烟嘧磺隆可分散油悬浮剂30 g ai/hm~2添加喷雾助剂各处理对玉米的明显受害症状,烟嘧磺隆添加GY-Tmax较30 g ai/hm~2烟嘧磺隆增产6.6%～7.6%,增产作用最强。GY-S903对烟嘧磺隆的增产作用与GY-T12相当,较30 g ai/hm~2烟嘧磺隆处理分别增产4.3%～7.0%及3.9%～7.4%。     

不同类型助剂对除草剂硝磺草酮的增效作用研究

通过生物试验结合仪器分析的方法，研究不同类型助剂对除草剂硝磺草酮的增效及相关机制和对玉米的安全性。结果表明，5种助剂均能改变药液物理性状，提高硝磺草酮对玉米田杂草的防效。添加助剂后硝磺草酮药液稳定性增加、药液液滴表面张力和接触角降低、药液黏度提高是其杂草防除效率提升的主要物理机制。液相色谱分析证明，助剂对硝磺草酮在苘麻叶片上的吸收增量排序为新型复合类油剂>新型复合类水剂>有机硅类助剂>非离子表面活性剂>油类助剂。5种供试助剂中，新型复合类油剂、水剂对药液性状影响最显著，与对照相比，显著增加在苘麻叶片上的吸收量129.74%～176.59%、112.87%～147.63%；对玉米田间杂草增效作用最明显，提高21.05%～22.24%；对玉米各阶段生长发育有显著促进作用，最终提高产量15.85%～17.38%。     

Weed control in conservation agriculture systems of Zimbabwe: Identifying economical best strategies

Weed management under conservation agriculture (CA), especially when manually controlled is one of the major setbacks for the widespread adoption of CA in southern Africa. This study was conducted at three on-station and three on-farm sites: CIMMYT-Harare, Domboshawa Training Centre and Henderson Research Station (on-station sites), Hereford farm, Madziva communal area and Shamva communal area (on-farm sites). The evaluation focused on the effect of initial herbicide application and succeeding manual weeding whenever weeds were 10 cm tall or 10 cm in length for grasses with stoloniferous–rhizomatous growth habit. Weeds counts, weeding time and grain yields were collected at all on-station sites. At the on-farm sites, weed counts were done before weeding and a number of farmers were timed during weeding. The results showed that herbicides use reduced the weed density and time taken on weeding at all sites. Combining herbicides e.g. atrazine, glyphosate and metalachlor had the lowest weed density and weeding time at all sites. However, the treatments had no effect on maize grain yields suggesting that appropriate and timely manual weeding reduced crop/weed competition. Herbicides treatments had higher input costs than manual weeding due to the additional cost of herbicide but the treatment with manual weeding only had more overall labour days compared to the mixture of three herbicides. In order to achieve economic benefits, smallholder farmers may use the time for value addition e.g. expand cropped land area, use time for value addition, or sell new products on the market. Herbicides use reduces the manual labour needed to control weeds and minimise total crop failure due to untimely weeding hence, herbicides are an important but not the only weed control option under CA systems in Zimbabwe.     

Chemical control of weeds in transplanted tomatoes in Saudi Arabia

The herbicides metobromuron, diphenamid and dinitramine were tested either singly or in combination with dalapon for the control of weed species in transplanted tomato crops in Saudi Arabia, during 1979 and 1980. All herbicides were effective in controlling Chenopodium murale L., the primary broad-leaved weed in the area. However, they were less effective against other broad-leaved weed species and, even in combination with dalapon, failed to reduce populations of grass weeds. Tomato seedlings showed various degrees of injury: dinitramine was the most phytotoxic herbicide, followed by metobromuron and diphenamid. No toxicity was observed for dalapon. Diphenamid was the most promising herbicide for controlling weeds and producing significantly higher yields of tomatoes.     

