Susceptibility of seven annual grasses to herbicides

The relative susceptibility of Digitaria sanguinalis (L.) Scop, (large crabgrass), Echinochloa crus-galli (L.) Beauv. (barn-yardgrass), Eriochloa villosa (Thumb.) Kunth. (hairy cup-grass), Setaria faberi Herrm. (giant foxtail), Setaria lutescens (Weigel) Hubb. (yellow foxtail), Setaria viridis (L.) Beauv. (green foxtail) and Setaria viridis var. robusta-purpurea Schreiber (robust-purple foxtail) to alachlor, atrazine, butylate and cyanazine was studied under glasshouse conditions. Hairy cupgrass was the least susceptible to the herbicides tested, of which alachlor appeared to be the most effective. Large crabgrass was controlled by alachlor, butylate and cyanazine at all of the rates tested, but by atrazine only at rates above 0–56 kg/ha. All four herbicides provided acceptable control for barnyardgrass, giant foxtail, green foxtail, robust-purple foxtail, and yellow foxtail. The susceptibility of the grasses to cyanazine and alachlor was correlated with seed size. Alachlor was more effective in controlling green foxtail and hairy cupgrass when applied to the soil surface before emergence than when incorporated into the soil prior to sowing. Sensibility de sept graminées annuelles à divers herbicides La sensibilité relative des espéces suivantes: Eriochloa villosa (Thumb,) Kunth. Echinochloa crus-galli (L.) Beauv. (panic). Digitaria sanguinalis (L.) Scop, (digitaire), Setaria faberi Herrm, (sétaire). Setaria viridis (L.) Beauv., Seiaria viridis var. robusla-purpurea Schreiber ct Seiaria lutescens (Weigel) Hubb., (sétaires) a étéétudiéé en serre. vis-d-vis de I'atrazine. de la cyanazine, du butylate et de I'alachlore. Eriochloa villosa a été I'espéce la moins sensible aux herbicides essayds parmi lesquels I'alachlore s'est montré le plus efficace. La digitaire a été maitrisé par I'alachlore, le butylate et la cyanazine k toutes les doses essayees, mais pour I'atra-zine. seulement à des doses supérieures à 0.56 kg/ha. Ces quater herbicides ont donne des resultats acceptables contre le panic, et les sétaires (S. faberi, S. viridis, S. viridis var. robusta-purpurea, S. lutescens). La sensibilité des graminées à la cyanazine et à I'alachlore fut en corrélation avec la taille des semences. L'alachtore s'est montré plus efficace contre la sétaire S. viridis var. robusta-purpurea ct contre l'Eriochloa villosa quand il a été appliqué sur la surface du sol avant la levée que lorsqu'il a éié incorporé au sol avant le semis. Die Empfindlichkeit von sieben einjährigen Gräsern gegenüber Herbiziden. Es wurde die relative Empfindlichkeit von Digitaria sanguinalis (L.) Scop., Echinochloa erus-galli (L.) Beauv., Eriochloa villosa (Thumb.) Kunth-, Setaria faberi Herrm., Setaria lutescens (Weigel) Hubb., Setaria viridis (L.) Beauv. und Setaria viridis var. robusta-purpurea Schreiber gegenuber Atrazin, Cyanazin, Butylat und Alachlor unter Gewächs-hausbedingungen untersucht. Eriochloa him war gegenúber den gepruften Herbiziden am wenigsten empfindlich, Alachlor scliien die beste Wirkung zu haben. Digiiaria sanguinalis wurde durch Alachkir. Butylat und Cyanazin bei alien gepruften Aiifwandmengen bekampft, durch Atrazin aber nur bei Aufwandmengen ilber 0.56 kg/ha. Alte vier Herbizide ergaben eine brauchbare Bekampfung von Echinochloa crus-galli, Seiaria Jabcri, Seiaria viridis. Setaria viridis var. robusta-purpurea und Setaria luiescens. Die Emptindlichkeit der Gräser gegenüber Cyanazin und Alachlor stand in Beziehung zur Samengrösse. Alachlor bekämpfte Seiaria viridis und Erioehloa villosa im Vor-auflaufverfahren besser als im Vorsaatverfahren mit Ein-arbeitung.     

