Photosynthetic parameters in glyphosate-treated sugarbeet (Beta vulgaris L.)

Variable fluorescence and carbon dioxide exchange rate (CER) were measured in intact leaves of glyphosate-treated sugarbeet plants, to investigate rapid effects on photosynthesis. In one experiment, a significant effect on variable fluorescence and CER was found within 8 h after herbicide application. The effect on stomatal conductance was not significant. In a second experiment, the effects of light or dark conditions during herbicide application and 24 h later were evaluated. Under light conditions glyphosate significantly reduced variable fluorescence after 4 h. However under initial conditions of 24 h darkness, followed by alternating 8 h light/8 h dark, the effect was not significant until 44 h after treatment, by which time the plants had received several hours of light. The eflect on variable fluorescence 8 h after herbidde application correlated positively with plant survival 7 days later.     

Weed control in groundnut (Arachis hypogaea L.) with polyethylene film mulching

Studies conducted during the winters of 1997 - 98 and 1998 - 99 (December - March) at the Regional Research Station, Tamil Nadu Agricultural University, Vridhachalam, India, revealed the usefulness of polyethylene film mulching in arresting weed growth and maximizing pod yield in groundnut. Among the various treatments, two (1) crop grown under polyethylene film mulching and (2) pre-planting incorporation of fluchloralin in the flat-bed system of sowing registered the lowest weed numbers at harvest (106.7 and 113.7/plot of 27 m 2 in 1997 - 98 and 1998 - 99 respectively), the lowest weed dry-matter production (51.2 and 54.5 g/plot of 27 m 2 ), maximum weed control efficiency (62.1 and 57.4%) and weed control index (83.0 and 81.1%), the highest number of matured pods/plant (17.6 and 18.0), 100 kernel weight (48.6 and 48.7 g), percentage shelling (72.6 and 72.8) and a dry pod yield of 2451 and 2468 kg ha -1 when compared with non-mulched plots. The net return and benefit:cost ratio was also highest with the same treatment in both the study periods.     

Weed control and selectivity in maize (Zea mays L.) with tembotrione mixtures

Field and pot trials were conducted in two sites of northern Greece (Thermi and Lepti) to study selectivity and weed control in maize (Zea mays L.) with herbicide mixtures based on tembotrione. Treatments included tembotrione (plus isoxadifen-ethyl safener) applied alone at 100 g ai/ha and three mixtures of tembotrione with: (i) rimsulfuron at 10 g ai/ha, (ii) nicosulfuron at 40 g ai/ha and (iii) foramsulfuron at 60 g ai/ha (label rates for weed control in maize). Herbicides were applied at the 7- to 8-leaf growth stage of maize in Thermi and at the 6- to 7-leaf growth stage in Lepti. Six weeks after treatment, control of rhizomatous Sorghum halepense with tembotrione alone was 63% in Thermi and 60% in Lepti, with plants showing the typical bleaching symptoms of the HPPD-inhibiting herbicides. Control of rhizomatous S. halepense with the mixtures was improved from 63% to 86% in Thermi and from 60% to 82% in Lepti compared with the single treatment of tembotrione, with plants showing only the symptoms of reddish/purplish color of the ALS-inhibiting herbicides. Control of common broadleaf weeds of maize, such as Xanthium strumarium, Amaranthus retroflexus, Datura stramonium, and Chenopodium album was excellent (92%–100%) either with tembotrione alone or with the mixtures, with plants showing the typical bleaching symptoms of the HPPD-inhibiting herbicides. None of the mixtures affected the ear length and grain yield of maize. All chemical treatments gave higher grain yield than that of the non-treated control and comparable yield to that of the weed-free control. Grass control (Echinochloa crus-galli, E. phyllopogon, and Setaria viridis) with tembotrione alone was above 90% in the pot experiments which was similar to that achieved with the mixtures. Overall, there was an adequate margin of safety in the use of tembotrione in mixture with ALS-inhibiting herbicides for improved weed control in maize, particularly where rhizomatous S. halepense is problematic.     