Weed control and wheat (Triticum aestivum L.) yield under application of 2,4-D plus carfentrazone-ethyl and florasulam plus flumetsulam: Evaluation of the efficacy

Three field experiments were conducted at the research fields of Plant Protection Research Institute, Iran, at different locations in 2004–2005 to study the efficacy of different broadleaved herbicides to control weeds in wheat. Treatments were the full-season hand weeded and weed-infested controls, and post-emergence applications of florasulam plus flumetsulam at 8.75, 10.50, and 12.25 g a.i./ha, 2,4-D plus carfentrazone-ethyl at 210, 245, 280, and 490 g a.i./ha, bromoxynil plus MCPA at 75, 100, and 150 g a.i./ha, 2,4-D at 560, 720, and 1120 g a.i./ha, tribenuron methyl, and 2,4-D plus MCPA. Herbicides were applied at wheat tillering stage. Naturally occurring broadleaved weed populations were used in experiments. Results indicated that bromoxynil plus MCPA at 150 g a.i./ha, 2,4-D plus MCPA, and 2,4-D plus carfentrazone-ethyl at 490 g a.i./ha were the best options to control weeds. Bromoxynil plus MCPA at 150 g a.i./ha and 2,4-D plus MCPA also resulted in the highest wheat yield. Overall, it could be concluded that rotational application of bromoxynil plus MCPA at 150 g a.i./ha, 2,4-D plus MCPA, and 2,4-D plus carfentrazone-ethyl at 490 g a.i./ha would be the best option to achieve satisfactory weed control, high grain yield and prevention of evolution of herbicide-resistant weeds.     

Weed management in maize using crop competition: A review

Weeds are a major constraint to crop production, and are responsible for considerable yield losses in maize production systems throughout the world. Herbicides are widely used for weed control in maize production systems, but can have negative environmental consequences. Researchers have evaluated the use of crop competition and suppression to manage weeds in various crop combinations, including maize-based systems. Crop competition in maize may involve techniques such as reduced row spacing, increased planting density, and the use of competitive cultivars that exhibit weed suppressive potential. In this review, examination of the literature has revealed the considerable value of using crop competition in integrated weed management programs. Research has demonstrated that narrowing row spacing to half the standard distance reduced weed biomass by 39–68%, depending on weed species. Researchers have also demonstrated that increasing maize planting density by up to twice the standard rate achieved a reduction in weed biomass of 26–99%. While little research has been conducted into the use of competitive maize cultivars for weed management, several studies have documented cultivars with potential to suppress weeds. Attributes of weed competitive cultivars include high leaf area index, and other elements of leaf architecture that improve light interception by the crop, so increasing the shading of weeds. Combining crop competition methods with other agronomic practices can increase their effectiveness in controlling weeds. For example, biomass of Setaria italica (L.) Beauv was reduced by 60% when maize planting density was increased by 1.5 times the recommended spacing, and this effect was more pronounced when fertilizer was banded rather than broadcast. In summary, the strategic use of crop competition to control weeds has been a success in many regions, and is an important tool in integrated weed management. The importance of crop competition methods has particular relevance where farmers are unable to afford herbicides, as making use of crop competition is more economical.     

不同氮肥施用量对东北玉米田杂草发生的影响

利用吉林省梨树县黑土区氮肥长期定位试验田(施氮水平为0、60、120、180、240、300 kg/hm~2),2019～2020两年调查玉米田杂草种类、密度和生物量及其与玉米生物量和产量的关系。结果表明,试验条件下玉米田杂草主要是禾本科杂草,尤其是水稗草Echinochloa oryzoides。与不施肥相比,60 kg/hm~2施氮量增加杂草密度和生物量;随氮肥施用量的增加,杂草的密度和生物量均显著降低。在180 kg/hm~2供氮量时,杂草的密度和生物量达到最低,分别比60 kg/hm~2施氮量的最大值下降81%～94%和90%,玉米产量达到最大。与180 kg/hm~2施氮量相比,进一步增加施氮量,玉米产量不增加,杂草的密度和生物量也不再减少。因此,从施肥经济效益和杂草防控两个方面结合考虑,该地区最优施肥量为180 kg/hm~2。     

硝磺草酮与二氯吡啶酸复配应用于玉米田除草效果测定

采用室内生物测定方法,研究硝磺草酮与二氯吡啶酸复配联合作用类型,对复配制剂进行田间效果试验。结果表明,硝磺草酮对马唐、稗草效果较好,对马齿苋、铁苋菜效果差;二氯吡啶酸对马齿苋、铁苋菜效果较好,对马唐、稗草近无效。两者复配后优势互补,作用类型均为相加作用。硝磺草酮与二氯吡啶酸两者混配剂可作为备选药剂进行田间试验,茎叶处理防除玉米田杂草,推荐比例为0.67~2.67∶1。田间试验结果表明,硝磺草酮与二氯吡啶酸复配后综合两种单剂优势,对试验田杂草马唐、马齿苋、铁苋菜和苘麻均有很好效果。     

