Prevalence of herbicide‐resistant weed species in Malaysian rice fields: A review

The management of weeds in Malaysian rice fields is very much herbicide‐based. The heavy reliance on herbicide for weed control by many rice‐growers arguably eventually has led to the development and evolution of herbicide‐resistant biotypes in Malaysian rice fields over the years. The continuous use of synthetic auxin (phenoxy group) herbicides and acetohydroxyacid synthase‐inhibiting herbicides to control rice weeds was consequential in leading to the emergence and prevalence of resistant weed biotypes. This review discusses the history and confirmed cases and incidence of herbicide‐resistant weeds in Malaysian rice fields. It also reviews the Clearfield Production System and its impact on the evolution of herbicide resistance among rice weed species and biotypes. This review also emphasizes the strategies and management options for herbicide‐resistant rice field weeds within the framework of herbicide‐based integrated weed management. These include the use of optimum tillage practices, certified clean seeds, increased crop competition through high seeding rates, crop rotation, the application of multiple modes of action of herbicides in annual rotations, tank mixtures and sequential applications to enable a broad spectrum of weed control, increase the selective control of noxious weed species in a field and help to delay the resistance evolution by reducing the selection pressure that is forced on those weed populations by a specific herbicidal mode of action.     

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.     

我国水稻田杂草抗药性研究进展

水稻是我国最主要的粮食作物之一,杂草的危害严重影响了水稻的产量与品质。化学防除仍然是治理水稻田杂草最有效的途径。目前我国水稻田稗属杂草、千金子、马唐、雨久花、野慈姑、异型莎草、耳叶水苋、眼子菜、节节菜、萤蔺等多种杂草对二氯喹啉酸、五氟磺草胺、氰氟草酯、噁唑酰草胺、苄嘧磺隆、吡嘧磺隆、双草醚、噁草酮、乙氧氟草醚等多种常用除草剂产生了抗药性。面对日趋严重的水稻田抗药性杂草的危害,对抗药性杂草进行深入系统的研究以达到科学防治的目的显得尤为重要。本文总结了我国水稻田抗药性杂草的抗药性水平、靶标酶抗药性机理、代谢酶抗药性机理和其他抗药性机理,归纳了抗药性杂草的交互抗性、多抗性发生情况以及抗药性治理现状,分析了我们在杂草抗药性研究与治理方面面临的问题。     

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...     

The response of ACCase-resistant Phalaris paradoxa populations involves two different target site mutations

Phalaris paradoxa (awned canary-grass) is an aggressive annual winter weed in wheat and other arable crops that is controlled mainly by ACCase-inhibiting herbicides: cyclohexanediones (DIMs), aryloxyphenoxypropionates (FOPs) and phenylpyrazolines (DENs, e.g. pinoxaden). The selection pressure imposed on the weed populations by repeated use of these herbicides has resulted in the evolution of increased numbers of ACCase-resistant populations of P. paradoxa in Israel and other countries. Two populations, Revadim (RV) and Mishmar Ha'emek (MH) that were exposed to differing weed and crop management tactics were investigated. Both populations were highly resistant to all FOPs, pinoxaden and cycloxydim, but responded differently to some DIMs. RV plants exhibited much higher resistance to tralkoxydim than MH plants, while showing similar low levels of resistance to tepraloxydim and clethodim. Both populations were equally susceptible to graminicides with other modes of action. The mutations responsible for the observed resistance were identified using PCR-RFLP and by sequencing the carboxyl transferase domain of the chloroplastic ACCase gene. RV plants possess a substitution of Asp₂₀₇₈ to Gly, whereas in MH population a mixture of Ile₂₀₄₁ to Asn or Asp₂₀₇₈ to Gly was found. Our study demonstrates that lack of herbicide and crop rotation may result in the evolution of diverse target site mutations and differential response of the whole plant to ACCase inhibitors.     

