The Potential Use of Herbicides in Tropical Peasant Agriculture

Abstract

The possible effects of herbicide use by peasant farmers are examined. It is considered that herbicides could be used for bush clearing but that their use should not be encouraged at present. It is concluded that herbicides can be used to control perennial weeds, to protect cereal crops from witchweed and to reduce the seasonal peak of labour demand.     

呼伦贝尔盟农田杂草分布、发生规律与防治策略的研究

以生物测定及羧酸酯酶活性测定的方法,检测了上海地区菜缢管蚜对有机磷的抗药性。测定结果表明,金山群体对乐果、杀螟松和马拉硫磷的抗药性分别是梅陇的5.7、4.0和1.8倍。金山群体的羧酸酯酶活性高于梅陇。说明其抗性与羧酸酯酶活性增高有关。单个蚜虫的羧酸酯酶活性测定是检测抗性及抗性个体在群体内分布的一种既迅速又精确的方法。如把蚜虫的羧酸酯酶活性分成3类:低羧酸酯酶活性(OD<0.3)、中等羧酸酯酶活性(OD:0.3—0.5)和高羧酸酯酶活性(OD>0.6),则金山与梅陇种群低羧酸酯酶活性个体分别占8％、30％;中等活性个体分别占85％、68％;高活性个体分别占7％、2％。     

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.     

Resistance against uprooting in carrots ( Daucus carota) and annual weeds: a basis for selective mechanical weed control

Trials were carried out in order to investigate ways in which to achieve selectivity in mechanical weed control. The influence of soil type, uprooting angle and development stage on the uprooting force of some annual weeds and carrot was studied. Spergula arvensis L., Urtica urens L., Chenopodium album L. and carrot (Daucus carota L.) were sown in soil bins filled with four different soil types. The plants were uprooted when they had two true leaves. Soil type significantly influenced the uprooting force needed by all four species. The forces required to uproot U. urens and C. album differed significantly between peat and loamy sand. In loamy sand, Capsella bursa-pastoris (L.) Med., Stellaria media (L.) Vill, Chamomilla suaveolens (L.) Pursh Buch. and Viola arvensis Murr. could all be uprooted by less force than it took to uproot carrot. The uprooting angle (0°, 45° and 90°) had no significant influence on the uprooting force for carrot at the studied developmental stage. C. album, S. arvensis, U. urens, Matricaria inodora, Thlaspi arvense L. and carrot could all be uprooted by less than 1 N when they had two true leaves. Carrots required a greater uprooting force than the weeds at the three early developmental stages studied. This indicates that it should be possible to develop selective mechanical weed control methods.     

An agro-economic survey of the weeds and weeding practices in cassava (Manihot esculenta Crantz) in Colombia

A survey of weeds and weeding practices was carried out by a team of agricultural economists and agronomists on 283 farms in five Cassava growing regions of Colombia at three times during a cropping season. Seventy-one to 78% of all weed species present were broadleaved species. As cassava grew older, grass species were present to a greater and sedge species to a lesser relative frequency. Surprisingly Pteridiumaquilinum (L.) Kuhn was the most frequently listed species and Bidens pilosa L. and Cyperus rotundus L. were other frequent problems. Regional variations in the most frequently encountered species were found but several of the weeds were common to many zones. The most frequently encountered species did not usually have the highest plant populations. Most of the annual grasses, sedges and broadleaf weeds found can be controlled by currently recommended herbicides for cassava but further research is needed on Imperata cylindrica (L) Beauv., Melinis minutlftora Beauv., P. aquilinum and Sida spp. The average number of manual weedings was 3.3 per crop, occupying 48 man-days/ha which is 50% of the total labor requirements for cassava production, and more than one-third of the total costs. Reasons for not using herbicides were (1) relative costs of herbicides and labor. (2) lack of information, (3) lack of capital, (4) right herbicides were not available, and (5) herbicides were not available in small packages. This survey has usefully identified new field problems and has suggested further research programs to solve them.     