Use of electricity to control bolters in sugar beet (Beta vulgaris L.): a comparison of the electrothermal with chemical and mechanical cutting methods

A machine was built to kill reproductive plants (‘bolters’) in sugar beet by high-voltage electricity. A generating system producing 10, 13 or 17 kV each at 54 kW was connected to a set of guarded electrodes spanning twelve rows, suspended 5–15 cm above the top of a sugar-beet crop. With 13 kV the system travelling at 5 km h^?1 could clear a light-to-moderate infestation of bolters at a rate of 2·4 ha h^?1 with the tractor's diesel-fuel consumption at 3·51 ha^?1. In 1979, the electrothermal machine, used twice, reduced viable seed returns by 83%; the flail mower used once or twice by 44 and 76–84%; the wire reel mower used once or twice by 45 and 80–87%; and the roller chemical applicator used once by only 13%. Further trials were made in 1981 with an improved electrothermal machine, a rope wick applicator and a flail mower when all gave over 90% control of viable seeds. The electrothermal machine killed between 38 and 41% of bolters compared with 65% for the chemical applicator. The flail mower did not kill any plants. Although possessing many advantages, the electrothermal machines are heavy and more expensive than alternative methods. Development has ceased in the U.K. on electrical weed control but one company in the U.S.A. is selling such equipment.     

Weed competition in irrigated cotton (Gossypium barbadense L.) and groundnut (Arachis hypogaea L.) in the Sudan Gezira

Losses of crop yield due to weed competition in unweeded plots averaged nearly 60% of weed-free yields in cotton and 70% in groundnuts. Weed competition was not directly related to weed groundcover but was dependent on the seasonal growing conditions. The critical period of weed competition in both crops was the 6 weeks between 4 and 10 weeks after crop emergence. During this period cotton could tolerate up to 25% weed groundcover without appreciable loss in crop yield. Groundnuts could tolerate not more than 10% weed cover before yield loss occurred. A main factor in achieving standards of weed control within these limits was preventing the early growth of monocotyledonous weed species: pre-sowing application of trifluralin and benfiuralin provided this over a wide range of growing conditions.     

Inter- and intraspecific competition of fat-hen (Chenopodium album L.) and groundsel (Senecio vulgaris L.)