五氟磺草胺与吡氟酰草胺的联合作用及对水稻移栽田杂草的防效

吡氟酰草胺属于类胡萝卜素生物合成抑制剂类除草剂,为明确其与乙酰乳酸合成酶抑制剂类除草剂五氟磺草胺复配的联合作用及复配剂对水稻移栽田杂草的田间防效,采用温室盆栽法,评价了二者复配后的除草活性及联合作用类型,并通过田间小区试验评价了复配制剂对水稻田杂草的防效和对水稻的安全性。温室盆栽试验结果表明：五氟磺草胺与吡氟酰草胺复配后对稗、马唐、异型莎草及鳢肠的活性均表现为相加作用,二者复配的合适配比(质量比)范围为(1～2):(5～10)。田间小区试验结果表明,于水稻移栽后8 d茎叶喷雾处理,300 g/L五氟磺草胺·吡氟酰草胺(1:5)悬浮剂对水稻生长安全,且对水稻田稗、异型莎草、耳叶水苋及丁香蓼有良好的防效：在有效成分用量112.5～135.0 g/hm²剂量下,药后35 d,复配悬浮剂对上述杂草的总草株防效和总草鲜重防效分别为93.8%～95.8%和94.1%～96.1%,尤其是显著提高了对较难防除型杂草耳叶水苋及丁香蓼的防效,整体防效显著高于对照两个单剂处理及当地常规用药22%苄嘧磺隆·乙草胺可湿性粉剂处理。五氟磺草胺与吡氟酰草胺复配能够在扩大杀草谱的同时提高防效,且...     

A stochastic simulation model for evaluating the concept of patch spraying

The long-term economic benefits of `patch' spraying are likely to be related to the initial spatial distribution of the target weeds, the demographic characteristics of the species and the weed control and crop husbandry practices to which they are subjected. This paper describes a stochastic simulation model developed to investigate the interaction between weed seed dispersal and patch spraying. Simulated weed plant and seed populations are generated and compared with data from field observations. Lloyd's Patchiness index is used to quantify the patchiness of the weed density distribution, and the parameter k of the negative binomial distribution is used as a measure of distribution shape. A method of assessing the spatial scale of weed aggregation is proposed, in which spatial weed density information is transformed into the frequency domain, using a discrete two-dimensional Fourier transform. In this paper, we simulate `on/off' patch spraying (full or zero herbicide application rate). A quantitative analysis of the effects of sprayer resolution and weed seed dispersal range on the herbicide reduction and yield benefits from patch spraying is performed for three initial spatial seedbank distributions. The model is parameterized for the grass weed Alopecurus myosuroides Huds. Herbicide is applied in square areas (whose size is defined by the spatial resolution of the sprayer) in which mean weed density is greater than or equal to one plant m^–2. For a system conforming to this specification we show that for the control of A. myosuroides , it is unlikely that patch spraying would be profitable in the long term if the control area is larger than 6 m × 6 m. In some circumstances higher resolution may be required.     

Weed shoot morphology effects on competitiveness for light in direct-seeded rice

The effects of weed shoot morphology on competitiveness for light in rice ( Oryza sativa L.) have not been well described quantitatively and are difficult to study empirically. A rice:weed model was used to analyse the effects of weed leaf area densities (LAD; m² m^–3), leaf angles (as leaf light extinction coefficients, k _leaf) and maximum heights ( H _m, m) on growth and competition with rice. Weed morphologies were hypothetical but empirically based, as follows: LADs were skewed to the bottom or conical, k _leaf values varied from 0.2 (erectophile) to 0.8 (planophile), and H _m values were 0.5 H _R, 1 H _R and 1.25 H _R, where H _R was rice maximum height. Other parameters were equal to those of rice. Growth and competitiveness were evaluated using mature seed dry weights (g m^–2). Short weeds and weeds with conical LADs were weakly competitive, regardless of other traits. For other weed types, interference with rice was positively related to H _m, LAD skewness and more planophile leaves. All three traits were critical determinants of weed interference but no single morphological trait guaranteed competitiveness. All else being equal, weeds with highly skewed LADs produced the most seed dry weight. Planophile leaves were particularly beneficial for short weeds, giving over five times more seed dry weight than erectophile leaves.     

Enhanced effect of thiobencarb on bispyribac-sodium control of Echinochloa phyllopogon (Stapf ) Koss. in California rice (Oryza sativa L.)

Bispyribac-sodium {sodium 2,6-bis[(4,6-dimethoxy-2-pyrimidinyl)oxy] benzoate} has recently been introduced to California where it effectively controls Echinochloa spp. in rice ( Oryza sativa L.). However, biotypes of early watergrass ( Echinochloa oryzoides (Ard.) Fritsch) and late watergrass ( E. phyllopogon (Stapf ) Koss.) have evolved resistance to this herbicide. In 2001 and 2002, greenhouse and field experiments evaluated interactions between thiobencarb { S -[(4-chlorophenyl) methyl] diethylcarbamothioate} and bispyribac-sodium on resistant (R) and susceptible (S) late watergrass in California rice. Synergism was assessed using Colby's test and regression analysis. In the greenhouse, thiobencarb at 4480 and 5333 g ai ha⁻¹ synergistically reduced bispyribac-sodium GR₅₀ values on the R and S biotypes by 50–70% without increasing toxicity to rice. Synergism was also observed on S late watergrass in the field when 10 g ai ha⁻¹ bispyribac-sodium was mixed with 1120–2240 g ai ha⁻¹ thiobencarb. These effects could be related to interactions between thiocarbamates and enzymes in Phase I reactions of herbicide metabolism. This synergism results in better control at lower rates allowing a reduction in weed control costs, the herbicide load on the environment and a lower selection pressure towards resistant weed biotypes.     