Effect of weed control treatments on weeds, seed yield, yield components and nodulation in winter lentil

Good weed control is critical in winter lentil production. This study was conducted on the lentil cultivar Sazak 91 during the winter seasons of 1997–98 and 1998–99 to determine the most appropriate method for controlling weeds. Hand weeding (weed‐free control), weedy control (inoculated), weedy control (uninoculated), hand hoeing once, hand hoeing twice, trifluralin, imazethapyr, linuron, prometryn, phenmedipham + desmedipham, trifluralin + hand hoeing and linuron + hand hoeing treatments were evaluated and the effects of herbicides on nodulation in lentil were investigated. In the first year Convolvulus arvensis, Centaurea balsamita, Ranunculus arvensis, Cephalaria syriaca and Lathyrus spp., dominated whereas in the second year Hordeum vulgare, Adonis aestivalis and Centaurea depressa were the dominant weed species in the plots. Prometryn, hand hoeing, linuron and a combination of linuron + hand hoeing were found to be the most effective for control of weeds, resulting in the highest yield in winter lentil throughout the investigation. Trifluralin and imazethapyr had a phytotoxic effect on the lentil plants. None of the weed control treatments had any adverse effects on nodulation and Rhizobium leguminosarum inoculation was not found to have any effect on the competitive ability of the lentil plants.     

Real-time weed detection, decision making and patch spraying in maize, sugarbeet, winter wheat and winter barley

Information on temporal and spatial variation in weed seedling populations within agricultural fields is very important for weed population assessment and management. Most of all, it allows a potential reduction in herbicide use, when post‐emergence herbicides are only applied to field sections with weed infestation levels higher than the economic weed threshold; a review of such work is provided. This paper presents a system for site‐specific weed control in sugarbeet (Beta vulgaris L.), maize (Zea mays L.), winter wheat (Triticum aestivum L.) and winter barley (Hordeum vulgare L.), including online weed detection using digital image analysis, computer‐based decision making and global positioning systems (GPS)‐controlled patch spraying. In a 4‐year study, herbicide use with this map‐based approach was reduced in winter cereals by 60% for herbicides against broad‐leaved weeds and 90% for grass weed herbicides. In sugarbeet and maize, average savings for grass weed herbicides were 78% in maize and 36% in sugarbeet. For herbicides against broad‐leaved weeds, 11% were saved in maize and 41% in sugarbeet.     

The effects of soil texture and moisture on reproductive strategies of Spergula arvensis L. and Plantago major L.

The reproductive strategies of two weeds, Spergula arvensis L. and Plantago major L., were studied in relation to soil texture and moisture regime. On sandy soil, daily watering gave greatest dry wt per plant in S. arivensis, while fortnightly watering gave the greatest in P. major. In P. major, seed production was increased with increased moisture stress in sandy soil, but not in garden soil when watered fortnightly. Conversely, S. arvensis showed a decrease in seed number with increasing moisture stress in both soil types. The reproductive effort of S. arvensis was much greater (26.2–63.1%) than P. major (2.3–9.2%). There was greater emphasis on reproduction by S. arvensis under both soil types and various moisture regimes while P. major was characterized by higher allocation to vegetative structures which may confer a competitive advantage by increasing its efficiency of resource capture. Thus, S. arvensis seems to be r-selected and P. major K-selected. The differences in the reproductive strategies of the two weeds are discussed with reference to the environmental conditions under which they grow in nature.     

Quantifying the detrimental effect of airborne dust on herbicide efficacy

One side effect of human activity and global climatic change is more airborne dust. This not only has undesirable effects on human health and the environment, but may also adversely affect many agricultural processes, including herbicide efficacy. This is particularly relevant in parts of the world where dust storms are common and limited rainfall means dust persists on plants for protracted periods. Accordingly, a series of greenhouse dose–response pot experiments was carried out to quantify the effect of a dust concentration of 1,500 µg/m³ on the performance of paraquat, glyphosate, sulfosulfuron and 2,4-D+MCPA. Dust-treated and untreated seedlings of Hordeum spontaneum and Sinapis arvensis were sprayed with sulfosulfuron and 2,4-D+MCPA, respectively, while paraquat and glyphosate were applied to both weed species. The efficacy of glyphosate and paraquat decreased significantly in the presence of dust on both species. Similar results were observed for 2,4-D+MCPA on S. arvensis. In contrast, the efficacy of sulfosulfuron on H. spontaneum was not affected by dust. In the presence of dust, the doses of glyphosate, paraquat and 2,4-D+MCPA required for a 90% effect were enhanced by a factor of 1.9 to 2.6. The negative impact on glyphosate efficacy was more pronounced in S. arvensis than H. spontaneum, while it was similar for paraquat. Future studies should consider the amount, duration and composition of dust as well as its impact on other weeds and herbicides. Potential approaches to overcome the detrimental influence of dust on the performance of herbicides were also suggested for future studies.     