Control of barnyardgrass and yellow foxtail by herbicides in relation to the sucrose content of the seedling leaves

The ability of triazine and urea herbicides to reduce the sucrose level of seedlings of barnyardgrass (Echinoehloa crusgalli (L.) (Beauv.) and yellow foxtail (Setaria Iutescens (L.) Beauv.) was compared with their effectiveness in controlling these weeds by pre-emergence application to maize. In 2 years out of 3 a significant positive correlation was obtained between the sucrose content of the third leaf and the number of these grasses on the field plots 2 months after planting. The regression of number of grasses on sucrose content for the combined treatments of 3 years was also significant indicating that, in general, control of grasses is improved as the inhibition of photosynthesis in the seedlings is increased.     

Use of wild Setaria viridis (L.) Beauv. to improve triazine resistance in cultivated S. italica (L.) by hybridization

Interspecific hybrids were obtained between two triazine-resistant forms of the wild species Setaria viridis and the triazine-susceptible cultivated foxtail millet (Setaria italica). The main agronomic characteristics of the hybrids were generally intermediate between the parental forms, except for fertility which was low. Some differences were observed according to the wild parent used. Progeny analysis confirmed the cytoplasmic inheritance of the resistance. The creation of resistant cultivars would allow the use of triazines in foxtail millet cultivation.     

Asulam mixtures for weed control in flax

Five field experiments were conducted from 1972 to 1975 to evaluate weed control in flax (Linum usitatissimum L.) using post-emergence treatments of asulam [methyl (4-aminobenzenesulphonyl) carbamatel alone and in combination with other herbicides. The ¹⁴C-asulam absorption by leaf segments and roots of glasshouse grown wild oats (Avena fatua L.) was also investigated. Asulam at 1.12 kg/ha gave good wild oat control and acceptable control of green foxtail (Setaria viridis (L.) Beauv.). However, wild oat control was poorer when asulam was combined with other herbicides: on a 3-year average, as compared with asulam alone at equal rates, the asulam+MCPA mixture resulted in a greater antagonism and a significant 6% reduction in flax seed yield, whereas the asulam+bromoxynil/MCPA mixture gave the least antagonistic effect, improved broadleaf weed control and increased yield by 13%. In mixtures, the potassium salt of MCPA was more compatible with asulam for weed control than the amine form. Both leaf segments and roots of wild oats absorbed and distributed less ¹⁴C-asulam from solutions containing MCPA than from those containing bromoxynil or bromoxynil/MCPA.     

Agronomic performance of a triazine resistant foxtail millet (Setaria italica (L.) Beauv.)

The agronomic performance of a foxtail millet line resistant to atrazine, obtained through interspecific hybridization between Setaria viridis and S. italica, was compared to that of the original susceptible cultivar of S. italica. In spite of lower grain yields when both were grown in identical conditions, the use of this resistant material is justified because its yield when weeded with atrazine was similar to that of the susceptible cultivar with handweeding. There were no differences in early season growth rates between these lines at cool temperatures.     

An aspartate to glycine change in the carboxyl transferase domain of acetyl CoA carboxylase and non‐target‐site mechanism(s) confer resistance to ACCase inhibitor herbicides in a Lolium multiflorum population

BACKGROUND: The increasing use of ACCase‐inhibiting herbicides has resulted in evolved resistance in key grass weeds infesting cereal cropping systems worldwide. Here, a thorough and systematic approach is proposed to elucidate the basis of resistance to three ACCase herbicides in a Lolium multiflorum Lam. (Italian rye grass) population from the United Kingdom (UK24). RESULTS: Resistance to sethoxydim and pinoxaden was always associated with a dominant D2078G (Alopecurus myosuroides Huds. equivalent) target‐site mutation in UK24. Conversely, whole‐plant herbicide assays on predetermined ACCase genotypes showed very high levels of resistance to diclofop‐methyl for all three wild DD2078 and mutant DG2078 and GG2078 ACCase genotypes from the mixed resistant population UK24. This indicates the presence of other diclofop‐methyl‐specific resistance mechanism(s) yet to be determined in this population. The D2078G mutation could be detected using an unambiguous DNA‐based dCAPS procedure that proved very transferable to A. myosuroides, Avena fatua L., Setaria viridis (L.) Beauv. and Phalaris minor Retz. CONCLUSION: This study provides further understanding of the molecular basis of resistance to ACCase inhibitor herbicides in a Lolium population and a widely applicable PCR‐based method for monitoring the D2078G target‐site resistance mutation in five major grass weed species. Copyright © 2010 Society of Chemical Industry     