不同除草剂对稻田杂草群落演替的影响

为了明确除草剂对稻田杂草群落演替的影响,2001～2004年,连续4年施用7种稻田除草剂控制移栽稻田杂草,每年调查稻田杂草的种类、密度和鲜重,分析稻田杂草种群的变化.结果表明：连续使用同一除草剂对稻田杂草群落演替影响显著,靶标杂草的优势度值与药剂使用年限存在显著的线性或非线性关系：Y=a＋bx或Y=ax^2＋bx＋c;非靶标杂草优势度值与药剂使用年限呈极显著正相关线性关系.不同药剂处理的杂草群落有一定的差异,连续使用二元复配除草剂,杂草群落的均匀度和多样性指数分别为0.40～0.43和1.57～1.84,明显低于单剂处理和对照区,田间主要杂草是陌上菜、水苋、千金子和水莎草,其杂草的鲜重显著低于其它处理.     

重庆地区稻田杂草安全高效防控技术与建议

重庆地区稻田杂草有33种,分属22个科,其中以莎草科和禾本科杂草种类最多.稻田优势杂草与耕地制度及栽培方式密切相关.冬季囤水田以牛毛毡、空心莲子草、异型莎草、野慈姑和浮萍为多;稻-油轮作田以猪殃殃、牛筋草、繁缕、看麦娘为多.根据稻田耕作类型科学施用有针对性的除草剂,并实行年度更换,以减少除草剂残留和杂草抗药性的产生;改进收割机械,加强适宜机收的水稻新品种选育,以减轻机械收获稻谷带来的落粒越年生秧苗防除难题.     

Intraregional and inter‐regional variability of herbicide sensitivity in common arable weed populations

The question on intraregional versus inter‐regional variability in herbicide sensitivity for weed populations is of major importance, both in extrapolation of model parameters and in herbicide zonal approval procedures. We hypothesised that inter‐regional variability in herbicide sensitivity for field populations would be the same as intraregional variability for regions with similar climatic conditions. Seeds of field weed populations were collected in a Danish, German and Polish region. Herbicide sensitivity was tested in dose–response experiments in the glasshouse with flufenacet and iodosulfuron (Apera spica‐venti), florasulam and tribenuron (Tripleurospermum inodorum), diflufenican, diflufenican + flurtamone and pendimethalin (Viola arvensis). ED₅₀ values and variance components of the ED₅₀ values were estimated to describe the influence of region, year and population. The regions accounted for a maximum of 26% of the variance and always less than the variance accounted for by individual populations. Sensitivity indices (SI₅₀) were calculated as the ratio between ED₅₀ of the test population and a reference population. There was considerable intraregional variability in SI₅₀ values and SI₅₀ values from a single region did not consistently differ from other regions. The large intraregional variability in herbicide sensitivity between populations, with no evidence of resistance, is of interest both for zonal evaluation of herbicides and resistance research. For practical weed management, we conclude that dose–response functions can be transferred between the study regions, for example for the common use in decision support systems with proper insurance for the control of less sensitive populations.     

Establishment of the baseline sensitivity and monitoring response of Papaver rhoeas populations to florasulam

In accordance with the EPPO guideline for the efficacy evaluation of plant protection products, resistance risk analysis PP 1/213(1), a method was established to determine the baseline sensitivity of key weed species to florasulam, a new triazolopyrimidine sulfonanilide herbicide for post-emergence control of dicotyledonous weeds in cereals. The aim of the baseline monitoring project was to understand the natural variation in response to florasulam of diverse populations of Papaver rhoeas at the time of product launch. The method entailed seed collection from representative agricultural areas throughout Europe. The seed was subjected to glasshouse tests where dose-response studies were conducted and ED80 values generated. This enabled a sensitivity index to be calculated for each country, giving an indication of the variation in P rhoeas response to florasulam in the populations tested.     

