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Assessment of herbicide resistant crops in reference to Germany’s Reduction Program in Chemical Plant Protection – Analysis of an 8-year experiment with glufosinate resistant oilseed rape and maize
Summary
The complete article is written in German
Results of a long-term experiment with glufosinate resistant oilseed-rape and maize were analysed regarding their importance for reduction of intensity and ecotoxicological risks of herbicide use. For this purpose, the treatment indices (BI) and SYNOPS risk potentials for biological risk were calculated. The BI in herbicide resistant maize increased in comparison with the conventional variant (1.2 vs. 0.9). In herbicide resistant oilseed rape, the BI was below the conventional variant right from the start (0.9 vs. 1.3). In both herbicide crops, SYNOPS risk potentials for aquatic organisms were reduced. In conclusion, herbicide resistant oilseed rape and maize in linkage with early or late post-emergence uses of glufosinate could be a future option that can meet main goals of Germany’s Reduction Program in Chemical Plant Protection.
Field trails on weed control in genetically modified glufosinate resistant sugar beet under ploughing and reduced tillage conditions
Summary
The complete article is written in German
In a field experiment from 1995 to 2001, options of weed control in genetically modified, glufosinate resistant (Liberty Link®) sugar beets have been evaluated. These sugar beets were cultivated under conventional (PF) and conservative tillage methods (MU). The field trail show that by using herbicide resistant sugar beets; it was possible to reduce the frequency of treatments with herbicides as well as the amount of herbicide used.
In the years 1996, 1997, 1999 and 2001 the field trials were destroyed by unknown persons. Despite that fact, it was possible to come to statements concerning the use of the herbicide resistant technology (HR Technology). Through the opportunity of a later herbicide use the integrated weed control in the sugar beet cultivation can be developed further. The control of weeds requires a very early herbicide application, since the authorized products only achieve a satisfying efficacy, if the weeds are still in the cotyledonous and first leaf stages. Therefore, under current practical conditions, a consequent and integrated weed management based on threshold levels cannot be realised. This concept applies weed control only in critical periods of sugar beet growth.
The experiment showed that the effect of Liberty 18 SL (Glufosinate 183g/l) on important arable weeds allows a later application. This could be the basis for further enhancements of weed control systems in the sugar beet cultivation and enables the sugar beet grower to conduct a more targeted weed control. Weeds mostly affect sugar beets at a later stage of development.
Through the cultivation of genetically modified, herbicide resistant sugar beets, it was possible to reduce the frequency of herbicide applications as far as to one application. The application of the soil sparing conservative cultivation method in sugar beet cultivation can be facilitated by the use of the HR-Technology. Thus, it could be possible to reduce pre-emergence treatments with herbicides.
Furthermore, the trials showed that a more flexible weed management is possible through the combination of herbicide resistant sugar beets with the herbicide Liberty 18 SL. That enables the sugar beet grower to conduct the herbicide application at a time. Thereby, soil structure damages can be minimized and consequently, the sustainability of modern agricultural cropping systems can be improved.
Experiences of introduction of imidazolinone-resistant sunflower in Hungary from the herbological point of view
Summary
Sunflower growing area reached about 450,000-500,000 hectares in Hungary in the last few years. A weak point of weed control of sunflower is the application of herbicides mainly against Ambrosia artemisiifolia (Common ragweed) and Cirsium arvense. As Hungarian soils are highly infected with these weeds, there is a need to find more reliable and effective solutions on weed control of sunflower.
Clearfield-Technology on sunflower was introduced in the spring of 2005 in Hungary on about 40.000 hectares mainly with the hybrid Rimisol. The application of this new weed control technology was observed with high expectations from the practice.
Studies were carried out in July 2005 in North-West-Hungary on some sunflower fields and the efficiency of the IMI-technology has been evaluated.
We established that early post application of Pulsar 40 SL (imazamox) that gives new possibilities for the control of dangerous weeds in sunflower, but there are some more details that should be further tested e.g. the use of pre-emergence weed control before Pulsar application. Based on our studies we also concluded that application of imazamox gives high efficacy for the control of non-planted conventional sunflower (from previous crop, as weed) on IMI-sunflower fields.