The responses of Chenopodium album L. and Senecio vulgaris L. to inter- and intra-specific competition were investigated in both additive and replacement series experiments under glasshouse conditions. When grown with tomato the two weed species had similar effects on shoot dry weight at low densities but 5. vulgaris showed more competitive effect at higher densities. Weed density did not affect the concentrations of N, P, K, Ca or Mg in tomato shoots but dry matter and total amounts of nutrients were reduced increasingly with the increase in density of both weeds. The concentration of nutrients in the shoots of the weeds was not affected by density but dry matter yield and total nutrient accumulation per plant fell as the density increased. The concentrations of N, P, K and Mg in the shoots were higher in C. album than S. vulgaris but that of Ca was lower. In a replacement series experiment the two weed species behaved differently. With C. album, both dry matter yield and total nutrient per plant were reduced as its proportion in the mixture increased but, with S. vulgaris, dry matter per plant increased with its proportion in the mixture. One plant of C. album grown with five S. vulgaris gave a higher shoot dry weight than when present in higher proportions or in a pure stand. In a pure stand of six plants the shoot dry weight per plant of C. album was 26% of that of one plant grown with five S. vulgaris. In comparison, the shoot dry weight of one S. vulgaris in pure stand was 120% of that of one plant grown with five C. album. The reduction in growth of C. album was associated with a greater reduction in its ability to accumulate K than other elements. The competition index (CI) of C. album in terms of dry weight decreased with its proportion in the mixture but the reverse was true for S. vulgaris. The relative competitive ability index (RCAI) of C. album was almost 3–5 times that of S. vulgaris. The results showed that differences between the weeds in inter- and intraspecific competition were closely related to the growth of their root systems. Compétition inter- et intraspécifique du chénopode (Chenopodium album L.) et du senecon (Senecio vulgaris L.) Les réponses du chénopode (Chenopodium album L.) et du sénecon (Senecio vulgaris L.) à la compétition inter- et intra-spécifique ont étéétudiées en serre lors d'expériences à séries additives ainsi qu'à séries de remplacement. Quand elles étaient cultivées avec des tomates, les deux mauvaises herbes avaient des effets similaires sur la matière sèche des parties aériennes à faibles densités, mais S. vulgaris se montrait plus compétitif à fortes densités. La densité des mauvaises herbes n'affectait pas les concentrations en N, P, K, Ca et Mg dans les parties aériennes de la to-mate. Par contre, la matière séche et les quantités totales de nutriments étaient d'autant plus réduites que la densité des deux mauvaises herbes était élevée. La concentration en nutriments dans les parties aeriennes des mauvaises herbes n'était pas affectée par leur densité mais le rendement en matière sèche et l'accumulation totale de nutriments par plante décroissaient lorsque la densité augmentait. Les concentrations en N, P, K et Mg dans les parties aériennes étaient plus élevées chez C. album que chez S. vulgaris mais celle de Ca était plus basse. Dans une expérience à séries de remplacement, les deux espèces de mauvaises herbes se comportaient différemment. Chez C. album, le rendement en matière sèche ainsi que la quantité totale de nutriments par plante diminuaient lorsque sa proportion dans le mélange augmentait mais, chez S. vulgaris, la matière sèche par plante augmentait avec sa proportion dans le mélange. Un pied de C. album cultivé avec 5 pieds de S. vulgaris produisait davantage de matière sèche aérienne que lorsqu'il était présent en proportions plus importantes ou en culture pure. Dans une culture pure de 6 plantes, la matière sèche aérienne par pied de C. album représentait 26% de celle d'une plante cultivée avec 5 pieds de S. vulgaris. En comparaison, la matière sèche aérienne par pied de S. vulgaris en culture pure représentait 120% de celle d'une plante cultivée avec 5 pieds de C. album. La réduction de croissance de C. albumétait associée à une réduction de sa capacitéà accumuler K, qui était plus marquée que pour les autres éléments. L'Indice de Compétition de C. album en terme de matière sèche diminuait avec sa proportion dans le mélange, mais l'inverse était vrai pour S. vulgaris. L'Indice Relatif d'Aptitude à la Compétion de C albumétait presque 3,5 fois plus élevé que celui de S. vulgaris. Les résultats montraient que les différences entre les mauvaises herbes en ce qui concerne la compétition inter- et intra-spécifique étaient étroitement liées à la croissance de leur système racinaire. Inter- und intraspezifische Konkurrenz des Weißen Gänsefußes (Chenopodium album L.) und des Gemeinen Greiskrauls (Senecio vulgaris L.) Die inter- und intraspezifische Konkurrenz von Chenopodium album und Senecio vulgaris wurde sowohl in additivem als auch substitutivem Versuchsansatz im Gewächshaus untersucht. In Mischbeständen mit Tomate hatten beide Unkrautarten bei geringer Pflanzendichte eine ähnliche Wirkung auf die Sproß-Trockenmasse, doch Senecio vulgaris war bei hohen Dichten konkurrenzstärker. Die Unkrautdichte hatte keinen Einfluß auf den N-, P-, K-, Ca- oder Mg-Gehalt der Tomatensprosse, aber die Trockenmasse und der gesamte Nährstoffgehalt nahm mit zunehmender Dichte der beiden Unkräuter ab. Der Nährstoffgehalt in den Sprossen der Unkräuter wurde durch die Pflanzendichte nicht beeinflußt, aber die Trockenmasse und der gesamte Nährstoffgehalt nahm mit zunehmender Dichte der beiden Unkräuter ab. Der N-, P-, K-und Mg-Gehalt war bei Chenopodium album höher als bei Senecio vulgaris, doch der Ca-Gehalt war niedriger. In einem substitutiven Versuchsansatz verhielten sich die beiden Unkrautarten verschieden. Bei Chenopodium album wurden sowohl die Trockenmasse als auch der gesamte Nährstoffgehalt pro Pflanze im selben Maße reduziert, wie sein Verhältnis im Mischbestand zunahm; bei Senecio vulgaris stieg die Trockenmasse pro Pflanze mit seinem Anteil im Mischbestand an. Chenopodium album entwickelte bei einem Mischungsverhältnis von l Pflanze zu 5 Senecio-vulgaris-Pflanzen eine höhere Sproß-Trockenmasse als bei höheren Verhältnissen oder im Reinbestand. In einem Reinbestand von 6 Pflanzen war bei Chenopodium album die Sproß-Trockenmasse pro Pflanze 26 % der Masse einer Pflanze, die mit 5 Senecio-vulgaris-Pflanzen wuchs. Bei Senecio vulgaris dagegen war die Sproß-Trockenmasse pro Pflanze im Reinbestand 120 % der Masse einer Pflanze, die mit 5 Chenopodium-album-Pflanzen wuchs. Mit der Wuchshemmung ging bei Chenopodium album eine Abnahme seiner Fähigkeit, K und andere Nährstoffe aufzunehmen, einher. Der Konkurrenzindex von Chenopodium album, bezogen auf die Trocken-masse, nahm mit seinem Anteil in den Mischbeständen ab, während bei Senecio vulgaris das Gegenteil der Fall war. Die relative Konkurrenzfähigkeit von Chenopodium album war fast 3.5mal so groß wie die von Senecio vulgaris. Die Unterschiede der inter- und intraspezifischen Konkurrenz der beiden Unkrautarten stand in enger Beziehung zur Entwicklung ihres Wurzelsystems.     