Management of complex weed flora in dry-seeded rice

Dry-seeded rice has been introduced as an alternative to puddled hand-transplanted rice in the north Indian states of Punjab and Haryana. In dry-seeded rice, weed flora tends to be more diverse and weeds emerge in several flushes during the crop growth cycle and substantial yield reductions due to weed competition are quite common. The efficacy and compatibility of tank mixtures of different herbicides for the control of diverse weed flora in dry-seeded rice was evaluated in field experiments during the summer seasons of 2012 and 2013. The tank mixture of fenoxaprop with ethoxysulfuron improved the control of Echinochloa crus-galli and Echinochloa colona by 43–69% as compared to fenoxaprop alone while the tank-mix of azimsulfuron with fenoxaprop was antagonistic and reduced the control of Leptochloa chinensis by 86% as compared to fenoxaprop alone. Addition of azimsulfuron or ethoxysulfuron to bispyribac did not improve the control of grass weeds as compared to bispyribac alone. Weed control with the mixture of bispyribac and fenoxaprop varied over the two years. In 2012, bispyribac and fenoxaprop mixture was antagonistic for the control of Dactyloctenum aegyptium, Acrachne racemose, and L. chinensis but in 2013, there was no apparent antagonism and the addition of bispyribac to fenoxaprop reduced grass weed biomass as compared to fenoxaprop alone. In 2013, there was a strong negative correlation (r = −0.95, P < 0.001) between weed dry matter at 45 days after sowing and rice grain yield. According to the linear regression, rice crop is likely to produce no grain yield when weed dry matter exceeds 400 g m⁻². Over the two seasons, fenoxaprop-ethoxysulfuron tank-mix produced similar grain yields (5.6–6.2 t ha⁻¹) to the weed-free check (5.6–7.1 t ha⁻¹). At the farmer fields, rice grain yield in the plots treated with pendimethalin followed by post-emergence bispyribac or a tank-mix of fenoxaprop + ethoxysulfuron ranged from 6.2 to 7.7 t ha⁻¹ as compared to 5.3–5.6 t ha⁻¹ in the plots treated with pendimethalin alone. The tank mixture of fenoxaprop with bispyribac needs further evaluation as this mixture has the potential to effectively control aerobic and aquatic grasses in dry-seeded rice. Single hand weeding prevented crop yield loss from weeds that escaped herbicide treatments only when it was performed within six weeks of sowing.     

30%烟嘧磺隆·莠去津·硝磺草酮可分散油悬浮剂对甜玉米田杂草的防效及安全性

研究30%烟嘧磺隆·莠去津·硝磺草酮可分散油悬浮剂在甜玉米田的应用效果,在甜玉米不同叶龄期开展田间试验,评价其对杂草的防除效果及对甜玉米的安全性。结果表明,30%烟嘧磺隆·莠去津·硝磺草酮可分散油悬浮剂在甜玉米3～4叶期或6～7叶期施药,900～1 575 g a.i./hm2剂量范围内对甜玉米品种粤甜28安全,对玉米田常见杂草凹头苋、光头稗、马唐和香附子的防效及增产效果均显著高于对照药剂38%莠去津悬浮剂2 160 g a.i./hm2播后苗前处理。推荐30%烟嘧磺隆·莠去津·硝磺草酮可分散油悬浮剂在900～1 350 g a.i./hm2范围内,甜玉米3～5叶期茎叶喷雾使用。     

不同除草剂单独相继使用和混合使用防除小麦田虉草的效果比较

草是小麦田的主要杂草 ,尤其是水稻—小麦复种田块发生较为严重。用异丙隆防除　草已有 2 0多年的历史 ,防治效果十分显著。但近来有研究表明　草已具有对异丙隆的抗性。本试验研究了不同除草剂单独相继使用与混合使用对该杂草的防治效果。结果表明 ,播后 60 d,出苗前喷施氟乐灵和第一次灌水后喷施异丙隆的处理 ,除草效果最佳 ,而在成熟期 ,第一次灌水后喷施噻黄隆的处理具有与以上处理同样的防治效果。虽然使用异丙隆的处理产量最高 ,但一些除草剂单独相继使用也具有很好的杂草防治效果 ,小麦产量显著高于未用除草剂的对照。作者认为 ,在　草防治上存在有异丙隆抗性的地区 ,可以使用本研究中的一些除草剂