Development of herbicides for paddy rice in Japan

The history of the development of herbicides for mechanized paddy rice production in Japan can be characterized by a combination of products with several ingredients, by large availability in formulation, and by application methods for labor saving in accordance with natural and social conditions of the country, for instance, around 40% of national land located in hilly and mountainous areas, small size paddy fields consolidated in approximately 0.3 ha on average and so on. As for combination products, one‐shot herbicides that can control both annual and perennial weeds, including grasses, sedges and broadleaved weeds, mainly with sulfonylureas have been a major means of rice production since the 1980s. One‐shot herbicides have been improved by using newly developed chemicals with excellent herbicidal efficacy, such as acetolactate synthase (ALS), 4‐hydroxyphenylpyruvate dioxygenase (4‐HPPD), protoporphyrinogen oxidase (PPO) and very‐long‐chain fatty acid elongase (VLCFAE) inhibitors, and by combining ingredients that are effective against sulfonylurea‐resistant (SU‐R) biotypes of lowland weeds. The latest type of one‐shot herbicides can control noxious species such as Eleocharis kuroguwai as well as other ordinal species. Regarding herbicide formulation, “1 kg granule,” “Jumbo,” “Flowable,” “Diffusion granule” and so on have been developed to save farmers the troubles of applying herbicides. As for application methods, “at‐transplanting application,” “at‐irrigation inlet application” and utilization of radio‐controlled helicopters or boats were put into practical use as labor‐saving technology. As a result, farmers were spared the severe hand‐weeding work under blazing heat during the summer season. Japan Association for Advancement of Phyto‐Regulators (JAPR) have promoted and contributed to the development of herbicides through collaboration with agrochemical companies and research organizations since it was founded in 1964. In this paper, I explain the development progress of herbicide using materials on the mode of action, the trend of one‐shot herbicides, the feature of a labor‐saving formulation and the working hours for weed management in rice production.     

Development and promotion of laborsaving application technology for paddy herbicides in Japan

Total labor time on paddy rice has been decreasing year by year with the development and introduction of appropriate herbicides, especially ‘one‐shot' herbicides. However, in the case of application of granules, it is still difficult for a farmer to apply herbicides while carrying heavy power backpack sprayers. New formulation recipes and different application technology such as a throw‐in type formulation on jumbo granules or flowable has improved heavy workloads in comparison with granule application by using heavy power backpack sprayers. In addition, other advantageous points such as application volume and elimination of the drift problems of this new application technology were introduced and confirmed. As a result of this introduction, these formulations were used in 830 000 ha and reached 30% of the total treatment area in paddy rice in 2000.     

Biological Control of Lantana

Abstract

Experiments conducted at the International Rice Research Institute (IRRI) in the Philippines, showed that all commonly marketed formulations and derivatives of 2,4-D and MCPA were equally effective in controlling barnyard grass [Echinochloa crusgalli (L.) Beauv.] and other annual weeds in transplanted rice (Oryza sativa L). In the Philippines, these phenoxy acid herbicides cost US$2.50/ha as liquid formulations and US$5.50/ha as granular formulations. These low-cost herbicides provide excellent alternatives to hand weeding in transplanted tropical rice. Other herbicides which can control weeds before or after the weeds emerge are more expensive than 2,4-D or MCPA. Some of these selective herbicides, such as butachlor and TCE-styrene + 2,4-D, are in the Philippine market. Their prices vary from US$8 to US$12/ha.

For direct-seeded flooded rice, granular formulations of several new herbicides, such as butachlor, benthio-carb and C-288 (chemistry not yet disclosed), were highly selective in controlling barnyardgrass and other annual weeds under tropical conditions. C-288 controls algae in addition to annual weeds in direct-seeded flooded rice. Of these three promising herbicides, only butachlor is marketed in the Philippines at US$8/ha. For upland rice, the chemicals which look promising are butachlor, benthiocarb and fluorodifen. Butachlor liquid is available to rice farmers in Asia at about US$16/ha. These herbicides provide an excellent alternative to hand weeding. Generally a complete job of weed control in upland rice requires more than one hand weeding.     