Herbicides for control of broomrape (Orobanche ramosa L.) in tobacco (Nicotiana tabacum L.)

In field tests conducted on oriental and flue-cured tobacco, six herbicides were evaluated for their effect on broomrape (Orobanche ramosa L.) control and on tobacco growth, yield and chemical composition. Imazaquin+pendi-methalin (1:6) at 0.09+0.55 kg a.i. ha^?1 soil in corporated before transplanting controlled broomrape effectively only in 1990 and signifi cantly reduced tobacco yield. Glyphosate (as Roundup 360 ga.e.1^?1 and Armada (90 ga.e.l^?1) and sulfosate, each at 0.2+0.3 kg a.e. ha^?1 and imazaquinat 0.07+0.1 kg a.i. ha^?1 foliar applied at 40 days and 60 days after transplanting gave excellent control of broomrape, with no adverse effect on tobacco growth or yield; however, the 9% formulation of glyphosate was damaging. Maleic hydrazide gave moderate to good (up to 80%) control of broomrape. Reducing sugars in flue-cured tobacco and nicotine in both oriental and flue-cured tobacco were higher where a her bicide was used. Des herbicides pour lutter contre Orobanche ramosa L. dans le tabac (Nicotiana tabacum L). Dans des expérimentations au champ conduites sur du tabac oriental et ‘flue cured’, six herbicides ont étéévalués pour leur effet sur Orobanche ramosa L. ainsi que sur la croissance, le rendement et la composition chimique du tabac. Le mélange imazaquin+pendiméthalin (1:6 à 0.09+0.55 kg ha^?1, incorporé avant le repiquage, n'a permis de détruire l'orobanche qu'en 1990 et réduisait de manière significative le rendement du tabac. Le glyphosate (Roundup, 360 m.a. 1^?1 et Armada, 90 g m.a. l^?1) et le sulfosate chacun aux doses 0.2+0.3 kg m.a. ha^?1 et l'imazaquin 0.07+0.1 kg m.a. ha^?1 appliqués en post-levée 40 et 60 jours après le repiquage donnaient d'excellents résultats contre l'orobanche, sans effet sur la croissance du tabac et sur son rendement, si l'on excepte la formulation de giyphosate 9%. L'hydrazide maléique donnait des résultats moyens à bons (jusqu'à 80% d'efficacité). Les teneurs en sucres réducteurs chez le tabac ‘flue cured’ et en nicotine chez les tabacs ‘flue cured’ et oriental étaient plus élevées lorsqu'un herbicide avait été utilisé. Herbizide zur Bekämpfung von Orobanche ramosa L. in Tabak (Nicotiana tabacum L.) In Freilandversuchen wurden in Orient- und Vir-gin-Tabak 6 Herbizide hinsichtlich der Bekämpfung der Sommerwurz Orobanche ramosa sowie des Wachstums, des Ertrags und der chemischen Zusammensetzung des Tabaks geprüft. Mit einer Mischung von Imazaquin mit Pendimethalin zu 0,09+0,55 kg AS ha^?1, vor dem Pflanzen in den Boden eingearbeitet, konnte die Sommerwurz nur 1990 wirkungsvoll bekämpft werden, aber der Tabakertrag wurde signifikant reduziert. Glyphosat (als Roundup [360 g AS 1^?1] und als Armada [90 g AS 1^?1) mit Sulfosat zu 0,2+0,3 kg AS ha^?1 und Imazaquin zu 0,07 sowie 0,1 kg AS ha^?1, 40 bzw. 60 Tage nach dem Pflanzen angewandt, wirkten hervorragend, ohne Wuchs und Ertrag des Tabaks zu beeinträchtigen, ausgenommen bei der 9% igen Glyphosatformulierung. Mit Maleinhydazid ließ sich die Sommerwurz befriedigend bis gut (bis zu 80 %) bekämpfen. Der Gehalt an reduzierenden Zuckern im Virgin-Tabak und Nikotin in beiden Tabaken war erhöht, wenn ein Herbizid angewandt worden war.     

