Enhanced degradation of atrazine under field conditions correlates with a loss of weed control in the glasshouse

Enhanced degradation of atrazine has been reported in the literature, indicating the potential for reduced residual weed control with this herbicide. Experiments were conducted to determine the field dissipation of atrazine in three cropping systems: continuous Zea mays L. (CC) receiving atrazine applications each year, Gossypium hirsutum L.-Z. mays rotation (CCR) receiving applications of atrazine once every 2 years and a no atrazine history soil (NAH). Subsequent laboratory and greenhouse experiments were conducted with soil collected from these cropping systems to determine atrazine degradation, mineralization and residual weed control. Field dissipation of atrazine followed first-order kinetics, and calculated half-life values for atrazine combined over 2003 and 2005 increased in the order of CC (9 d) = CCR (10 d) < NAH (17 d). Greenhouse studies confirmed that the persistence of atrazine was approximately twofold greater in NAH soil than in CC or CCR soil. Biometer flask mineralization studies suggested that enhanced degradation of atrazine was due to rapid catabolism of the s-triazine ring. Glasshouse efficacy studies revealed a loss of residual weed control in CC and CCR soil compared with NAH soil. These data indicate that, under typical Mississippi Delta field conditions and agronomic practices, the persistence of atrazine may be reduced by at least 50% if the herbicide is applied more than once every 24 months. Glasshouse studies suggest that under these conditions a loss of residual weed control is possible.     

紫花苜蓿田春季阔叶杂草除草剂筛选及安全性评价

为明确适用于紫花苜蓿田防除春季阔叶杂草的除草剂,本研究通过室内和田间试验筛选了对紫花苜蓿安全且对春季阔叶杂草防效好的除草剂。室内试验表明,供试的11种除草剂中仅有唑草酮、吡草醚、乙羧氟草醚等3种除草剂对紫花苜蓿具有较好的安全性。通过田间试验发现,40%唑草酮WG 30～66 g/hm²(有效成分用量,下同)和10%乙羧氟草醚ME 75～90 g/hm²处理对春季阔叶杂草具有较好的防治效果,株防效为83.68%～97.32%,鲜重防效为73.18%～95.62%,且对紫花苜蓿有较好的安全性,增产12%以上。综上所述,在紫花苜蓿返青期进行唑草酮和乙羧氟草醚处理可用于紫花苜蓿田春季阔叶杂草防除,具有较好的应用前景。     

Cross-resistance pattern and alternative herbicides for Cyperus difformis resistant to sulfonylurea herbicides in Korea

A Cyperus difformis L accession from Chonnam province, Korea was tested for resistance to the sulfonylurea herbicide, imazosulfuron. The accession was confirmed to be resistant (R) and was cross-resistant to other sulfonylurea herbicides, bensulfuron-methyl, cyclosulfamuron and pyrazosulfuron-ethyl, the pyrimidinyl thiobenzoate herbicide, bispyribac-sodium, and the imidazolinone herbicide imazapyr, but not to imazaquin. Multiple resistance was tested using twelve herbicides with target sites other than acetolactate synthase (ALS). The R biotype could be controlled by other herbicides with different modes of action such as butachlor, carfentrazone-ethyl, clomeprop, dithiopyr, esprocarb, mefenacet, oxadiazon, pretilachlor, pyrazolate and thiobencarb, applied to soil at recommended rates. Several sulfonylurea herbicide-based mixtures can control both the R and S biotypes of C difformis, except sulfonylurea plus dimepiperate, molinate or pyriftalid, and pyrazolate plus butachlor. Although mixtures of sulfonylurea herbicides might be more effective, they should be avoided and used only in special cases. In terms of in vitro ALS activity, the R biotype was 1139-, 3583-, 1482-, 416-, 5- and 9-fold more resistant to bensulfuron-methyl, cyclosulfamuron, imazosulfuron, pyrazosulfuron-ethyl, bispyribac-sodium and imazapyr, respectively, than the S biotype. The in vivo ALS activity of the R biotype was also less affected by the sulfonylurea herbicides, imazosulfuron and pyrazosulfuron-ethyl, than the S biotype. Results of in vitro and in vivo ALS assays indicated that the resistance mechanism of C difformis to ALS inhibitor herbicides was primarily due to an alteration in the target enzyme, ALS. Greenhouse experiments showed delayed flowering and reduced seed production of the R biotype, which could possibly result in reduced fitness. This unusual observation needs to be confirmed in field situations.     

