Expanding the Context of Weed Management

Abstract

Concerns about current weed control practices have increased the consideration of new weed management strategies. In recent times, weed control practices for major crops have been influenced greatly by the availability of selective herbicides. Herbicides are critical tools, but weed science must integrate more components to create weed management systems. Changes in weed management can be attained within the framework of existing cropping systems. However, for the longer term, new methods and approaches to weed management are needed. Weed scientists need to play a central role in the development of new cropping systems to make weed management an integral component of the system. This volume contains a series of review articles and original research that presents innovative approaches to weeds and weed management. It is our hope that these papers will stimulate discussion on a broader view of weeds and weed management.     

Weed hosts of the tobacco rattle virus in Idaho

The corky ringspot disease of potato (Solanum tuberosum) caused by the tobacco rattle virus (TRV) is a serious problem in certain Idaho localities. To investigate natural TRV sources, weeds and plants from rotation crops were randomly collected from six fields with a history of corky ringspot symptoms. Transmission trials, Ouchterlony agar double-diffusion tests, and electron-microscopy showed evidence of TRV in three Idaho counties (Fremont, Ada, and Canyon). Inoculations were made from 27 species and TRV was recovered from the roots of three:Solanum nigrum, Brassica campestris, andErodium cicutarium. Solanum nigrum was the most consistent source of TRV and it generally incited the severest symptoms onNicotiana tabacum (Samsun NN). The results show thatS. nigrum, besides being an important wild host of TRV, may be a useful naturallyoccurring bait plant for detection of TRV in field soils.     

Maximizing Efficacy and Economics of Mechanical Weed Control in Row Crops Through Forecasts of Weed Emergence

Abstract

In row crops of the North American Corn Belt two important forms of postplant mechanical weed control are rotary hoeing and inter-row cultivation. Unfortunately, the efficacies of these two control technologies are variable, which leads to high levels of economic risk. We hypothesized that efficacies and profitability of rotary hoeing and inter-row cultivation would increase, and risk would decrease, if the timing of control was based more on weed emergence times, than on rule-of-thumb calendar dates. Field research was conducted in soybean (Glycine max [L.] Merr.) for two years in Minnesota wherein four dates of rotary hoeing and three dates of inter-row cultivation, alone or supplemented by grass or broadleaf herbicides, were examined for weed control, crop yield, and net returns. Results indicate that timing influences the efficacy of mechanical control operations, but blanket optimal calendar windows that are generally applicable cannot be established, as such decisions may be location-specific and/or time-dependent. In contrast, efficacies appear more consistent if emergence percentages are used to decide the time of mechanical operations, e.g., rotary hoe at 30% and cultivate at 60% green foxtail (Setaria viridis [L.] Beauv.) emergence. The results also suggest that while it is possible for exclusive mechanical weed control to be optimal in some instances, consistently profitable weed control strategies will inevitably involve some herbicide usage.     

除草次数对杂草群落和夏玉米产量的影响

以山东省沂蒙山区夏玉米田为研究对象,设化学除草剂除草（CK）、不除草（W0）、苗期人工锄草1次（W1）、苗期+开花期人工锄草两次（W2）4种处理方式,研究除草次数对农田杂草生物多样性和对夏玉米产量的影响。结果表明,玉米田中9种杂草的多样性指数以W0处理最高,W1处理次之;花后40 d,W1、W2处理玉米地上部生物量与CK差异不显著（P>0.05）,W0处理与CK差异显著（P<0.05）;产量也表现出相同规律。研究表明,当地苗期适时进行1次除草,不仅能维持杂草多样性,而且可避免作物产量损失;与人工锄草两次相比,1次除草能省工省时,减少成本。     