Improved management of Avena ludoviciana and Phalaris paradoxa with more densely sown wheat and less herbicide

Summary The effectiveness of crop competition for better weed control and reducing herbicide rates was determined for Avena ludoviciana and Phalaris paradoxa . Four experiments, previously broadcast with seeds of the two weeds in separate plots, were sown with three wheat densities, and emerged weeds were treated with four herbicide doses (0–100% of recommended rate). The measured crop and weed traits were first analysed across experiments for treatment effects. Grain yield and weed seed production data were then analysed using cubic smoothing splines to model the response surfaces. Although herbicide rate for both weeds and crop density for P. paradoxa had significant linear effects on yield, there was a significant non-linearity of the response surface. Similarly, herbicide rate and crop density had significant linear effects on weed seed production, and there was significant non-linearity of the response surface that differed for the weed species. Maximum crop yield and reduction in seed production of P. paradoxa was achieved with approximately 80 wheat plants m⁻² and weeds treated with 100% herbicide rate. For A. ludoviciana , this was 130 wheat plants m⁻² applied with 75% herbicide rate. Alternatively, these benefits were achieved by increasing crop density to 150 plants m⁻² applied with 50% herbicide rate. At high crop density, application of the 100% herbicide rate tended to reduce yield, particularly with the A. ludoviciana herbicide, and this impacted adversely on the suppression of weed seed production. Thus, more competitive wheat crops have the potential for improving weed control and reducing herbicide rates.     

双环磺草酮与氯氟吡啶酯复配的联合除草活性及对水稻的安全性评价

双环磺草酮是一种新型的对羟基苯丙酮酸双加氧酶抑制剂类除草剂,为明确其除草活性以及其与合成激素类除草剂氯氟吡啶酯复配后的除草效果,采用温室盆栽法研究了二者复配的联合作用类型,以及复配药剂在水稻与杂草之间的选择性,并进行了田间药效评价。温室盆栽试验结果表明:双环磺草酮与氯氟吡啶酯复配后使用,对供试杂草稗草、千金子、异型莎草及鸭舌草均呈现加成或增效作用;其中二者按照质量比5:1复配后的除草活性高于双环磺草酮单剂;复配药剂在供试水稻品种与杂草之间的选择性指数在28.72~54.81之间,与两种单剂相比,复配药剂对水稻的安全性均有提高。田间药效试验结果表明:双环磺草酮与氯氟吡啶酯复配扩大了杀草谱,对稗草、千金子、异型莎草及雨久花的株防效和鲜重防效在93.4%~100%之间,且对水稻安全;其中,田间复配用量为双环磺草酮有效成分120 g/hm^2、氯氟吡啶酯有效成分18 g/hm^2时效果最佳,对4种供试杂草的防效为97.1%~100%。     

Mutations of the ALS gene endowing resistance to ALS-inhibiting herbicides in Lolium rigidum populations

BACKGROUND: In the important grass weed Lolium rigidum (Gaud.), resistance to ALS‐inhibiting herbicides has evolved widely in Australia. The authors have previously characterised the biochemical basis of ALS herbicide resistance in a number of L. rigidum biotypes and established that resistance can be due to a resistant ALS and/or enhanced herbicide metabolism. The purpose of this study was to identify specific resistance‐endowing ALS gene mutation(s) in four resistant populations and to develop PCR‐based molecular markers. RESULTS: Six resistance‐conferring ALS mutations were identified: Pro‐197‐Ala, Pro‐197‐Arg, Pro‐197‐Gln, Pro‐197‐Leu, Pro‐197‐Ser and Trp‐574‐Leu. All six mutations were found in one population (WLR1). Each Pro‐197 mutation conferred resistance to the sulfonylurea (SU) herbicide sulfometuron, whereas the Trp‐574‐Leu mutation conferred resistance to both sulfometuron and the imidazolinone (IMS) herbicide imazapyr. A derived cleaved amplified polymorphic sequences (dCAPS) marker was developed for detecting resistance mutations at Pro‐197. Furthermore, cleaved amplified polymorphic sequences (CAPS) markers were developed for detecting each of the six mutant resistant alleles. Using these markers, the authors revealed diverse ALS‐resistant alleles and genotypes in these populations and related them directly to phenotypic resistance to ALS‐inhibiting herbicides. CONCLUSION: This study established the existence of a diversity of ALS gene mutations endowing resistance in L. rigidum populations: 1–6 different mutations were found within single populations. At field herbicide rates, resistance profiles were determined more by the specific mutation than by whether plants were homo‐ or heterozygous for the mutation. Copyright © 2008 Society of Chemical Industry     