Assessment of transgene spread from oilseed rape by population dynamic and molecular analyses of feral oilseed rape
Summary
The complete article is written in German
Oilseed rape ( Brassica napus L.) has a certain potential to persist not only in arable fields but also in seminatural habitats and is therefore often found on ruderal sites, along road verges and railroad tracks. In view of the future cultivation of genetically modified oilseed rape in Germany and of the possible spread of transgenes our objective was to investigate the origin and the persistence of feral oilseed rape plants. To this end, oilseed rape plants detected at 74 ruderal locations between 2001 and 2004 were characterized in a comparative way through molecular ISSR markers and biochemical seed content analysis. In addition, population dynamic parameters like seed production and seed germination were determined in order to estimate the reproduction potential of ruderal oilseed rape. The results of our survey show that chances for the formation of permanent ruderal populations are very low despite the high reproduction potential of feral oilseed rape on ruderal sites. Germination, seedling development and the formation of viable seeds are highly dependent on the type of soil surface, on competing vegetation, on the occurrence of herbivores and pathogens as well as on management measures.
Avoiding herbicide resistance in weeds and conserving the active ingredients – A challenge for field advice, research and practice considering as example black-grass ( Alopecurus myosuroides Huds.)
Summary
The complete article is written in German
Reports about efficacy of graminicides against black-grass ( Alopecurus myosuroides Huds.) and other monocotyledonous species are increasing throughout different regions of Germany. If mistakes in herbicide application can be excluded the weed populations are probably complete or partly resistant. Herbicides belonging to inhibitors of PSII, ACCase and ALS are mostly affected. An important reason for this development is the continuous or nearly continuous use of herbicides with the same mode of action (MoA). This is promoted by agricultural factors which are responsible for the increasing density of grass species in fields. A rational herbicide management is necessary to preserve the herbicides where resistance exists against one ore more mode of action. Where no resistance occurred until today strategies to prevent the spread of resistance are necessary. The use of herbicides and agriculture measures are complementary. Different mode of action has to be combined and alternate. This needs a broad enlightenment of the practitioner. Besides the advice institutions, the research and the industry must deliver their dues.
Regional study of herbicide resistance of Alopecurus myosuroides Huds. in France
Summary
Since the 1990s in the north-west of Europe, the spread of herbicide resistance in wheat weeds such as Alopecurus myosuroides Huds. (blackgrass) is becoming more and more important. In the French administrative district Côte d’Or resistance to fenoxaprop within A. myosuroides populations was first detected in 1996. In 2003, 149 fields from this district were randomly sampled and about 125 A. myosuroides populations were tested for herbicide resistance. The agronomic history of all sites was investigated. Most the populations of A. myosuroides investigated contained at least 50 % of plants with resistance to fenoxaprop. In 53 and 9 % of these populations at least 50 % of plants were resistant to flupyrsulfuron and to clodinafop, respectively. Only one population could be considered as resistant to isoproturon. Strategies for A. myosuroides control are discussed in the light of this work. Herbicide resistance of A. myosuroides in the district Côte d’Or was mapped using GIS and the software Arcview®.
Management of metabolic resistant black-grass ( Alopecurus myosuroides Huds.) populations in Germany – challenges and opportunities
Summary
In the intensive winter-wheat growing areas, characterized by winter crop mono-culture, no ploughing, early seeding times and heavy soils, typical for the coastal and river marshlands in Lower Saxony and Schleswig-Holstein, black-grass populations were selected over several years, which exhibit resistance against several herbicides from different mode of action classes. A monitoring program was conducted over years, and confirmed in 2004 again the results from 2001-2003 that practically all resistant populations had developed a metabolic resistance mechanism. On 2 locations an additional ACCase-target-site resistance was found. A mathematical model developed for metabolic resistance demonstrates that such black-grass populations can not be controlled in a sustainable manner by only relying on herbicides. A successful long-term strategy includes a combination of agronomic measures, in particular ploughing, and herbicide programs. Mixtures of different herbicides are usually more effective than sequences in programs. Herbicide programs should aim for optimum control in the fall. Lexus® (flupyrsulfuron-m) + a residual herbicide, applied early post-em fall, consistently showed high levels of control. The pre-treatment with flupyrsulfuron-m has a positive effect on the activity against black-grass of a subsequently applied ALS-inhibitor herbicide.