A third cryptic virus in beet (Beta vulgaris)

Japanese leaf beet Beta vulgaris var. cicla cv. Fudanso plants were found to contain four double-stranded RNA (dsRNA) components in apparently healthy beet plants. Two were identified as from beet cryptic virus 1 (BCV1), but the other two showed different mobilities on gel electrophoresis and were transcribed into complementary DNA (cDNA) and cloned. Hybridization analysis showed no significant sequence homology between these two dsRNAs and the dsRNA components of BCV1 or the other known cryptic virus of beet, BCV2. Slot- and dot-blot hybridization were used with cDNA clones as probes to identify plants containing these two dsRNA components. Virus particles were purified from these plants and were shown to contain the two new dsRNA components, thus demonstrating the existence of a new beet cryptic virus, which we have called BCV3.     

Responses of otebo bean (Phaseolus vulgaris L.) to postemergence herbicides

Ontario otebo bean growers have few herbicide options available for weed management. Six field trials were conducted in Ontario, Canada, over a 2 year period (2003 and 2004) to evaluate the tolerance of otebo bean to the postemergence (POST) application of bentazon at 1080 and 2160 g ai ha⁻¹, fomesafen at 240 and 480 g ai ha⁻¹, sethoxydim at 500 and 1000 g ai ha⁻¹, quizalofop-p-ethyl at 72 and 144 g ai ha⁻¹, imazamox plus fomesafen at 25 + 200 and 50 + 400 g ai ha⁻¹, and imazamox plus bentazon at 25 + 600 and 50 + 1200 g ai ha⁻¹. All treatments, including the untreated control, were maintained weed-free during the growing season. The POST application of bentazon, imazamox plus fomesafen, and imazamox plus bentazon caused as much as 9% visual injury and reduced the plant height ≤ 12%, reduced the shoot dry weight ≤ 32%, and delayed maturity but had no adverse effect on the yield of otebo bean. Fomesafen, sethoxydim, and quizalofop-p-ethyl applied POST caused as much as 8% visual injury but this was transient and had no adverse effect on the plant height, shoot dry weight, seed moisture content, and yield of otebo bean, except for quizalofop-p-ethyl, which reduced the shoot dry weight as much as 18%. Based on these results, bentazon, fomesafen, sethoxydim, quizalofop-p-ethyl, imazamox plus fomesafen, and imazamox plus bentazon applied POST have an adequate margin of crop safety for weed management in otebo bean production in Ontario. However, care must be taken to avoid spray overlaps to prevent injury from bentazon, imazamox plus fomesafen, and imazamox plus bentazon.     