苗期水分管理对水稻分蘖及除草剂控草效应的影响

稻田除草剂大量及高频使用对农作物安全、土壤及水体环境构成了严重威胁,使得除草剂减量使用刻不容缓。水稻机插田药后长时间保水可显著抑制杂草,以此可减少除草剂用量,但长时间保水会导致水稻发育受限。盆栽试验表明,无论是否喷施除草剂30%苄嘧·丙草胺乳油,杂草发生随保水时长增加而减少,且喷施除草剂对杂草防除具显著效果。田间试验表明,稻田施用30%苄嘧·丙草胺乳油100 mL/667m~2后,药后保水7 d时的水稻分蘖及抑草的综合效应达到最佳。     

Weed control in direct-seeded lowland rice under poor water control conditions

Several herbicides applied singly and in combination were evaluated for weed control and for their effects on crop yield in direct-seeded lowland rice under poor water management conditions characteristic of the conditions in which lowland rice is grown by most farmers in West Africa. Several herbicides including cyperquat at 3.0 kg/ha, a mixture of cyperquat and 2,4-D at 2.0 + 0.5 kg/ha, bentazon at 2.0 kg/ha and avirosan satisfactorily controlled sedges in the 3-year study. Crop yield was consistently high in plots where weeds were controlled with post-emergence application of MCPA + propanil at 1.0+1.7 kg/ha, propanil + thiobencarb 2.2+1.2 kg/ha, oxadiazon 1.5 kg/ha, bentazon 2.0, granular 2,4-D at 1.0 kg/ha, and a pre-emergence application of bifenox at 2.0 kg/ha. Crop yields in plots treated with these herbicides were generally better than with two hand-weedings.     

An integrated approach to weed management practices in direct-seeded rice under zero-tilled rice–wheat cropping system

An increasing water crisis as well as shortage of farm labor farmers in many Asian regions is forcing a shift from puddled transplanted rice to direct-seeded rice. The weeds, however, are a major constraint to the production of direct-seeded rice. In this perspective, a field study was carried out to evaluate various pre- and post-emergence herbicides and different possible integrated weed management practices in zero-till direct-seeded rice. Weed infestation decreased the rice yield by near about 75%. Co-culture rice with Sesbania followed by (fb) pendimethalin fb 2,4-D effectively reduced the total weed population (65.1%) and biomass (86.7%) at 30 days after sowing (DAS). The lowest total weed dry biomass at 60 DAS was recorded from bispyribac-sodium+azimsulfuron-treated plot and such tank mix application of herbicide performed better against diverse weed flora as compared to a single herbicide. Higher yield and more profit from zero-till direct-seeded rice were obtained with the application of bispyribac-sodium+azimsulfuron herbicides as a tank mixture or an integrated approach through cowpea green-manuring fb 2,4-D+glyphosate fb bispyribac-sodium by effective management of versatile weed flora.     

Current status of biological control of paddy weeds in Vietnam

Rice is a staple food in Vietnam and accounts for > 7.7 × 10⁶ cultivated ha, which provide 35.5 × 10⁶ t of rice, of which 4.2 × 10⁶ t were exported in 2004. The enlargement of the cropping area and the enhancement of rice yield have rapidly increased the amount of agrochemicals, including herbicides, in crop production in Vietnam. From 1990–2003, the percentage of herbicides in total pesticides has increased ≈ 10-fold to 30.2%. In addition, the improper use of herbicides caused environmental hazards, unsafe agricultural products, and human health problems. Biological management integrated with traditional weed control techniques might help to reduce the dependence on synthetic herbicides and build eco-friendly, sustainable agricultural production in Vietnam. This paper reviews the efforts in establishing a strategy for biological management of weeds that was conducted in recent years by Vietnamese weed scientists. This has included cropping system management, water and soil management, integrated pest management, and utilization of plant allelopathy as major components of the strategy. Many plants with strong allelopathic potential can be a source for biological weed suppression and soil fertility improvement. The utilization of allelopathic properties in rice might also help to provide new rice cultivars with weed-suppressing characteristics.     