Ecology of silky bent grass ( Apera spica-venti (L.) Beauv.), its importance and control in the Czech Republic
Summary
Silky bent grass is a common weed in winter cereals with an increasing occurrence in the Czech Republic in recent years. Field observations and laboratory experiments were carried out to extend the knowledge of its ecology in relation to further spread and control. The research was focussed on the following areas: i.) distribution in various geographical and natural conditions, ii.) influence of farming practices on its occurrence, iii.) differences in dormancy and germination in local populations, and iv.) control measures and their efficacy. Silky bent grass occurs regularly in 80 % of all observed localities and increasing harmfulness was declared by 31.6 % of the inquired farmers. Silky bent grass occurs strongly in the west and central part of the Czech Republic. The map of distribution was created. Factors partially stimulating its occurrence were altitude and N-fertilization; soil tillage was not a significant factor. Ureas (isoproturon, chlortoluron) and sulfonylureas (chlorsulfuron, iodosulfuron, sulfosulfuron), which create together 80 % of the total usage of herbicides are the most and long-term used herbicides against silky bent grass. Five populations with suspected resistance to chlorsulfuron were found. The seeds germinated well after maturation, but during afterripening the germination increased linearly to mid October (60 %). No differences in germination were found between the resistant and sensitive populations during afterripening. The seeds from the soil depth of 1 mm emerged best, followed by the seeds on the soil surface.
On herbicide resistance within Apera spica-venti (L.) P.B.
Summary
The complete article is written in German
Ninety seed samples of Apera spica-venti with IPU dominated field treatments in the past demonstrated resistance against isoproturon in 21 cases. One population from North Rhine-Westphalia seems to be unsusceptible also against iodosulfuron, propoxycarbazone and fenoxaprop, but susceptible against sulfosulfuron. The progeny of individuals which were not killed by fenoxaprop were cross resistant against clodinafop, cycloxydim and sethoxidim, but not against clethodim. The resistance level of this selected population against fenoxaprop could be enhanced by a progressive selection pressure within 4 generations with the result of tolerating now 80times the recommended field rate. The selection model employed here allows an easy prognosis of the resistance dynamics of vulnerable grass weeds within a relatively short time even for active ingredients not used before.
First case of resistance to sulfonylurea herbicides reported in Switzerland: a biotype of loose silky-bent ( Apera spica-venti (L.) Beauv.)
Summary
The first case of resistance to sulfonylurea herbicides reported in Switzerland is described in this paper. It concerns a biotype of loose silky-bent (Apera spica-venti L.), one of the most serious weedy grass infesting arable fields in Switzerland. The exact level and amplitude of this resistance, as well as its mechanism and genetics still need to be specified; but preliminary results demonstrate unambiguously its existence. Today, it is justified to strictly implement the rules aiming at avoiding further development of this resistance in fields; first of all a rotational use of herbicides with different modes of action.
During the last decade, ALS-inhibiting herbicides have been registered in an increasing number of crops in Switzerland; recently, they have been introduced also in vineyards. Consequently, sulfonylurea herbicides play currently a role crucial in the chemical weed control in Swiss agriculture. Therefore, it is particularly important to prevent the spreading of resistances to this class of herbicides.
Concerning loose silky-bent, numerous biotypes of this species have already developed resistance to isoproturon, a substituted urea herbicide. Therefore, the risk of development of biotypes with multiple resistances is existent. Such an occurrence would lead to very difficult weed situation, especially in cereals.
Resistance mechanisms to cyhalofop-butyl in a biotype of Echinochloa phyllopogon (Stapf) Koss. from California
Summary
The mechanism(s) of resistance, namely changes in absorption, translocation, and metabolism, were studied in cyhalofop-butyl (CB) resistant and susceptible biotypes of Echinochloa phyllopogon (Stapf) Koss. Differences in absorption rates between the biotypes were detected; about 50 % of applied [14C]CB was absorbed by the S biotypes from 12 to 24 hours after application (HAA) while in the R biotype it reached 30 %. Biotypes did not differ in the amount or rates of CB translocated, with 98 % of applied [14C]CB remaining in the treated leaf.