粟杆蝇(ATHERIGONA BISETA KARL)的研究

粟杆蝇幼虫为害谷子常造成枯心或不实。此虫一年发生二代,部分一代。以老熟幼虫在5—10厘米土层中越冬。成虫于6月中旬出現,6月末达盛期,每雌产11—41卵,产卵于粟杆的基部。粟杆蝇的发生为害与湿度有密切关系,交尾、产卵、幼虫孵化、以及侵入粟茎均需高湿。田間枯心率与当年6月份降雨量的相关系数为0.71(P<0.01),相关显著。在晚播、高肥、密植的条件下,枯心发生严重。谷子品种、生育速度均与被害程度有关。在粟田雌蝇出現高峯期噴5％DDT与0.5％666等量混合粉剂,有良好的防治效果。     

粟白发病抗病性研究Ⅱ我国粟白发病菌生理小种及其分布

 1988~1993年在北京用采自中国4个谷子生态区白发病菌[Sclerospora graminicola(Sacc.) Schröt.]标样,以新创造的单病株(系)卵孢子菌土种子包衣接种法研究了我国粟白发病菌的生理小种。结果显示,白发病菌株与粟品种间有强互作反应,说明粟白发病菌的致病力有特异性。经选择,确定三三二、西城白、大青苗、柳条青和189等5个品种为一套适宜于测试粟白发病菌生理小种的鉴别品种。根据68个参试菌株在5个鉴别品种上的反应特征,初步将我国白发病菌区分为6群20个生理小种,并明确了各小种在各生态区的分布,我国4个谷子生态区中,黄土高原病菌小种类群最多,致病力也较强。     

A single polymerase chain reaction-based assay for simultaneous detection of two mutations conferring resistance to tubulin-binding herbicides in Setaria viridis

A simple method based upon polymerase chain reaction (PCR) was developed to detect mutant alleles of the gene encoding α2-tubulin, which confers recessive resistance to tubulin-binding herbicides in Setaria viridis. Multiplex, bidirectional allele-specific PCR (Mbi-PASA) was shown to specifically and reliably detect the presence of all sensitive (Leu₁₃₆, Thr₂₃₉) and resistant (Phe₁₃₆, Ile₂₃₉) α2-tubulin alleles in a single reaction. Double-blind analysis of 2000 S. viridis seedlings using seed bioassay and Mbi-PASA confirmed that the presence of two mutant α2-tubulin alleles in a seedling was always associated with cross-resistance to dinitroaniline and benzoic acid herbicides, sensitivity to a benzamide herbicide, and hypersensitivity to carbamate herbicides. No other resistance mechanism was detected in the S. viridis populations screened. Successful Mbi-PASA genotyping was achieved with fresh and dried plant fragments from the field. Compared with bioassays, Mbi-PASA is faster and more robust, removing the need for live plant material. It is the only way of detecting recessive resistance before resistant plants occur in a field. Mbi-PASA can be performed with basic molecular biology laboratory equipment, and is suitable for high-throughput genotyping adaptation. It is the tool of choice for resistance diagnosis in such cases where only a few recessive, target-derived, genes control resistance to herbicides.     

小米红叶病的研究Ⅰ.红叶病,小米的一个新的病毒病害

 最近六年来,在我国的主要小米产区,包括山东、河北、河南和山西四省均报道有小米植株变红的现象,农民称它为红叶病或红丝病。     

EFFECT OF CHLORTHAL DIMETHYL ON OAT AND FOXTAIL SEEDLING ANATOMY*

Summary. The root and shoot growth of oat (Avena sativa L.) and green foxtail (Setaria viridis (L.) Beauv.) were generally reduced proportionately to the concentration of chlorthal dimethyl applied. Foxtail shoot growth was stimulated by a concentration of 2 ppm. Cells in the shoot and root meristems of treated plants were completely disarranged and considerably hypertrophied. Differentiation was irregular and extended nearer the apices in tissue of treated seedlings than in normal tissue. Histochemical tests showed that the amount of starch, proteins and nucleic acids in seedling tissue decreased with an increase of chlorthal dimethyl concentration, whereas the endosperm of the seeds retained more starch and protein than the controls. The walls of shoot nieristem and root epidermal cells were thickened or altered so as to stain more intensely than corresponding cells in untreated tissue. Effet du diméthyle chlorthal sur l'anatomie des plantules d'avoine et de séaire     