糖料甘蔗生产杂草防除技术

主要从农业、化学、转基因等方面概述我国甘蔗杂草防除技术,并对甘蔗杂草防除技术研究中存在的问题及前景提出了展望。     

Weed control in rice seedling nurseries

Experiments were conducted in farmers' fields at Guimba, Nueva Ecija and at the International Rice Research Institute (IRRI), Los Baños, Laguna to test the efficacy of different methods of controlling weeds in rice (Oryza sativa L.) seedling nurseries. Hand weeding was laborious and ineffective due to the morphological similarities between rice and the Echinochloa species and the regeneration of perennial weeds. It was also injurious to rice seedlings. Manual separation of weed seedlings from rice seedlings before transplanting was ineffective, laborious, time consuming and expensive. Thiobencarb, butachlor, pretilachlor+fenclorim, propanil and quinclorac+bensulfuron were inexpensive and effective in controlling weeds in seedling nurseries without any deleterious effect on rice.     

水稻本田难治杂草防除药剂试验

通过不同除草药剂搭配使用,对稻田难治杂草进行防除试验,结果表明,施用瑞飞特各处理对禾本科杂草、阔叶杂草及非靶标杂草总体株防效与鲜重防效均为100%,施用阿罗津各处理均有不同程度的杂草发生,可见,50%瑞飞特与威农或吡嘧磺隆搭配二次灭草使用对杂草防效较好。     

影响黄河流域常规除草棉田机械采收的恶性杂草调查

为明确黄河流域棉区影响棉花机械采收的恶性杂草发生情况,于2013―2014年对河北、山东、天津共6个地点前、中期采取过不同除草措施的棉田杂草进行了调查。结果表明,播前使用过二甲戊灵的覆膜棉田,5月底行间(不包括膜下)有阔叶类杂草10科16种,占杂草总株数的96%左右;有禾本科杂草5种。2014年所有杂草的田间密度自5月底至6月底增长较快,之后部分阔叶类杂草和禾本科杂草缓慢增长,8月底以后保持稳定;另一部分阔叶类杂草6月底后即不再增长,至8月底或9月中旬后快速下降;7月底揭膜后杂草密度不再明显增加。前期和中期采取过除草措施的棉田,后期发生数量大、对机采影响也较大的普遍恶性杂草包括绕藤类的裂叶牵牛和亚灌木状的龙葵、苘麻、藜和反枝苋,区域性恶性杂草有攀援类的广布野豌豆和亚灌木状的苍耳。     

Weed management in aerobic rice systems

Aerobic rice systems can substitute the conventional rice cultivation system in the wake of water shortage and energy crises. The major constraint in the success of aerobic rice is high weed infestation. Hence, we have discussed the weed flora, yield losses, herbicide-resistant weeds, need for integrated weed management, and approaches to manage weeds in aerobic rice systems. A review of several studies indicated that 90 weed species were competing with rice under aerobic systems, causing 23–100% reductions in grain yield. Weed control in aerobic rice gets difficult due to shifts in weed flora and herbicide resistance development in weeds. A wide increase in grain yield (15–307%) by implementing different weed control practices elaborates the scope of weed management in aerobic rice. Practices, such as soil solarization, sowing of competitive crop cultivars, stale seedbed preparation, mulch application, correct fertilization, and intercropping, were found to have particular significance for managing weeds in aerobic rice systems. Moreover, hand weeding and mechanical control were more effective when combined with other weed control methods. Herbicides, such as pendimethalin, 2,4-D, penoxsulam, ethoxysulfuron, bispyribac-sodium, triclopyr, imazosulfuron, bensulfuron, pretilachlor, and metsulfuron, were found most effective in aerobic rice systems. Keeping in view the severity of weed infestation in these systems and the evolution of herbicide resistance, reliance on a single control method is out of question. Hence, the approach of integrated weed management is the most appropriate for proper weed management and the subsequent success of rice cultivation using aerobic systems.     