The investigation for metabolism of absorbed CB in the plants proved five times less cyhalofop acid and 2 times more polar metabolites in the R biotype 6 HAA than in the S biotype. By 24 HAA, 4.2 % of the total CB absorbed had been converted to cyhalofop acid and 76.71 % to polar metabolites in the R biotype, vs. 20.82 % and 58.39 %, respectively, for the S biotype. The reduced herbicide absorption and the increased rate of herbicide metabolism correlated with herbicide resistance. It is concluded that the basis of resistance to CB in the resistant biotype E. phyllopogon is a reduced absorption through the cuticle and an increase in cyhalofop acid metabolism.
Field study on the occurrence of ground beetles and spiders in genetically modified, herbicide tolerant corn in conventional and conservation tillage systems
Summary
The habitat choice and population dynamics of arthropods depends highly on microclimate (particular combinations of temperature, humidity and light) and food availability. In agro-ecosystems, abundance can differ locally according to small scale characteristics, influenced in particular by the soil cultivation methods. There are various ways to cultivate soil, including conventional ploughing (PL) and conservation tillage (CT). The latter is a more protective of soil and friendlier to arthropods. Under ct conditions, the crop can be directly planted into a mulch layer which contains varying elements of macro- and mesofauna, thus providing a wide choice of prey for beneficial arthropods.
The objective of this study was to analyse and compare the impact on weed control and arthropod abundance of conventional and conservation tillage methods under different herbicide regimes. The study was conducted between 2002 and 2005 on continuously planted Roundup Ready® (RR) corn. Due to the very good efficacy of the active ingredient Glyphosate, weeds can be controlled in a more flexible time frame compared to e.g. the use of residual herbicides. Weed ground cover might be higher in RR crops for a longer period of time, thus providing favourable environmental conditions for a lot of arthropods.
Pitfall trapping was used to determine the abundance of ground-dwelling arthropods (carabids and spiders). The results show a clear difference between the two soil cultivation methods with regard to the number of individuals per species and the total number of species present. In the ct system, more individuals were trapped than under ploughed conditions, probably due to the higher ground cover of weeds (GUD) and higher food availability.
Weed control is necessary in agricultural fields to obtain maximum crop yield. Irrespective what method is used, highly efficacious weed control may diminish arthropod density due to habitat loss. In CT systems there is per se a longer period of favourable conditions for arthropods.
The results of this multi year study indicate that the combination of ct and herbicide tolerant corn has a positive impact on biodiversity. On the other hand, even though weeds and winter rye as intercrop are well controlled with the herbicide treatments, yield in the CT plots could not always reach the level in the ploughed system. The reason for this effect might be the higher water consumption of the winter-hardy intercrop that leads to less available water for corn in spring.
Studies on wild oat ( Avena fatua L.) resistance to fenoxaprop-P
Summary
Avena fatua L. is one of the most aggressive weeds in South-Eastern Poland. A very high abundance of this species in arable fields, connected with continuous usage of the same herbicides, may be the cause of herbicide resistance development. Three biotypes of wild oat, identified as resistant to field dose of fenoxaprop-P and one susceptible wild oat biotype from South-Eastern Poland were tested in the experiment. A dose-response test with five different doses of fenoxaprop-P was established and resistance index (RI) was calculated. Additionally, measurements of chlorophyll a fluorescence were conducted 48 and 72 h after fenoxaprop-P spraying.
The resistance index for the biotypes MIECH, SZAR and WIAZ was: 8.12, 7.58, 4.31, respectively. All resistant biotypes showed a lower decrease of root biomass, in response to growing fenoxaprop-P dosages, compared to the susceptible biotype SUSC. Also a decrease of the Fv/Fm ratio of the biotypes MIECH and SZAR was detected 48 hours after spraying with fenoxaprop-P.
Common chickweed ( Stellaria media L.) populations resistant to photosystem II inhibiting herbicides in Poland
Summary
The aim of this research was the identification of common chickweed (Stellaria media) populations, to be resistant to herbicides such as derivatives of triazines, ureas, uracils, pyridazinones, benzothiazoles and phenylcarbamates.
The research was conducted using monitoring tests. During five years (2000-2004) plants (leaves) and seeds of chickweed were collected from fields in South-West Poland. On these fields farmers cultivated through 3-10 years, usually in monoculture, maize, sugar beet and cereals (mainly winter wheat) and intensive chemical weed control by herbicides was used.