Characterisation of target-site resistance to ACCase-inhibiting herbicides in the weed Alopecurus myosuroides (black-grass)

Resistance to aryloxyphenoxypropionate (AOPP), cyclohexanedione (CHD) and phenylurea herbicides was determined in UK populations of Alopecurus myosuroides Huds. Two populations (Oxford AA1, Notts. A1) were highly resistant (Resistance indices 13-->1000) to the AOPP and CHD herbicides fenoxaprop, diclofop, fluazifop-P and sethoxydim, but only marginally resistant to the phenylurea, chlorotoluron. Analyses of acetyl coenzyme A carboxylase (ACCase) activity showed that an insensitive ACCase conferred resistance to all the AOPP/CHD herbicides investigated. Another population, Oxford S1, showed no resistance to sethoxydim at the population level, but contained a small proportion of plants (<10%) with an insensitive ACCase. Genetic studies on the Notts A1 and Oxford S1 populations demonstrated that target site resistance conferred by an insensitive ACCase is monogenic, nuclearly inherited with the resistant allele showing complete dominance. Investigations of the molecular basis of resistance in the Notts A1 population showed that sethoxydim resistance in A myosuroides was associated with the substitution of an isoleucine in susceptible with a leucine in resistant plants, which has also been found in three other resistant grass-weed species (Setaria viridis (L) Beauv, Avena fatua L, Lolium rigidum Gaud).     

Taxonomic characterization of Pyricularia isolates from green foxtail and giant foxtail, wild foxtails in Japan

Twenty-eight Pyricularia isolates from two wild foxtails—green foxtail (Setaria viridis) and giant foxtail (S. faberii)—in Japan were taxonomically characterized by DNA analyses, mating tests, and pathogenicity assays. Although most of the isolates failed to produce perithecia in mating tests with Magnaporthe oryzae, a diagnostic polymerase chain reaction-restriction fragment length polymorphism phenotype of M. oryzae was detected in the beta-tubulin genomic region in all isolates. The pathogenicity assays revealed that host ranges of the isolates were similar to those of isolates from foxtail millet (S. italica), which were exclusively pathogenic on foxtail millet. In addition to the 28 isolates from wild foxtails, 22 Pyricularia isolates from 11 other grasses were analyzed by RFLP using single-copy sequences as probes. In a dendrogram constructed from the RFLP data, isolates that were previously identified as M. oryzae formed a single cluster. All the wild foxtail isolates formed a subcluster with foxtail millet isolates within the M. oryzae cluster. From these results, we conclude that Pyricularia isolates from the wild foxtails are closely related to isolates from foxtail millet and should be classified into the Setaria pathotype of M. oryzae.     