Pre-sowing herbicides in irrigated cotton (Gossypium barbadense L.) and ground nut (Arachis hypogaea L.) in the Sudan. I. Weed control and crop yields achieved with trifluralin and benfluralin.

Trifluralin in cotton and benfluralin in groudnut. incorporated pre-planting. gave satisfactory control of grass weeds and increased crop yields substantially. Oxadiazon as a pre-planting treatment did not give satisfactory additional control of dicotyledons resistant to the first two herbicides. A post-sowing mechanical ridging operation controlled some herbicide resistant weeds, but its effects depended on timing, weed species and growing conditions. Supportive hand weeding of resistant weeds (mainly dicotyledons) was most effective 4 weeks after crop emergence. Crop yields similar to clean weeded controls were achieved by combining trifluralin or benfluralin with moderate supportive hand weeding and re-ridging. Herbicide applications could be made several months before crop planting during the dry season, giving more effective use of spray equipment and operatives. Delays of up to 24 hours between spraying and incorporation by normal cultivation could be tolerated without loss of herbicidal activity.     

Competition between Silene vulgaris (Moench) Garcke and alfalfa (Medicago sativa L.)

Growth indices describing the nature of the competitive relationship between Silene vulgaris and alfalfa during crop establishment were determined from experiments conducted outdoors in southem Manitoba in 1986 and 1987. The results of the experiments indicated that alfalfa dry matter yields were influenced more by intra- than interspecific competition. In comparison S. vulgaris was affected more by interspecific competition. Replacement diagrams and aggressivity indices both demonstrated that alfalfa and S. vulgaris were the aggressor and sub-ordinate species, respectively. Relative replacement rates for alfalfa versus S. vulgaris were significantly greater than unity, indicating that alfalfa exerted a greater replacement pressure on S. vulgaris than did S. vulgaris on alfalfa. Over time alfalfa could be expected to replace S. vulgaris as the dominant species within a population. Barley was more competitive than alfalfa with S. vulgaris. Not only was S. vulgaris shoot dry weight reduced more by barley than by alfalfa during the establishment year, but fewer S. vulgaris seedlings emerged the following year in plots that had been seeded to barley than in those that had been seeded to alfalfa.     

7种除草剂对红麻田杂草的防除效果和安全性

通过对7种不同除草剂防除红麻福红991田杂草的筛选试验,结果表明,敌草胺、乙草胺、精异丙草胺等7种除草剂对红麻田杂草株防效和鲜重防效差异均不显著,对杂草株防效达到78%~98%,对杂草鲜重防效达到77%~98%。48%氟乐灵EC对福红991的安全性最好,福红991植株鲜重达到3.35 kg/m2。     

Weed control in rose-scented geranium (Pelargonium spp)

Abstract: Field investigations were carried out during 1999 and 2000 to identify effective chemical/ cultural methods of weed control in rose-scented geranium (Pelargonium spp). The treatments comprised pre-emergence applications of oxyfluorfen (0.15, 0.20 and 0.25 kg AI ha(-1)) and pendimethalin (0.50, 0.75 and 1.00kg AI ha(-1)), successive hand weeding, hoeing and mulching using spent of lemon grass (at 5 tonnes ha(-1)) 45 days after planting (DAP), three hand-weedings 30, 60 and 90 DAP, weed-free (frequent manual weeding) and weedy control. Broad-leaf weeds were more predominant than grass and sedge weeds, accounting for 85.8% weed density and 93.0% weed dry weight in 1999 and 77.2% weed density and 93.9% weed dry weight in 2000. Unrestricted weed growth significantly reduced geranium oil yield, by 61.6% and 70.6% in 1999 and 2000, respectively. Pre-emergence application of pendimethalin (0.75-1.00 kgAI ha(-1)) or oxyfluorfen (0.25 kg AI ha(-1)), successive hand-weeding, hoeing and mulching and three hand-weedings were highly effective in reducing weed density and dry weight and gave oil yield comparable to the weed-free check. Application of oxyfluorfen (0.15 or 0.20 kg AI ha(-1)) and pendimethalin (0.50 kg AI ha(-1)) were less effective in controlling the weed species in geranium. None of the herbicides impaired the quality of rose-scented geranium oil measured in terms of citronellol and geraniol content.     