Effect of allelopathic rice varieties combined with cultural management options on paddy field weeds

BACKGROUND: A number of techniques, including cultural management, allelopathy and bioherbicide, have been considered as alternatives for synthetic herbicides, but successful weed control will require the careful integration of these multiple techniques. This study was conducted to assess the use of allelopathic rice varieties in combination with cultural management options on paddy weeds, in order to develop an allelopathy-based technique to reduce herbicide use in paddies. RESULTS: The weed-suppressive effects of the rice varieties tested varied highly with allelopathic trait, planting pattern and cultural management including planting density, flooding depth and duration and supply of nitrogen. Allelopathic rice varieties PI312777 and Huagan-1 demonstrated much stronger weed suppression than the non-allelopathic variety Huajianxian under the same planting pattern and cultural management. Their weed-suppressive effect was increased with cultural management options. In particular, if integrated cultural management options of allelopathic rice varieties included a low-dose (bensulfuron-methyl, 25 g AI ha(-1), a third of the recommended dose) herbicide application, the emergence and growth of most weeds found in paddy fields was completely controlled. No grain yield reduction for allelopathic varieties occurred under integrated cultural management options, whereas with the non-allelopathic variety a reduction of up to 45-60% was measurable even with the low-dose herbicide application. CONCLUSION: The allelopathic potential of rice varieties will likely have a great impact on paddy weed control if integrated with cultural management options and application of low doses of herbicides. Therefore, it is feasible to reduce herbicide input in paddies if allelopathic rice is grown under integrated cultural management practices.     

Weed problems and their management in rice fields of Malaysia: An overview

The available literature on weed problems and weed control in rice fields in Malaysia is reviewed and suggestions for future research are included. The problem of weed competition with rice is of great economic importance in the country because it causes a 10–35% reduction in grain yield. About US$4.10 million is spent annually on herbicides for rice alone, and this amounts to approximately 7% of the total expenditure on herbicides. The shift in methods of rice culture from transplanting to direct seeding has magnified the weed problem. The problem of weedy rice is particularly acute in the direct-seeding rice areas. Although a number of sulfonylurea herbicides (e.g. cinosulfuron, metsulfuron, bensulfuron and pyrazosulfuron) have been found to be suitable alternatives to the old herbicide 2,4-D, an integrated weed management program must be developed in order to reduce the problem of herbicide resistance in weeds. Weed control methods that are more friendly to the environment and affordable to farmers must be sought. Weed-competitive and allelopathic rice varieties must be produced. The problem of weeds in rice calls for systematic studies on biotechnological methods of control of weedy rice. Detailed studies on the biology and ecology of notorious rice weeds, particularly Oryza sativa L. (weedy rice), Echinochloa spp., Leptochloa chinensis (L.) Nees, Fimbristylis miliacea (L.) Vahl. and Limnocharis flava (L.) Buch. need to be done in order to formulate successful weed control measures.     

3种除草剂对水稻旱直播阔叶杂草防效及安全性研究

为明确不同除草剂茎叶处理对旱直播水稻田旱生阔叶杂草防除及安全性的影响,采用随机区组试验设计,选用30% 2,4-滴丁酸钠盐AS、84%氯酯磺草胺WG、480 g/L灭草松AS 3种除草剂在水稻4叶期、5叶期施用,施药后每间隔7 d测定杂草株防效、鲜重防效和水稻目测药害,同步测定水稻生长指标和抗逆酶活性。结果表明:30% 2,4-滴丁酸钠盐AS 900.0 g/hm2在水稻4叶期的杂草防效最佳,第28天杂草株防效及鲜重防效仍可达93.55%和96.42%,且对大龄鸭跖草防效显著,施药后水稻生长与人工除草相比无显著差异。叶片SOD、POD活性和MDA含量均先升后降,至施药后28 d恢复正常。30% 2,4-滴丁酸钠盐AS 900.0 g/hm2可高效防除阔叶杂草,该药剂在水稻4叶期和5叶期施用对旱直播水稻安全。     