Prediction of weed seedling densities from buried seed reserves

Bioeconomic models for weed management ultimately require knowledge of weed densities. Weed seedling populations may be predicted by multiplying emergence rates by seedbank densities. However, emergence rates vary according to species, year and management. Furthermore, seedbank estimates may vary with sampling technique, size, number and date. These variables must be quantified before bioeconomic models can be used profitably. Consequently, two experiments were initiated, both in conventionally managed maize. The first experiment documented proportional seedling emergence across years and sites for three taxa: foxtail (Setaria glauca [L.] Beauv. and S. viridis [L.] Beauv. combined), pigweed (Amaranthus retroflexus L.), and lambsquarters (Chenopodium album L.). The second experiment was devoted to methodology for estimation of seedbanks: sampling date (autumn or spring), technique (seed extraction or glasshouse germination), and soil sample size for the seed extraction technique. For emergence rates, the following order was observed: foxtail > lambs-quarters > pigweed. Emergence rates for each species were related in a parabolic manner to growing degree-days in April. The glasshouse technique appeared to be more reliable than seed extraction for correlation with field seedling densities. For the seed extraction technique, a minimum soil sample size of 100 g was necessary. A spring sampling date appears to be more reliable than an autumn date, probably because many seemingly viable seeds die during winter. Prevision de la densité deplantules d'adventices a partir des reserves de graines enfouies Les modèles bioéconomiques en matière de desherbage impliquent la connaissance des densités d'adventices. Les populations de plantules adventices peuvent être prévues à partir des taux de levées multipliés par les densités du stock grainier. Cependant, les taux de levée varient avec les espèces, l'année, et les méthodes culturales; et les estimations du stock grainier peuvent varier avec la technique d'échantillonnage, son nombre, sa taille et sa date. Ces variables doivent être quantifiées avant que les modèles bioéconomiques puissent être utilisés avec profit. En conséquence, deux expérimentations ont été mises en place, les deux en culture de maïs conventionnelle. La première expérimentation a indiqué le taux de levée des plantules pour les différentes années et sites de 3 taxons: setaires (Setaria glauca [L.] Beauv. et S. viridis [L.] Beauv., en association), amaranthe réfléchie (Amaranthus retroflexus L.) et chenopode blanc (Chenopodium album L.). La seconde expérimentation était consacrée à la méthodologie d'estimation du stock grainier: date d'échantillonnage (automne ou printemps); technique (extraction des graines ou germination en serre) et taille de l'échantillon de sol pour la technique df'extraction des graines. Pour les taux de levée: sétaires > chénopode blanc > amaranthe. Les taux de levée pour chaque espèce sont liés de façon parabolique avec les degrés/jour de croissance en Avril — la technique en serre apparaît plus fiable que l'extraction des graines pour la corrélation avec les densités d'adventices au champ. Pour la technique d'extraction des graines, la taille minimum de l'échantillon nécessaire était de 100 g: un échantillonnage de printemps apparait meilleur qu'un d'automne, probablement parce que de nombreuses semences paraissant viables meurent durant l'hiver. Prognose der Keimpflanzendichte von Unkräutern nach dem Samenvorrat im Boden Bioökomische Modelle in der Unkrautbekämpfung setzen die Kenntnis der Unkrautdichte voraus. Die Keimpflanzendichte kann mit dem Produkt aus der Samendichte im Boden mit der Keimrate errechnet werden. Die Keimrate variiert jedoch je nach Pflanzenart, Jahr und Kulturbedingungen, und die Bestimmung der Samenbank hängt von der Probennahmetechnik, -größe, -zahl und -zeit ab. Diese Variablen müssen quantifiziert werden, um brauchbare bioökonomische Modelle zu erhalten. Deshalb wurden in normal angebautem Mais 2 Versuche angelegt, um zum einen die Keimpflanzendichte von 3 Arten(gruppen), Fuchsrote Borstenhirse (Setaria glauca (L.) Beauv.)+Grüne B. (S. viridis (L.) Beauv.), Zurückgekrümmter Amarant (Amaranthus retroflexus L.) und Weißer Gänsefuß (Chenopodium album L.), über die Jahre und an verschiedenen Punkten festzustellen und sich zum anderen mit der Methodik der Bestimmung der Samenbank zu befassen: Probennahmezeit (Herbst und Frühjahr), -technik (Samenauswaschung oder Keimung im Gewächshaus) und Bodenprobenumfang. Die Keimraten (im April) waren: Borstenhirse > Gänsefuß > Amarant. Die Keimung im Gewächshaus ergab für die Korrelation mit der Keimpflanzendichte im Feld bessere Werte als die Samenauswaschung. Für die Auswaschung waren mindestens 100 g Boden erforderlich. Probennahmen im Frühjahr erwiesen sich als günstiger als im Herbst, vermutlich wegen des Absterbens vieler keimfähiger Samen über Winter.     

4种药剂防治压砂西瓜田一年生杂草田间药效试验

采用田间小区试验方法进行4种药剂防除压砂西瓜田杂草田间药效试验.结果表明：50％敌草胺乳油1125 g a.i./hm2、72％异丙甲草胺乳油756 g a.i./hm2可有效防除压砂西瓜田的小画眉草、地锦草、狗尾草、小藜、虎尾草等.     