4种茎叶处理除草剂对半夏田杂草的防除效果

为有效解决半夏田草害问题, 选择4种茎叶除草剂进行半夏田杂草防除田间药效试验。结果表明:10%乙羧氟草醚EC 50~60 mL/667m2 (制剂用量,下同)处理与240 g/L乳氟禾草灵EC 20~30 mL/667m2处理能有效防除半夏田金腰箭、辣子草、土荆芥、金荞麦、紫花香薷、针筒菜、尼泊尔蓼等阔叶杂草, 且对半夏安全, 药后21 d对阔叶杂草株防效、鲜重防效均达90%以上, 与禾本科除草剂8.8%精喹禾灵EC 40 mL/667m2或108 g/L高效氟吡甲禾灵EC 30 mL/667m2搭配使用对半夏田大部分杂草能实现较好防除。但两种阔叶除草剂持效期较短(30 d左右), 生产上可根据施药后期田间杂草发生情况, 采用人工拔除或进行第2次化学防除; 施药应避开中午高温时刻, 以免造成此类阔叶除草剂药害。研究结果可为半夏田除草剂的合理选择和应用提供科学依据。     

红花苗后除草剂筛选及安全性评价

本研究通过室内盆栽和田间试验相结合的方法筛选出对红花苗后安全且对阔叶杂草防效好的除草剂。室内盆栽试验从12种除草剂中初步筛选出30%草除灵SC、50 g/L双氟磺草胺SC、15%噻吩磺隆WP、12%砜嘧磺隆OD 4种对红花较为安全的除草剂。田间验证试验评估了它们对红花的安全性和除草效果,得出15%噻吩磺隆WP有效剂量36 g/hm~2对红花生长安全,且对红花田阔叶杂草防效最好。在田间验证试验的基础上,继续进行田间剂量优化试验确定合适的施用剂量范围,试验结果表明15%噻吩磺隆WP有效剂量27～36 g/hm~2对红花安全,株高抑制率小于15%,同时对田间阔叶杂草防效好。因此,红花田苗后除草可选用15%噻吩磺隆WP,推荐有效成分使用剂量27～36 g/hm~2;该药剂具有重要的应用前景。     

红花苗前除草剂筛选及安全性评价

本研究通过室内外试验评估了12种苗前除草剂对红花的安全性和除草效果。盆栽试验表明,50%乙草胺EC有效剂量675～1 350 g/hm~2,33%二甲戊灵EC 495～990 g/hm~2,960 g/L精异丙甲草胺EC 675～1 350 g/hm~2,24%乙氧氟草醚EC 60～180 g/hm~2,30%吡氟酰草胺SC 54～162 g/hm~2,250 g/L噁草酮EC 270～540 g/hm~2,50%丙炔氟草胺WP 45～90 g/hm~2,对红花生长抑制相对较小,鲜重抑制率基本上低于20%。田间对上述除草剂及其混用的安全性进行了测定,结果表明,960 g/L精异丙甲草胺EC 900 g/hm~2+250 g/L噁草酮EC 450 g/hm~2对红花生长抑制较小,与对照差异不显著,其他除草剂单独使用或混配使用对红花苗前期生长均有一定的抑制作用,但对叶色、株型等无明显影响,整体药害程度较轻。调查表明,除草剂混配使用较除草剂单用对杂草控制作用更好。     

3种茎叶处理除草剂在胡麻田的最佳施药期研究

为了筛选出对胡麻安全、对杂草防效优良的茎叶除草剂最佳喷施时期,田间测定了400 g/L 2甲·溴苯腈EC 1 500 mL/hm~2、56%2甲4氯钠SP 1 200 g/hm~2和40%2甲·辛酰溴EC 1 275 mL/hm~2在不同时期喷施对胡麻生长发育的影响及对田间杂草的防效。通过对胡麻株高、鲜重、产量及控草效果综合分析看出：400 g/L 2甲·溴苯腈EC在胡麻株高5 cm、56%2甲4氯钠SP在胡麻株高2.5～5 cm、40%2甲·辛酰溴EC在胡麻株高5～10 cm喷施,对胡麻株高的抑制作用均能在成熟期降至微弱或无影响,对胡麻鲜重的抑制作用均能提早减轻至微弱甚至无影响;胡麻生物产量分别较人工除草增加9.66%、-6.25%～-1.77%和7.19%～9.97%,胡麻籽粒产量分别较人工除草增加5.39%、-0.86%～-0.47%和-0.56%～5.45%;对阔叶杂草株防效分别达到81.82%、51.46%～73.88%和51.91%～67.21%,对阔叶杂草鲜重防效分别达到98.99%、88.96%～96.33%和91.26%～94.47%。可见,参试除草剂在上述时期喷施对...     