Application of bispyribac‐sodium provides effective weed control in direct‐planted rice on a sandy loam soil

An increasing water crisis, as well as the unavailability and high cost of labor, in Pakistan has forced rice‐growers to plant rice directly into the field. However, severe weed infestation causes disastrous effects on the productivity of this rice system. In this study, three herbicides (pendimethalin, penoxsulam and bispyribac‐sodium) were evaluated for weed control in direct‐planted rice on a sandy loam soil. Weedy check and weed‐free plots were established for comparison. Weed infestation decreased the rice yield by 75.2%. However, the application of herbicides suppressed the weed infestation, with a simultaneous increase in the rice yield. The postemergence application of bispyribac‐sodium was the most effective herbicide in reducing the total weed density and dry weight over the weedy check, followed by penoxsulam and pendimethalin, respectively. Bispyribac‐sodium increased the number of productive tillers, 1000‐grain weight, number of grains per panicle and grain yield over the control, as well as improved the water productivity and economic returns of direct‐planted rice. The weeds' proliferation increased the number of unproductive tillers and decreased the plant height. In conclusion, the postemergence application of bispyribac‐sodium can be used effectively to control weeds, increase water productivity and improve the economic returns and yield of direct‐planted rice on a sandy loam soil in Pakistan.     

我国近年来水稻重大病虫害可持续控制技术重要研究进展——非化学控害技术研究

针对水稻病虫害防治中长期存在控害保产与生产无公害稻米矛盾比较突出的问题,研究提出了几种效果显著的非化学控害增产技术。其中,利用水稻遗传背景、对病虫抗感水平等差异显著的水稻品种多样性种植,控制稻瘟病的效果达42.12％～76.68％,抑制白背飞虱若虫数量增长效果明显,增产糯稻或优质稻600～1050 kg／hm²,平均增收约1 500元／hm²;稻鱼共育控制稻飞虱的效果为63.77％～86.89％,对纹枯病病株抑制率70.52％,控制稻田杂草效果为89.57％,平收获鲜鱼319.5～1 177.5 kg／hm²,水稻产量比对照区增产7.05％～10.11％;稻鸭共育控制稻飞虱效果63.73％～77.18％,控制稻螟效果30.11％,控制纹枯病效果19.33％～67.03％,对稻田杂草控制效果91.96％,减少施肥30.6％、农药59.3％,减少投入1 987.05元／hm²。     

THE HERBICIDAL ACTIVITY OF 2-AMINO-3-CHLORO-1,4-NAPHTHOQUINONE

Summary. An investigation was made of a now herbicide, 2–amino-3–chloio-1,4–naphthociuinone (ACNQ,), which appears to be promising for the control oi Echinochloa crus-galli (L.) Beauv. in transplanted paddy rice [ Oryza sativa L.).
In pot experiments in the glasshouse, seedlings of Echinochloa at different stages of growth were killed by ACNQ, at doses equivalent to 2–4 kg/ha (applied as granules) if they were submerged, but not if the shoots emerged above water. Activity was increased more by raising the level of water in the pot than by increasing the dosage. Emergent rice seedlings were little affected by ACNQ, up to 8 kg/ha, and the observed selectivity is considered to be due mainly to differences in plant height in relation to depth of water.
In laboratory experiments with rice seedlings grown without soil, the activity of ACNQ again increased with the depth of solution. Conversely, at a standard solution depth, there was a reduction in damage with advancing stage of growth, and the chemical had little effect once the leaf tip was above the solution surface.
The rate of leaching of ACNQ. through a sandy soil was slow and, at a dose of 2 kg/ha, persistence was about 15 days.
In evaluating new herbicides for paddy rice it is suggested that screening tests arc necessary on submerged as well as non-submerged plants.
Activité herbicide de la 2–amino-3–chloro-1,'4–naphtoquimne. I. Activité herbicide et profondtur de de l'eau     