Evaluation and QTL mapping of resistance to powdery mildew in lettuce

Lettuce (Lactuca sativa) is the major leafy vegetable that is susceptible to powdery mildew disease under greenhouse and field conditions. Quantitative trait loci (QTLs) for resistance to powdery mildew under greenhouse conditions were mapped in an interspecific population derived from a cross between susceptible L. sativa cultivar Salinas and the highly susceptible L. serriola accession UC96US23. Four significant QTLs were detected on linkage groups LG 1 (pm‐1.1), LG 2 (pm‐2.1 and pm‐2.2) and LG 7 (pm‐7.1), each explaining between 35 to 42% of the phenotypic variation. The four QTLs are not located in the documented hotspots of lettuce resistance genes. Alleles for the disease resistance at the four QTLs originated from both parents (two from each), demonstrating that even highly susceptible accessions may provide alleles for resistance to powdery mildew. These QTLs appeared to operate during limited periods of time. Results of the field trials with F_2:3 and F_3:4 families derived from a Soraya (moderately resistant) × Salinas cross demonstrated effective transfer of resistance to powdery mildew in this material. An integrated rating approach was used to estimate relative levels of resistance in 80 cultivars and accessions tested in a total of 23 field and greenhouse experiments. Generally, very low resistance was observed in crisphead‐type lettuces, while the highest relative resistance was recorded in leaf and butterhead types. Comparison of two disease assessment methods (percentage rating and the area under the disease progress steps, AUDPS) for detection of QTLs shows that the two approaches complement each other.     

Note: Proline — An inducer of resistance against pearl millet downy mildew disease caused by<Emphasis Type="Italic">Sclerospora graminicola</Emphasis>

In an attempt to find a suitable alternative to the otherwise perilous chemical control strategy of disease management, the amino acid proline was evaluated for its efficiency to elicit resistance in pearl millet (Pennisetum glaucum (L.) R. Br.) against downy mildew disease caused bySclerospora graminicola (Sacc.) Schroet both under greenhouse and field conditions. Proline treatment to seeds at 50 mM concentration for 3 h, significantly enhanced the seed germination and seedling vigor of pearl millet in comparison with the control. The same concentration and duration of seed treatment protected the pearl millet plants from downy mildew by offering 58% protection under greenhouse and 67% protection under field conditions. Studies revealed that 3 days were required for proline-treated plants to develop resistance, which was systemic and was sustained throughout the life of the plants. Apart from disease protection, proline was also found effective in enhancing vegetative and reproductive growth of the plants, as evidenced by the increase in height, fresh weight, leaf area, tillering capacity, 1000-seed weight and grain yield in comparison with the control plants. http://www.phytoparasitica.org posting Oct. 3, 2004.     

Herbicide‐resistant weeds in the Philippines: Status and resistance mechanisms

Two major weeds in rice in the Philippines, Sphenochlea zeylanica Gaertn. and Echinochloa crus‐galli (L.) Beauv., are controlled with chemical and cultural methods. In the 1980s, after >10 years of continuous use of 2,4‐D, S. zeylanica evolved resistance to the chemical in those rice fields that had been treated with 2,4‐D once or twice every cropping season. In the 1990s, E. crus‐galli evolved resistance to butachlor and propanil in rice monocrop areas where both herbicides were used continuously for 7–9 years. Rice farmers continue to use 2,4‐D, butachlor and propanil extensively and are often unaware of herbicide resistance or the potential for cross‐resistance, its causes or its implications. In order to control herbicide‐resistant E. crus‐galli, farmers are shifting to locally available herbicides with different modes of action, such as bispyribac, an acetolactate synthase inhibitor, and cyhalofop, an acetyl coenzyme A carboxylase inhibitor. Follow‐up manual weeding or rotary weeding after herbicide spraying, a common farmers’ practice, removes the susceptible and resistant biotypes and could help to delay or prevent the evolution of resistance. Although the resistance mechanisms of both weeds are not determined yet, they could be related to enhanced degradation that is similar to the mechanisms that are shown by the resistant biotypes in other countries.     

Absence of 3-(2,4-dichlorophenoxy)propionic acid in plants treated with 2,4-dichlorophenoxyacetic acid‡