上海农田主要杂草田间发生消长规律

1972—79年调查研究了上海农田杂草的发生和消长。在野外调查189种农田主要杂草自然发生情况,提出了四个发生型:以藜等为代表的早春发生型;以马唐、稗草等为代表的春、夏发生型;以看麦娘等为代表的秋、冬发生型;以小藜等为代表的春、秋发生型。同时,明确了在不同年份,不同茬口、不同耕作情况下,因环境条件的变化,杂草发生也有差异。掌握它们的发生规律和生长发育特点,为防除杂草及合理、适时应用除草剂提供了一定的理论依据。     

Weight loss in overwintering below‐ground parts of Sonchus arvensis under current and temperature‐elevated climate scenarios in Sweden

Weight loss in overwintering below‐ground parts of perennial weeds has been attributed to respiration, but neither its temperature dependence nor its relevance for biomass dynamics under changing climate conditions have been investigated. In two experiments, we quantified weight loss of the perennial weed Sonchus arvensis, by measuring weight changes over time of sprouting roots in dark rooms at temperatures of 4, 8 and 18°C. Dry weight loss rates were 0.47, 0.64 and 1.47% day^?1 at 4, 8 and 18°C, respectively, giving a half‐life time of 149, 110 and 47 days, respectively. A factor by which weight loss rates increase for every 10° rise in temperature (Q₁₀) was equal to about 2.3. Cumulative weight loss may comprise >40% of the below‐ground biomass during overwintering periods. Applying weight loss rates and Q₁₀ to elevated soil temperature projections showed that losses during winter seasons in central Sweden will remain basically constant, the effect of increased weight loss at higher temperatures being balanced by shorter winters. This implies that need for control of S. arvensis in a changing climate will persist, but that shorter winter seasons will provide a longer time window for control of S. arvensis prior to sowing crops.     

Seed retention of ten common weed species at oat harvest reveals the potential for harvest weed seed control

We assessed the seed production and shedding pattern of 10 common weed species in two oat fields in Denmark. The aim was to evaluate the possibility of harvesting retained seeds on weeds at crop harvest by a combine harvester based on estimation of weed seed retention. Before flowering, ten plants of each weed species were selected and surrounded by a seed trap comprising of a porous net. When the plants started shedding seeds, the seeds were collected from the traps and counted weekly until oat harvest. Just before oat harvest, the retained seeds on the plants were counted and the ratio of harvestable seeds and shed seeds during the growing season was determined. The seed production and shedding patterns varied between the 2 years. Across both years, Anagallis arvensis L., Capsella bursa-pastoris L. Medik, Chenopodium album L., Geranium molle L., Persicaria maculosa Gray, Polygonum aviculare L., Silene noctiflora L., Sonchus arvensis L., Veronica persica Poir. and Viola arvensis Murray retained on average 61.6%, 52.7%, 67.2%, 58.4%, 32.05%, 59.5%, 95.7%, 23.5%, 51.7% and 33.9%, respectively, of their produced seeds at crop harvest. Silene noctiflora was classified as a good target for harvest weed seed control; C. bursa-pastoris, C. album, G. molle, P. maculosa, S. arvensis and V. arvensis were classified as intermediate targets; and A. arvensis, P. aviculare and V. persica were classified as poor targets.     

Control of problem weeds of maize on the Transvaal Highveld (South Africa). II. Datura stramonium L.

As was described in a previous publication, the influence of a number og herbicides and herbicide mixtures which are being used for the post-emergence control of weeds in maize on the Transvaal Highveld, have been tested for their efficiency in the control of problem weeds. Both the percentage mortality and percentage dry mass difference between the test plants and the controls 10 days after application of the respective herbicides were used as bioassay methods. Datura stramonium L. was very susceptible to most of the herbicidal treatments up to the nine-leaf stage. The reason why it is considered a problem weed should perhaps be sought in the erratic germination of its seeds over a number of years, thus evading common practices of weed control.     

Competitive ability and threshold levels of three broadleaf weed species in sunflower