高粱田除草剂种类及施药方法筛选试验初报

为了筛选高效的高粱除草剂和适合的施药方式, 我们进行了高粱田间杂草化学防除药剂及施药方法筛选试验, 通过除草效果、产量和收益分析, 初步认为:施药方法上土壤封闭明显优于茎叶处理。土壤封闭剂中, 42%丁·异·莠去津SC、42%异丙草·莠SC除草剂对阔叶杂草和禾本科杂草防除作用优良, 鲜重防效均超过90%, 高粱产量虽低于人工除草, 但差异不显著, 减产幅度在1%以下; 使用这类药剂高粱生产的利润高于人工除草。茎叶处理剂中, 25%辛酰溴苯腈EC等除草剂对高粱生长影响较小, 对藜、反枝苋等阔叶杂草防效高, 高粱产量低于人工除草, 但高粱生产的利润高于人工除草。建议在高粱生产中使用这些除草剂。     

Evaluation of finger weeder safety and efficacy for intra-row weed removal in irrigated field crops

Increased demand for pesticide-free food and the development of herbicide-resistant weed populations have created a need for non-chemical weed-control tools. A candidate mechanical tool for controlling weeds in the seeding line (intra-row zone) is the finger weeder. This study thus aimed to evaluate the safety and weed-control efficacy of the finger weeder in various irrigated field crops. Eight field trials were conducted in processing tomato, sweet corn, sunflower, cotton, and beetroot over 2 years. The finger weeder treatments were applied as the sole weed-control method (single or double treatments) and in combination with herbicides. A mini meta-analysis was used to evaluate the overall effect of the finger weeder treatments on crop stand and yield and on weed control efficacy. Weed density in the control not treated with herbicides nor a finger weeder ranged between 2 and 62 weeds m⁻². The finger weeder treatments resulted in a significant reduction in weed density, which ranged between 40% and 90%. The weed density following the double finger weeder treatment was not significantly different from that for the conventional herbicide-based treatment (p = 0.32) and could therefore be considered as an effective environmentally friendly alternative. Furthermore, a single FW treatment integrated with herbicide application gave better weed control than the conventional herbicide treatment (p = 0.04). This treatment was safe for the crops with no significant stand (p = 0.19) or yield (p = 0.29) reductions compared to commercial treatment. The results of this study demonstrate the promise of the finger weeder as an effective tool within integrated weed management systems for conventional agro-systems. The tool offers a rational weed-control solution for sustainable systems under irrigation.     

2种增效剂对春玉米田除草剂的减量增效作用

为了明确2种增效剂对除草剂的减量效应,为除草剂科学减施及增效剂安全使用提供数据基础,2019年在西北荒漠绿洲生态区春玉米田,以38.5％硝·精·莠去津CS和26.7％噻隆·异噁酮SC作为茎叶处理剂,测定了激健和辉丰2种增效剂在不同施药剂量下的除草效果.结果 表明:在38.5％硝·精·莠去津CS 2310 mL/hm和2...     

不同除草剂对遍地黄金草坪杂草的控制效果及安全性

为了筛选出可用于防除遍地黄金草坪杂草的除草剂配方,经室内盆栽法测定不同除草剂茎叶处理对马唐、香附子、红花酢浆草的抑制效果及对遍地黄金的安全性后,进行药剂的田间试验,结果表明：25%啶嘧磺隆WG对总草的株防效和鲜重防效分别达到78.1%和80.5%,显著高于其他单剂处理的防效;56%2甲4氯钠盐SP对阔叶杂草的株防效和鲜重防效分别为85.4%和85.7%,高于其他单剂处理的防效;108 g/L高效氟吡甲禾灵EC对禾本科杂草的株防效和鲜重防效可达92.2%和92.6%,显著高于其他各处理的防效;108 g/L高效氟吡甲禾灵EC+56%2甲4氯钠盐SP混剂对禾本科杂草的株防效和鲜重防效分别为88.2%和91.1%,对阔叶杂草的株防效和鲜重防效分别为75.3%和78.2%,但对莎草科杂草的防效低;108 g/L高效氟吡甲禾灵EC+75%氯吡嘧磺隆WG混剂对禾本科杂草的株防效和鲜重防效较好,分别可达到85.4%和87.4%,对莎草科杂草的株防效和鲜重防效分别为71.9%和77.6%,但对阔叶杂草防效较低;56%2甲4氯钠盐SP+75%氯吡嘧磺隆WG混剂对阔叶杂草的株防效和鲜重防效分别可达到85....     