Experiments were conducted to establish if the formation of 2.4-dichlorophenol (DCP) from 2.4-dichlorophenoxyacetic acid (2,4-D) in plants proceeds via 3-(2,4-dichtorophenoxy) propionic acid (2,4-DP) as an intermediate. Soybean (Glycine max (L.) Merr.), kidney bean (Phaseolus vtitgaris L.), pea (Pisum. sativum L.), smooth bromegrass (Bromus inermis Leyss.), wild oat (Avena fatua L.), yellow foxtail (Setaria glauca(L.) Beauv.), barley (Hordeum vulgare L.), timothy (Phleum pratense L.). and orchardgrass (Dactylis glomerata L.) were treated with equal weights of 2,4-D and 2,4-DP. After 3 days, all plants contained DCP; however, amounts were larger in plants treated with 2.4-DP than in those treated with 2,4-D. The 2.4-DP was absorbed from the leaf surface more efficiently than 2,4-D. No evidence was found for formation of 2,4-DP from 2,4-D in any of the plant species studied. L'absence de l'acide3-(2,4 dichlorophénoxy) propionique dans les plantes traitées avec I'acide 2,4-dichlorophénoxyacétique Des experiences ont été effectuées pour rechercher si la formation de 2,4-dichlorophénoI (DCP) dans les plantes, à partir de l'acide 2.4-dichlorophénoxy acétique (2,4-D) se produit par l'intermêdiaire de l'acide 3-(2,4-dichlorophenoxy) propionique. Le soja (Glycine max(L.) Merr.). le haricot (Phaseolus vuigaris L.), Ic pois (Pisum sativum L.), le brome (Bromus inermis Leyss.), la folle avoine (Avena fatua L.), la sétaire (Setaria glauca(L.) Beauv.). I'orge (Hordeum vulgare L.), la fléole (Phleum pratense L.) et le dactyle (Dactylis ghmerata L.) ont été traités par des poids égaux de 2.4-D et de 2,4-DP. Trois jours aprés, les plantes contenaient du DCP; toutefois, les quantités trouviés furent plus importantes dans les plantes traitées avec le 2,4-DP que dans celles traitées avec le 2,4-D. Le 2,4-DP a été absorbéà partir de la surface foliaire plus efficacement que le 2,4-D. La formation du 2,4-DP à partir du 2,4-D n'a pu être prouvée dans aucune des plantes étudiécs. Die Abwesenheit von 3-(2,4′Dichlorphenaxy)-propionsäure irt mil 2,4-Dichlorphenoxytesäure behandelten Pflanzen Es wurden Versuche durchgeführt um herauszufinden. ob die Bildung von 2,4-Dichlorphenol (DCP) aus 2.4-Dichlor-phenoxyessigsäure (2,4-D) in Pflanzen über 3-(2,4-Dichlor-phenoxy)-propionsaure (2,4-DP) als Zwischcnprodukt ver-läufl. Sojabohnen (Glycine max(L.) Merr.), Gartenbohnen (Phaseolus vutgaris L.), Erbsen (Pisum sativum L.), Wehrlose Trcspe (Bromus inermis Leyss.), Flughafer (Avena fama L.), Gelbe Borsienhirse (Setaria glauca(L.) Beauv.), Gerste (Hordetim vidgarc L.), Wiesenlieschgras (Phleum pratense L.) und Knaulgras (Dactylis ghmerata L.) wurden mit gleichen Mengen an 2,4-D und 2,4-DP behandelt. Nach drei Tagen enthielten alle PHanzen DCP; aber die Menge an DCP war in den mit 2,4-DP behandelten Pflanzen grosser als in den mit 2,4-D behandelten. 2,4-DP wurde von der Blatt-oberflache besser absorbiert als 2.4-D. In keiner der untersuchten Pflanzenarten konnte ein Hinweis für die Bildung von 2,4-DP aus 2,4-D gefunden werden.     

Chemical control of herbicide-resistant Lolium rigidum Gaud. in north-eastern Spain

BACKGROUND: Lolium rigidum Gaud. is one of the most common weed species in winter cereals in north‐eastern Spain, with populations that have evolved resistance to herbicides becoming more widespread since the mid‐1990s. Nine trials on commercial fields with herbicide‐resistant L. rigidum were conducted during the cropping seasons 2001–2002 to 2003–2004, testing the efficacy of 20 herbicides and mixtures pre‐ and post‐emergence and as sequential applications. Weed populations chosen had different resistance patterns to chlortoluron, chlorsulfuron, diclofop‐methyl and tralkoxydim, representative of the resistance problems faced by farmers. RESULTS: In pre‐emergence, prosulfocarb mixed with trifluralin, chlortoluron or triasulfuron was effective on six populations. In post‐emergence, iodosulfuron alone or mixed with mesosulfuron gave the best results but did not control three resistant populations. At Ferran 1, none of the herbicide combinations reached 90% efficacy. CONCLUSIONS: The diverse efficacy patterns of the different populations demonstrate the need for detailed knowledge of the populations before using herbicides. Moreover, the unexpected insufficient efficacy of the new herbicide iodosulfuron prior to its field use shows the need to combine herbicides with other non‐chemical weed control methods to control resistant L. rigidum in north‐eastern Spain. Copyright © 2010 Society of Chemical Industry