Data collected from field trials carried out in different years and environments were used to determine competitive ability and threshold levels of Ammi majus L., Chenopodium album L. and Sinapis arvensis L. The hyperbolic model showed a good fit to the experimental data. The three broadleaf weeds showed low and similar competitive indices (i ranging from 1–08 to 1–75), supporting the hypothesis of a high sunflower competitive ability. The economic threshold was four to six plants m^?2 for all three weeds in the case of weed control by hoeing and about six plants m^?2 for S. arvensis in the case of a postemergence treatment with imazamethabenz. Limitations and approximations in estimating competitive parameters are pointed out and discussed. Aptitude à la compétition et seuils de nuisibilité de trois mauvaises herbes dicotylédones dans le tournesol Des données recueillies dans des expérimentations au champ conduites dans différents environnements et au cours de différentes années ont été utilisées pour déterminer l'aptitude à la compétition et les seuils de nuisibilité de Ammi majus L., Chenopodium album L. et Sinapis arvensis L. Le modéle hyperbolique fournissait un bon ajustement aux données. Les trois mauvaises herbes avaient des indices de compétition bas et similaires (i de 1,08 à 1,75) ce qui conforte l'hypothèse d'une forte aptitude à la compétition du tournesol. Les seuils économiques étaient 4–6 plantes m^?2 pour toutes les mauvaises herbes dans le cas de désherbage mécanique et environ 6 plantes m^?2 pour S. arvensis dans le cas de traitement de post-levée avec l'imazaméthabenz. Les limitations et les approximations dans l'évaluation des paramètres de la compétition sont identifiés et discutés. Konkurrenzkraft und Schadensschwellen von drei dikotylen Unkrautarten in Sonnenblume Anhand von Ergebnissen aus Freilandversuchen in verschiedenen Jahren auf verschiedenen Standorten wurden die Konkurrenzkraft und die Schadensschwellen von Ammi majus L., Chenopodium album L., und Sinapis arvensis L, bestimmt. Die Ergebnisse ließen sich mit einer hyperbolischen Gleichung gut beschreiben. Die Konkurrenzindices i von 1,08 bis 1,75 waren fur alle 3 Arten ahnlich niedrig, worin sich die starke Konkurrenz der Sonnenblume widerspiegelt. Bei mechanischer Unkrautbekampfung lagen die Schadensschwellen fur alle 3 Unkrauter zwischen 4 und 6 Pflanzen m^?2, fur Nachauflaufbehandlung mit Imazametabenz fur Sinapis arvenis bei 6 Pflanzen m^?2. Grenzen und Annaherung der Bestimmung von Konkurrenzparametern werden eingehend diskutiert.     

Weed Problems and Weed Control in the Commonwealth Caribbean

Abstract

The effect of weeds on crops is discussed, with particular reference to the Commonwealth Caribbean. The most serious weeds in the region are Cyperus rotundas, Cynodon dactylon, Commelina spp., Parthenium hysterophorus, Portulaca oleracea, Cleome spp. and Amaranthus spp. Serious weeds include Eleusine indica, Echinochloa colonum, Euphorbia spp., Brachiaria mutica, Paspalum conjugatum, Sporobolus indicus and Ipomoea tiliaceae. Brief notes are given for these species and also for the locally serious weeds, Rottboellia exaltata, Digitaria sanguinalis, Mimosa pudica, Scleria reflexa, Cenchrus echinatus. Control measures include macheting, hand weeding, flooding, mulching and short-term fallows. Herbicides are used especially by larger vegetable growers and in sugarcane and citrus groves. Paraquat is the most widely used. Other chemicals used in specific situations are listed. Knapsack sprayers are the commonest application method but granular and c.d.a. application is likely to increase. Weed control research in the Commonwealth Caribbean is also briefly reviewed.     

Seed structure and germination in Discaria toumatou (Rhamnaceae)

Data collected from field trials carried out in different years and environments were used to determine competitive ability and threshold levels of Ammi majus L., Chenopodium album L. and Sinapis arvensis L. The hyperbolic model showed a good fit to the experimental data. The three broadleaf weeds showed low and similar competitive indices (i ranging from 1–08 to 1–75), supporting the hypothesis of a high sunflower competitive ability. The economic threshold was four to six plants m^?2 for all three weeds in the case of weed control by hoeing and about six plants m^?2 for S. arvensis in the case of a postemergence treatment with imazamethabenz. Limitations and approximations in estimating competitive parameters are pointed out and discussed. Aptitude à la compétition et seuils de nuisibilité de trois mauvaises herbes dicotylédones dans le tournesol Des données recueillies dans des expérimentations au champ conduites dans différents environnements et au cours de différentes années ont été utilisées pour déterminer l'aptitude à la compétition et les seuils de nuisibilité de Ammi majus L., Chenopodium album L. et Sinapis arvensis L. Le modéle hyperbolique fournissait un bon ajustement aux données. Les trois mauvaises herbes avaient des indices de compétition bas et similaires (i de 1,08 à 1,75) ce qui conforte l'hypothèse d'une forte aptitude à la compétition du tournesol. Les seuils économiques étaient 4–6 plantes m^?2 pour toutes les mauvaises herbes dans le cas de désherbage mécanique et environ 6 plantes m^?2 pour S. arvensis dans le cas de traitement de post-levée avec l'imazaméthabenz. Les limitations et les approximations dans l'évaluation des paramètres de la compétition sont identifiés et discutés. Konkurrenzkraft und Schadensschwellen von drei dikotylen Unkrautarten in Sonnenblume Anhand von Ergebnissen aus Freilandversuchen in verschiedenen Jahren auf verschiedenen Standorten wurden die Konkurrenzkraft und die Schadensschwellen von Ammi majus L., Chenopodium album L., und Sinapis arvensis L, bestimmt. Die Ergebnisse ließen sich mit einer hyperbolischen Gleichung gut beschreiben. Die Konkurrenzindices i von 1,08 bis 1,75 waren fur alle 3 Arten ahnlich niedrig, worin sich die starke Konkurrenz der Sonnenblume widerspiegelt. Bei mechanischer Unkrautbekampfung lagen die Schadensschwellen fur alle 3 Unkrauter zwischen 4 und 6 Pflanzen m^?2, fur Nachauflaufbehandlung mit Imazametabenz fur Sinapis arvenis bei 6 Pflanzen m^?2. Grenzen und Annaherung der Bestimmung von Konkurrenzparametern werden eingehend diskutiert.     