Chemical and cultural control of bulrush (Scirpus maritimus L.) and annual weeds in lowland rice (Oryza sativa L.)

Chemical and non-chemical or cultural approaches for the control of Scirpus maritimus L. (bulrush) and of annual weeds in lowland rice were examined in the field. Herbicides such as bentazon [3-isopropyl-1H-H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] and 2,4-D [2,4-dichlorophenoxy)acetic acid] effectively controlled S. maritimus but not the annual grasses [Echinochloa glabrescens Munro ex Hook. f. and Echinochloa crus-galli ssp. hispidula [(Retz.) Honda] when applied at the six- to eight-leaf stage 20–28 days after transplanting or seeding rice). S. maritimus was not adequately controlled when the herbicides were applied pre- or early post-emergence. A granular formulation of bensulfuron-methyl [(methy1–2-[[(4,6-dimethoxypirimidin-2-yl)aminosulfonylmethyl]benzoate)] applied 6 or 8 days after transplanting or seeding (two- to four-leaf stage of the weed) effectively controlled S. maritimus and the annuals E. glabrescens, E. crus-galli ssp. hispidula, and Monochoria vaginalis, Presl. (Burm. f.) S. maritimus stand was drastically reduced by shifting land preparation back and forth from wet to dry. Neither tillage intensity nor use of intermediate-statured modern rice cultivars affected the weed stand. La lutte chimique et culturelle contre le scirpe (Scirpus maritimus L.) et les mauvaises herbes annuelles en culture de riz (Oryza sativa L.) Des possibilitiés chimiques et culturelles dans la lutte contre Scirpus maritimus L. (le scirpe) et les mauvaises herbes annuelles en culture de riz ont fait l'objet d'une étude sur le terrain. Appliqués au stade 6- à 8-feuilles des graminées annuelles, Echinochloa glabrescens Munro ex Hook. f. et Echinochloa crus-galli ssp. hispidula [(Retz) Honda] (20 à 28 jours après le repiquage ou le semis du riz), les herbicides, tel le bentazone [isopropyl-3 1H 3H-benzothiadazine-2,1,3 one-4 dioxyde-2,2] et le 2,4-D [acide 2,4-dichlorophénoxyacétique] ont permis une lutte efficace contre S. maritimus mais pas contre les graminées. La maîtrise de S. maritimusétait insuffisante quand les traitements herbicides ont été appliqués en prélevée ou en postlevée précoce. Une forme granulée de bensulfuron-methyl, appliquée 6 ou 8 jours après le repiquage ou le semis (stade deux- à quatre-feuilles de l'adventice) a permis une lutte efficace contre S. maritimus ainsi que les adventices annuelles E. glabrescens, E. crus-galli ssp. hispidula et Monochoria vaginalis (Burm. f.) Presl. Une réduction dramatique dans le peuplement de S. maritimus a suivi l'emploi alterné de techniques humides el sèches dans la préparation du sol. Ni l'intensité du labourage ni l'emploi de variétés de riz modernes de hauteur moyenne n'ont eu d'influence sur l'enherbement. Bekämpfung der Strand-Simse (Scirpus maritimus L.) und einjähriger Unkräuter in Nass-Reis (Oryza saliva L.) mit chemischen und Kulturmethoden Mit Herbiziden wie Bentazon und 2,4-D konnte Scirpus maritimus, nicht aber die einjährigen Gräser Echinochloa glabrescens Munro ex Hook, und Echinochloa crus-galli ssp. hispidula (Retz.) Honda bekämpft werden, wenn sie im 6- bis 8-Blatl-Stadium (20 bis 28 Tage nach dem Pflanzen oder der Saat des Reises) behandelt wurde. Die Bekämpfung war aber unzureichend, wenn die Herbizide vor oder kurz nach der Keimung ausgebracht wurden. Mit bensulfuron-methyl Granutat 6 oder 8 Tage nach dem Pflanzen oder der Saat (2- bis 4-Blatt-Stadium der Unkräuter) konnten Scirpus maritimus und Echinochloa glabrescens sowie E. crus-galli ssp. hispidula und Monochoria raginalis (Burm. f.) Presl. Bekämpft werden. Die Verschiebung der Bodenbearbeitung von nass nach troeken verringerte die Verunkrautung mit Scirpus maritimus erheblieh. Der Unkrautbestand wurde weder durch verschiedene Intensität der Bodenbearbeitung noch durch die neuen mittellangen Reissorten herabgesetzt.     