保试达(GLA)防除香蕉园杂草的药效及其对杂草群落的动态影响

通过田间试验研究新型膦酸类除草剂保试达(dufosinate-ammonium,GLA)防除香蕉园杂草的药效、杀草谱、安全性以及杂草群落次生演替动态,共设保试达200,250,300g/666.7 m2,克芜踪250 g/666.7 m2,百速顿250g/66.7 m2和清水对照6个处理.结果表明,保试达防除香蕉园杂草的药效均比克芜踪、百速顿好,防效的差异达极显著水平;保试达对优势杂草小飞蓬[Gonyza canadensis(L.)Cronq]防效达到100%;各处理对香蕉主茎植株无任何药害.但对香蕉基部蘖芽伤害水平达3～4级;处理试验45 d后,克芜踪处理的杂草群落多样性的丰富度、均匀度、密度-类群等指数显著区别于3个浓度的保试达试验处理,各处理的群落问相似性指数差异十分显著.综合分析可得,保试达250～300g/66.7 m2对香蕉园恶性和抗性杂草有较好防效功能,对香蕉园杂草群落次生演替有显著抑制作用.     

20％草铵膦AS对棉田杂草的防效

20％草铵膦AS按照有效成分用量450～1800g·hm^-2进行棉花行间定向喷雾处理,其对棉田杂草的田间防效优于对照药剂41％草甘膦异丙胺盐AS1230g·hm^-2。该药剂不仅除草速度快,而且持效期长,能有效防除棉田多种常见杂草,且对棉花幼苗无不良影响。     

免耕直播水稻杂草防除技术研究

在不同地区开展免耕直播杂草防除技术的试验和示范。2005年筛选出免耕直播稻田杂草防除最佳除草剂组合HC2（41％农达AS、38％苄·二氯WP、10％千金EC）;2006年HC2在浙江和湖北的超级稻免耕直播田示范,结果表明,对国稻1号田杂草千金子、异型莎草、鸭舌草和陌上菜的密度防效和植株鲜重防效达到优级水平（≥90％）,对国稻6号田杂草稗草、千金子、异型莎草和陌上菜的密度防效和植株鲜重防效达到极优水平（≥95％）。HC2对国稻1号和国稻6号的生长无不利影响,获得了较高产量。国稻1号在浙江海宁达到9510kg／hm^2,国稻6号实收产量达到6780kg／hm^2。     

稻作区灌溉水流传播的杂草种子与稻田土壤杂草种子库的关系

选择典型稻作区,对灌溉水流传播的杂草种子的种类和数量进行取样调查,并与田埂、灌溉水渠周围生境、下茬麦田的杂草群落及稻田土壤杂草种子库进行比较分析,以研究自然条件下灌溉水流传播的杂草种子与土壤杂草种子库及其他生境杂草群落间的相互关系。 有14科21种杂草种子随灌溉水流输入稻田,这些杂草种子主要隶属禾本科、报春花科、藜科、蓼科等。土壤杂草种子库中共检出19科41种杂草种子,含有所有其他生境中杂草的种子。灌溉水流传播的杂草种子与田埂上、灌溉水渠周围生境、下茬麦田杂草群落及稻田土壤种子库的杂草群落间相似性较高,Sorensen指数均在0.5以上。     

不同药剂处理对水田除草的效果分析

针对梅河口市水田杂草种类繁多、分布广、密度大的现状,选取5种混合药剂进行除草效果对比试验,结果表明:丁草胺加吡.扑.西混剂除草效果好,产量在各个处理中最高,且对水稻安全,建议在泽泻、慈菇较多的田块使用。     

甜菜田除草剂药效筛选试验

除草剂金都尔乳油和禾耐斯乳油应用直播甜菜前的土壤处理,除草效果试验结果表明,对禾本科杂草防治效果较好,平均防效为83.97%。两种药剂对双子叶杂草的总防效最好的浓度分别是金都尔600倍,禾耐斯960倍。同时禾耐斯除草剂总防效优于金都尔除草剂。     

向日葵田除草剂除草试验初报

对向日葵田杂草进行调查并试用除草剂除草。结果表明禾本科杂草占杂草总数的74%;播后苗前施药,64%踏青和50%乙草胺除草效果分别为96.9%和85.9%,对向日葵安全;苗后施药,5%精喹禾灵、12.5%拿扑净和15%精稳杀得对禾本科杂草防效达95%以上,但对阔叶杂草防效很低,对向日葵安全。