THE GENETIC RESPONSE OF BARLEY TO DDT AND BARBAN AND ITS SIGNIFICANCE IN CROP PROTECTION

Summary. The response of eleven barley varieties to DDT and barban was assessed in field and glasshouse trials. Chlorosis following the application of DDT and minimal doses of barban is an all-or-nothing effect, whereas in apical inhibition there are several degrees of resistance. The criteria used to assess the eflect of barban on apical inhibition were fresh weight of seedlings, fertile tiller production at maturity and visual estimates of damage at the seedling stage and at maturity. Inheritance studies showed that resistance to the chlorosis reaction of both DDT and barban is controlled by single recessive genes independently inherited.
Resistance to apical inhibition, on the other hand, appears to be quantitatively inherited. When F₂ and F₃ segregating populations in the field were sprayed with barban, the proportion of resistant plants in successive generations was markedly increased.
The authors conclude that collaboration between plant breeder and pest control specialists could lead to a far more efficient control of weed, pest and pathogen by the development of varieties of crop plants with a high degree of tolerance to the chemical employed, especially under conditions where selectivity is narrow and delicate, such as in the control of other monocotyledonous plants in cereals.     

Co‐operative versus non‐co‐operative farmers' weed control decisions in an agricultural landscape

This study presents a simple landscape model of the influence of seed dispersal on weed population dynamics between fields. In the model, three fields are interconnected through weed seed dispersal, where seed might move with field equipment, in irrigation water or may be wind‐dispersed. The model is intended to characterise the impact of field‐level weed management decisions on landscape‐level weed population dynamics. Two simple scenarios were studied. The first simulates farmers adopting common effective methods of control on each of the three fields. In the second scenario, farmers manage the weed population independently on each of the three fields. In the first scenario, weed populations were driven to extinction as might be expected with uniformly high levels of weed suppression in each of the three fields. In the second scenario, when the two nearest fields in the sequence experienced control, the weed population was driven to extinction in the second field but not in the first where weed populations were able to survive in spite of high levels of suppression. The results suggest that control measures within a field may not adequately reflect their impact on weed population dynamics when between field seed movement occurs. Another important result is the importance of proximity and spatial arrangement of fields and the resulting influence on weed population dynamics within a field.     

Population structure of ALS-inhibiting herbicide-resistant Sonchus oleraceus in South Australia

Background

Annual sowthistle is a weed that is difficult to control in lentil crops in southern Australia due to a lack of herbicide options, widespread herbicide resistance and prolific production of highly mobile seed. This study investigates herbicide resistance in annual sowthistle in the Mid-North (MN) and Yorke Peninsula (YP) regions of South Australia, identifies and characterizes the mechanisms of acetolactate-synthase (ALS)-inhibitor resistance in this amphidiploid species, and combines this with analyses of population structure and gene flow.

Results

ALS-inhibitor-resistant annual sowthistle is widespread across the YP and MN of South Australia and is associated with a variety of Proline-197 mutations of the ALS gene, including leucine, alanine, arginine, serine, threonine and histidine. These mutations were found in different combinations on either of the two copies of the ALS gene. An additional 200 tissue samples were collected from across a single field on the YP and the ALS gene was sequenced for all these individuals. Different ALS-inhibitor resistance profiles were evident between mutation combinations and within mutation combinations, possibly mediated by differing subgenome assortment of the mutations, or altered gene experession of the two ALS homeologs. Population genetics analysis showed evidence of long-distance dispersal, resulting in highly mobile resistance genes, and multiple instances of resistance mutation evolution.

Conclusions

Continuing selection of Sonchus oleraceus populations with ALS-inhibiting herbicides has resulted in the accumulation of additional mutations within the ALS gene. New practices to control herbicide-resistant S. oleraceus should be examined, and control should focus on reducing seed set and dispersal to prevent the spread of emerging cases of resistance. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Implications of delayed Echinochloa spp. germination and duration of competition for integrated weed management in water-seeded rice

Summary Co-ordinating herbicide applications with the suppressive ability of the crop has the potential to improve weed control and optimize herbicide use in water-seeded rice. However, the successful integration of herbicide applications and crop development depends on the timing and duration of competition between rice and weeds. The critical period of competition between rice and Echinochloa species was examined in field and glasshouse experiments from 1996 to 2000. In 1999 and 2000, Echinochloa species seeded 30 days after rice in field experiments did not survive and rice yields were not reduced when plots were kept weed-free for 30 days or longer. In a basin experiment conducted in 1998, E. phyllopogon seeded with the crop was unaffected by light competition alone but the relative importance of shading by the crop increased when E. phyllopogon was seeded after rice. Management strategies that delay the germination or growth of Echinochloa species might confer a competitive advantage to rice and reduce the need for herbicide applications. However, yields in the field experiments were reduced by at least 18% after only 30 days of competition in both years, suggesting that it may be difficult to integrate currently available herbicides with crop growth in water-seeded rice.