Resistance of biotypes was diagnosed by biological tests (evaluation of phytotoxicity, measurement of fresh and dry plant mass and calculating of resistance index) and fluorescence method.
Authors described resistance and cross-resistance of Stellaria media biotypes to different herbicides, such as atrazine, simazine, cyanazine, metamitron, linuron, chlortoluron and bentazone.
Alterations in amount of chlorophyll as indicator of resistance for Chenopodium album L. and Amaranthus retroflexus L. to atrazine
Summary
Resistance in weeds, as a natural phenomenon or caused by herbicide application, is a major challenge for science and agricultural production. Nevertheless, a small number of plants is naturally resistant or has developed a resistance caused by a natural selection process. Stress factors such as the use of herbicides results in development of resistant species by selection pressure. Slow uptake and translocation of herbicides, faster metabolization and/or the isolation of “foreign” molecules in certain tissues, structural changes in the target sites and others influencing factors are mechanisms of survival. Many research projects have been trying to find adequate physiological or morphological parameters for the determination of weed resistance to herbicides. For herbicides inhibiting photosynthesis, the most reliable parameters for the determination of weed resistance are bleaching effects as well as changes in plant dry mass and chlorophyll fluorescence. Therefore, the main objective of this study was to test the validity of measuring changes in the amount of chlorophyll as an indicator for the sensitivity/resistance of Chenopodium album L. and Amaranthus retroflexus L. to atrazine. The resistance was investigated using susceptible weed populations from Great Britain as well as weed populations from Great Crljeni and Belgrade. The total amount of chlorophyll was determined by a non-destructive method (SPAD meter-chlorophyll readings obtained with the Minolta-502 SPAD meter) and a destructive methode (extraction by dimethylphormamide). The validity of both methods was evaluated and the amount of chlorophyll and its fluorescence was correlated. Results showed that by measuring the amount of chlorophyll in both ways it was possible to distinguish between sensitive and resistant weed populations. A correlation between the amount of chlorophyll and changes in fluorescence could not be not confirmed.
Chlorsulfuron resistance in silky bent-grass ( Apera spica-venti (L.) Beauv.) in the Czech Republic
Summary
Control failures of Apera spica-venti in winter cereals fields are frequently encountered by farmers across the Czech Republic. Seeds of A. spica-venti from 40 accessions were collected to test them for resistance to ALS-inhibiting herbicides. The offspring of these populations were investigated using both whole plant bioassays and biochemical assays. The biotypes were compared with a susceptible biotype originated from Switzerland. Five biotypes were evaluated as highly resistant to chlorsulfuron in whole plant bioassays with RF (resistance factors) ranging from 6.7 to 1815. A treatment of the resistant biotypes with 1920 g per ha of chlorsulfuron reached an efficacy of only 30 %. For those five biotypes the difference of ALS activity in biochemical assays proved a target-site resistance as being involved in the resistance phenomenon.
Cross-resistance profile of metamitron-resistant Chenopodium album L. biotypes from sugar beet
Summary
In recent years, in several of the Belgian sugar beet growing regions, farmers have been confronted with unsatisfactory control of fat hen (Chenopodium album L.) by metamitron, a key herbicide in the modern low rate weed control programs in sugar beet. Greenhouse bioassays conducted on reference C. album populations and on “suspected” populations from sugar beet fields where poor fat hen control had been observed, revealed that all “suspected” populations were resistant to metamitron. These metamitron-resistant biotypes were all cross-resistant to atrazine.
Since cross-resistance, particularly negative cross-resistance or reversed resistance, is known to play a major role in resistance management, other herbicides used in sugar beet and/or in rotational crops were tested to determine the cross-resistance profile of metamitron-resistant biotypes. Greenhouse bioassays were conducted using herbicides from different chemical families representing different modes of action.
Cross-resistance was found for metribuzin, lenacil and chloridazon, all HRAC Group C1 herbicides that inhibit photosynthesis at PS II. The metamitron-resistant C. album populations examined showed negative cross-resistance to S-metolachlor (HRAC Group K3: inhibition of cell division), prosulfocarb (Group N: lipid synthesis, not ACCase, inhibition), aclonifen and clomazone (both Group F3: inhibition of carotenoid biosynthesis).
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