新疆核桃-小麦间作麦田杂草组成及群落特征

为明确新疆核桃与小麦间作对麦田杂草种类及群落结构的影响,于2012—2017年对新疆南疆核桃-小麦间作、单作麦田杂草发生情况进行了调查。结果表明,南疆麦区杂草有39种,隶属14科33属,其中以菊科、禾本科、藜科为主;优势杂草有9种,分别是灰绿藜Chenopodium glaucum L.、稗草Echinochloa crusgalli(L.)Beauv.、播娘蒿Descurainia sophia(L.)Schur.、扁蓄Polygonum aviculare L.、硬草Sclerochloa kengiana L.、田旋花Convolvulus arvensis L.、离蕊芥Malcolmia africana(L.)R. Br.、小蓟Cephalanoplos segetum(Bunge.)Kitam.、苣荬菜Sonchus brachyotus DC.;与小麦单作田相比,核桃-小麦间作麦田杂草物种丰富度及Shannon-Wiener指数较高,2017年物种丰富度最高达27种,代表杂草优势集中性的Simpson指数则是小麦单作田高于核桃-小麦间作麦田,2013年高达0.32;核桃-小麦间作有利于麦田播娘蒿、苣荬菜和离蕊芥发生,但不利于萹蓄发生,其它5种优势杂草在间作和单作麦田的发生密度无显著差异。     

Using geographic information systems to map the prevalent weeds at an early stage of the cotton crop in relation to abiotic factors

Cotton is still one of the most important crops in Greece despite the changes in the country’s socioeconomic status which have reduced the total cultivated area. In order to minimize yield losses, weed control is essential during the cultivation period. The aim of this study was to determine the distribution of the prevalent weeds that escape the usual herbicide application in the main cotton zone, located in the Karditsa prefecture. The weed densities and the irrigation methods used were recorded in 101 sampling sites of 25 m²; the cotton crop had been grown for the last 5 years using similar weed control techniques. Existing soil maps of the area were also used, through which soil data (texture and carbonates content) were accessed. Among the 14 weed species that have been recorded, four were perennial (Cyperus rotundus, Convolvulus arvensis, Cynodon dactylon, Sorhum halepense) and were ranked as first, second, fourth and fifth, respectively, according to the mean density, indicating the inefficient herbicidal control. In the fields irrigated by sprinklers, the weeds occurred in greater populations than those that occurred in fields irrigated by drippers, at values of 4.64 and 3 weeds m^-2, respectively. In terms of the studied soil properties, the distribution of C. arvensis was significantly correlated with carbonate content and soil texture in the surface soil layer. The autocorrelation analysis showed that only perennial weeds are spatially correlated whereas the interpolated maps showed this spatial trend of weed appearance.     

The Royal Show

Abstract

A non-mechanical system of applying herbicides to weeds taller than crops by a simple rope wick device is described. The herbicide applicator requires no pumps or moving parts to deliver the herbicide, and it can be built by the farmer at a very low cost. Selective control of johnsongrass (Sorghum halepense (L.) Pers.) in soyabeans (Glycine max (L.) Merr.) with glyphosate was demonstrated in two experiments under field conditions.     

喷雾助剂对茎叶处理除草剂的增效机制及应用研究进展

农田草害的发生严重影响了农业生产和发展,使用除草剂进行化学防治是目前最省时省力和防除效果最好的除草方法.其中,茎叶处理除草剂因其具有不受土壤环境影响、按草施药、灵活和选择性高等优点,应用范围更广.然而,茎叶处理除草剂在喷雾施药过程中由于受到杂草叶片界面特性的影响,常出现药液迸溅、滚落、难以渗透等现象,导致除草剂用量增大...