Change in weed control studies of rice paddy fields in Korea

This paper was reviewed on the research status of weed control according to cultivating patterns of rice in Korea. Weed control study in a nursery bed was chiefly carried out to control the species of barnyardgrass at the times of machine transplanting. Propanil and nitrofen were applied successfully in wet-nursery beds, and chlornitrofen and pyrazolate/butachlor were also successfully applied in protected semi-irrigated rice nursery beds in the 1970s. Sequential application of herbicides in the mid-1980s has resulted in the end of hand weeding. In machine transplanting, basic research such as the selection of herbicides was conducted in the early 1970s, and its related research including crop injury, seedling age, and reaction of cultivars were done in the late 1970s to early 1980s. Effects of the continuous application of herbicides and its methods of labor saving for rice cultivation were studied in the mid to late 1980s. When the rice planting methods were newly established, such as transplanting when seedlings were 10-days-old and direct seeding from the early 1990s, weed control research relating to herbicides was carried out (e.g. herbicide registration, crop injury, water management, appropriate application time, and neighboring application with insecticide). Weed control for the dill seeding of fields in wetted and reclaimed saline land have been experimented with, particularly in terms of the physio-ecological characteristics and the control of problematic weeds, and the resistance of weeds to herbicides was also investigated systematically.     

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.     

Performance of pyrazosulfuron-ethyl in non-puddled transplanted rainy season rice and its residual effect on growth of the succeeding crop in rice-wheat cropping pattern

Abstract

A study was carried out in sandy clay loam textured soil of Mymensingh, Bangladesh to evaluate weed control efficiency of pre-emergence herbicide pyrazosulfuron-ethyl either alone or in sequential application with post-emergence herbicide in transplanted rainy season rice under non-puddled strip-tilled (NPST) field condition and also to examine the residual effect of those herbicides on germination and growth of the subsequently grown wheat crop. Five treatment combinations of pyrazosulfuron-ethyl were tested against one weedy check and one weed-free check. The study revealed that NPST rice field was mostly infested by grass and sedge weeds and herbicide treatments offered a wide range of control (above 50% to 95%) on all types of weeds. Application of pyrazosulfuron-ethyl followed by (fb) orthosulfamuron fb butachlor plus propanil provided the most effective and economic weed control over two years of the study. Moreover, micro-plot bioassay study claimed germination and growth of subsequently grown wheat were not adversely affected by herbicides that were applied in rice. Therefore, application of pyrazosulfuron-ethyl followed by post-emergence herbicide could be effective and economic to control weeds in NPST rice under rice-wheat system, but proper rate and time of application should strictly be followed.     

Chemical weed control in rainfed upland rice in Nigeria

Abstract

Two field experiments on chemical weed control in Faro 41 upland rice (Oryza sativa L.) variety were conducted at a rainforest site near the National Cereals Research Institute, Amakama Substation in 1989 and 1990. The herbicides tested were a coformulated mixture of pretilachlor and dimethametryne at 1.5, 2.0 and 2.5 kg a.i./ha, a co‐formulated mixture of piperophos and propanil applied at 3.16 and 3.95 kg a.i./ha, and Oxadiazon at 1.0 kg a.i./ha. Two hand weedings and a ‘no weeding’ treatment were included. The herbicides were applied 5 days after planting. All were safely selective to the crop. Most provided adequate weed control through 8–12 weeks after planting. Weeds controlled included Cynodon dactylon, Commelina benghalensis, Dlgitaria horizontalis, Eleusine indica, Panicum maximum and Pennisetum purpureum as grass weeds. The broadleaf weeds were Emilia sonchifolia, Ageratum conyzoides, Portulaca oleraceae, Richardia brasiliensis and Ipomoea Involuncrata. The sedges Mariscus alternifolius and Cyperus esculentus were encountered in the plots. Pretilachlordimethametryne at 2.5 kg a.i./ha had the best weeding score. Twoyear average grain yields of 1.7–2.6 t/ha were obtained from the herbicide treatments. With only 0.4 t/ha from the unweeded treatment, yield losses of more than 80% were recorded.     