20种茎叶处理除草剂对冬小麦田宝盖草的防效及安全性测定

为筛选防除冬小麦田宝盖草的高效茎叶处理除草剂,本试验连续两年选取20种除草剂进行冬小麦田宝盖草的防除研究。结果表明,在小麦返青期施药,200 g/L氯氟吡氧乙酸异辛酯乳油、50%吡氟酰草胺水分散粒剂和10%苄嘧磺隆可湿性粉剂有效成分用量分别为210、120和60 g/hm~2时,药后40 d对宝盖草的株防效和鲜重防效均达到90%以上,并且对冬小麦表现安全,可大面积示范推广。     

Impact of Fusarium oxysporum on the holoparasitic weed Phelipanche ramosa: biocontrol efficacy under field-grown conditions

Under the changing agro-climatic conditions of western Europe, the parasitic weed Phelipanche ramosa infests host crops such as tomato, hemp, tobacco and oilseed rape at an increasing rate. A Fusarium oxysporum isolate (FOG), that had effectively reduced the parasite's incidence under controlled environmental conditions, was tested in different granular formulations (pesta granules, alginate pellets) on P. ramosa parasitising tobacco under field-grown conditions. FOG reduced number and biomass of P. ramosa shoots by between 50% and 70% in three consecutive years (2006–2008). A single pesta application did not show consistent results throughout seasons; 50% reduction of P. ramosa biomass (DM) in the first year could not be repeated in the following years (20–30%). An alginate formulation applied alone performed better. However, a combination of pesta granules with alginate pellets had the highest reliable control efficacy (60–70%) of all treatments in two seasons, compared with the untreated control. Fungal population counts in soil samples did not show a close correlation to biocontrol efficacy. To understand field performance of this biocontrol agent, additional glasshouse and laboratory studies were conducted using soil from the experimental site. The glasshouse study revealed some fungistatic effects of the field soil that partly explain the reduced efficacy (-40%) in the field compared with results obtained under controlled conditions. Results show the potential of FOG for P. ramosa control. Because formulation affected the biocontrol efficacy, it may be worthwhile to test how the delivery system can be changed in order to achieve increased disease development in the field.     

Secondary dispersal, spatial dynamics and effects of herbicides on reproductive capacity of a recently introduced population of Bromus sterilis in an arable field

An arable field was subdivided and subjected to either deep inversion ploughing or non‐inversion cultivation after viable seeds of Bromus sterilis had been sown into oilseed rape stubble. After sowing in isolated plots distributed within the field, sequences of cropping treatments for the establishment of two successive winter wheat crops were applied. Each subfield was split into an uphill and a downhill direction for soil cultivation. The field had a 10° slope. In the season following seed introduction, 2.6% of the introduced seeds had successfully germinated and established in the non‐inversion cultivation regime, when no effective graminicide was applied. Ploughing eradicated B. sterilis. Using differential global positioning system (DGPS) mapping of the whole field population, emerged plants were observed up to 8.7 m (uphill treatment) and 21.3 m (downhill treatment) of their initial source. The median distance seeds were transported was 2.3 m uphill and 4.8 m downhill. Post‐emergence application of the herbicide propoxycarbazone slightly reduced weed density and seed weight, and almost halved weed seed production. Application of fenoxaprop‐P‐ethyl was followed by higher density of plants, tillers and seeds of B. sterilis. Seed viability was unaffected by herbicide use. Thus, in the second wheat crop following seed rain, the weed population was dispersed more widely in the field, such that 20–30% of seeds were dispersed more than 5 m distance from the first year's foci of infestation. The relevance of soil cultivation to secondary dispersal of B. sterilis is discussed.     

40%氰净·乙·莠悬浮剂(益锄)防治玉米田杂草药效研究

田间试验表明益锄300~400g/667m2(华北地区)土壤封闭处理,能有效防除玉米田单子叶、双子叶杂草,药后40d防效90%以上。在推荐用量下,对玉米安全,并有明显的增产效果。     

氯氟吡啶酯对稻田杂草的室内除草活性及田间药效评价

氯氟吡啶酯是美国陶氏益农公司最新研制开发的芳基吡啶甲酸酯类除草剂.为了明确其在水稻田的应用技术,采用温室盆栽法测定了氯氟吡啶酯对稻田主要杂草的防效以及对8个水稻品种的安全性,同时开展了田间药效评价试验.温室测定结果表明,氯氟吡啶酯对鸭舌草、鳢肠、耳基水苋、碎米莎草、异型莎草和稗均有较好的除草活性,对千金子的除草活性相对...     

A degree-day concept for estimating degradation time under field conditions

Development of degradation rate information for crop protection products in soil is typically a time consuming and costly process. Therefore, development of methodology that would allow extrapolation of limited degradation information to wider field conditions in a predictive fashion would be desirable. This study presents an approach that uses a modified heat unit model to estimate organic compound degradation time using limited datasets. The model requires daily soil or air temperature and volumetric water content. Predictions based on the model for three different compounds in five different field studies were within 80% of measured values based on soil analysis. Results from this research indicate that the model was able to predict compound half-life values across all sites with r2 = 0.99.