Weed control with pre-sowing herbicides in irrigated cotton (Gossypium barbadense L.) and groundnut (Arachis hypogaea L.) in the Sudan. II. Economic, labour requirement, crop safety and operational aspects of trifluralin and benfluralin

Soil incorporated. pre-sowing application of trifiuralin in cotton or of benfluralin in gruundnut, each at 1–68 kg a.i., ha, cut labour requirement for handweeding to levels where the tenant could he largely independent of hired labour, Economic returns from a combination of these herbicides plus supportive hand- weeding for herbicide-resistant species compared favourably with those from hand- weeding only as presently recommended. Application and incorporation of trifluralin and benfluralin fited well into existing practices for seedbed preparation and any likely modifications of these. There was no evidence of crop phytoxicity and crop maturity was not affected. Residue analysis indicated no soil residue problems for crops in rotations and no residues were detected in crop seed. Trifluralin applied many months in advance of cotton planting in the dry season, did not start to disappear until the soils were wetted just before couon planting.     

Agronomic practises for weed control in turmeric (Curcuma longa L.)

Weeds are the main problem with turmeric (Curcuma longa L.) cultivation where herbicides are not allowed. This is because herbicides cause water contamination, air pollution, soil microorganism hazards, health hazards, and food risks. Considering turmeric's medicinal value and the environmental problems caused by herbicides, various agronomic practises have been evaluated for non‐chemical weed control in turmeric. One additional weeding is required before turmeric emergence and weed infestation is much higher when turmeric is planted in February and March, as compared to April, May or June planting. A similarly higher yield of turmeric is achieved when it is planted in February, March, and April, compared to late plantings. Weed emergence and interference are not affected by planting depth, seed size, planting pattern, planting space, ridge spacing, and the row number of turmeric until 60 days after planting. This is because turmeric cannot develop a canopy structure until then. Thereafter, weed infestation reduces similarly and significantly when turmeric is planted at depths of 8, 12, and 16 cm, compared to shallower depths. The yield of turmeric at these depths is statistically the same, but the yield for the 16 cm depth is difficult to harvest and it tends to decrease. Turmeric grown from seed rhizomes (daughter rhizomes) weighing 30–40 g reduces weed infestation significantly and obtains a significantly higher yield compared to smaller seeds. The mother rhizome also can suppress weed infestation and increase the yield markedly. Around 9% weed control and 11% higher yield are achieved by planting turmeric in a triangular pattern compared to a quadrate pattern. The lowest weed infestation is found in turmeric grown in a 20 or 30 cm triangular pattern and the highest yield is obtained with the 30 cm triangular pattern. Turmeric gown on two‐row ridges spaced 75 cm apart shows excellent weed control efficiency and obtains the highest yield. This review concludes that turmeric seed rhizomes of 30–40 g and/or the mother rhizome could be planted in a 30 cm triangular pattern at the depth of 8–12 cm on two‐row ridges spaced 75–100 cm apart during March to April in order to reduce weed interference and obtain a higher yield. Mulching also suppresses weed growth and improves the yield. The above agronomic practises could not control weeds completely; biological weed management practises could be integrated in turmeric fields using rabbits, goats, sheep, ducks, cover crops or intercrops.     

牧草盲蝽在南疆的发生危害及其防治

牧草盲蝽在南疆一年发生4代 ,以6月中下旬～7月初第 2代若虫和成虫的危害对棉花产量威胁最大 ,常造成棉株中下部蕾铃大量脱落。防治该虫以农业防治和机械网捕法效果较好。