Breeding of commercially acceptable allelopathic rice cultivars in China

BACKGROUND: One promising area of paddy weed control is the potential for exploiting the weed‐suppressing ability of rice. This study was conducted to develop commercially acceptable allelopathic rice cultivars using crosses between allelopathic rice variety PI312777 and commercial Chinese cultivars (N2S, N9S, Huahui354, Peiai64S and Tehuazhan35), and to assess their weed suppression and grain yield in paddy fields in relation to their parents. RESULTS: There was a positive dominance in the crosses Huahui354 × PI312777 and N2S × PI312777 but recessive or negative dominance in N9S × PI312777, Peiai64S × PI312777 and Tehuazhan35 × PI312777. Huahui354 × PI312777 and N2S × PI312777 showed stronger weed suppression than their parents and other crosses. Finally, an F₈ line with an appearance close to Huahui354 and a magnitude of weed suppression close to PI312777 was obtained from Huahui354 × PI312777. This line, named Huagan‐3, was released as a first commercially acceptable allelopathic rice cultivar in China. The grain yield and quality of Huagan‐3 met the commercial standard of the local rice industry. Huagan‐3 greatly suppressed paddy weeds, although suppression was influenced by year‐to‐year variation and plant density. There was no certain yield reduction in Huagan‐3 even under a slight infestation of barnyard grass in paddy fields. CONCLUSION: The successful breeding of Huagan‐3 with high yield and strong weed suppression may be incorporated into present rice production systems to minimise the amount of herbicide used. Copyright © 2011 Society of Chemical Industry     

Weeding techniques in transplanted and direct wet-seeded rice in Pakistan

Field studies were undertaken to explore the weed management strategies for transplanted and direct wet-seeded rice in the Dera Ismail Khan district of North-west Frontier Province, Pakistan. The experimental design was a randomized complete block with a split plot arrangement. The main plots consisted of two planting techniques (transplantation and direct seeding), while weed control practises assigned to the subplots included the use of the granular herbicide Sunstar 15WG (ethoxy sulfuron), Machete 60EC (butachlor), conventional hand weeding, and the weedy check (untreated control). Data were recorded on weed dynamics and the agronomic parameters of the rice crop. Economic analyses on the data were also run. The weed density and biomass were lower in the transplantation plots than the direct-seeding plots. The herbicides ethoxy sulfuron and butachlor reduced the density over the weedy check, with a density comparable to hand weeding in 2002, but slightly higher in 2003. As a result of weed management by hand weeding and herbicides, the paddy yield and its components were significantly higher for the transplanted method compared to the direct-seeded method. The comparable yield of herbicides with hand weeding offers an option for the use of herbicides as an alternative management tool. In light of our findings, it is concluded that for good economic returns, rice crops may be transplanted rather than direct-seeded. The herbicides ethoxy sulfuron and butachlor offer a weed control cover comparable with hand weeding under the transplantation method, while butachlor is good for controlling weeds even under the direct-seeded conditions in the agroclimatic conditions of the area.     

我国农田杂草治理技术的发展

我国稻、麦、玉米、大豆及棉花等主要农作物农田杂草有580种,属于危害重而又难于防除的有17种,受杂草危害较重的农田有3 580万hm²,年平均受草害减产12.3％～16.5％(加权平均)。自1980年以来,全国化学除草面积以年增200万hm²的速度扩大,农田化学除草面积从20世纪70年代早期不到100万hm²扩大到近年来6 000万hm²。本文概述了我国农田主要作物杂草的发生危害、化学除草剂应用现状及其综合防治进展,并提出今后杂草防除的设想与建议。