Combining cutting and herbicide application for Ambrosia artemisiifolia control

The effect on Ambrosia artemisiifolia (common ragweed) of combining cutting and herbicide application was studied in pot experiments in Germany and Denmark in 2013. Single plants of common ragweed were established in 2 L pots in glasshouses. Two cutting treatments were conducted: cutting to 10 cm height at the beginning of male budding (BBCH 51-59) and no cutting. Clopyralid (in Germany: Lontrel 600, in Denmark: Matrigon), mesotrione (in Germany and Denmark: Callisto) and glyphosate (in Germany: Clinic, in Denmark: Roundup Bio) were applied at 4 doses at three different timings: on the day of cutting, one week and two weeks after cutting. The plants were harvested 5 weeks after the last herbicide application. At both sites clopyralid and mesotrione had a low efficacy on common ragweed when applied on developed plants with only minor differences in efficacy at the three timings. Application after cutting improved the efficacy of clopyralid at both sites and of mesotrione in Denmark. In Germany glyphosate had a higher efficacy on noncut plants in comparison to the cut plants, in Denmark it was vice versa. The highest dose of glyphosate provided higher control levels on developed plants than clopyralid and mesotrione at both sites. In Denmark the highest effects were obtained shortly after cutting with the maximum dose of each herbicide and declined with time between cutting and herbicide application. In summary the results demonstrated that herbicides can be applied shortly after cutting without loss of efficacy.Kombination von Herbizidapplikation und Schneiden zur Bekämpfung von Ambrosia artemisiifoliaIn Deutschland und Dänemark wurde in Gewächshausversuchen die Kombinationswirkung von Herbizid und Schnitt auf Ambrosia artemisiifolia (Beifußblättrige-Ambrosie) untersucht. Einzelpflanzen der Beifußblättrigen- Ambrosie wurden in 2 L Gefäßen im Gewächshaus angezogen. Zwei Schnittvarianten wurden durchgeführt: Schnitt der Pflanzen auf 10 cm Höhe zum Beginn der männlichen Blüte (BBCH 51-59) und kein Schnitt. Clopyralid (in Deutschland: Lontrel 600, in Dänemark: Matrigon), Mesotrione (in Deutschland und Dänemark: Callisto) und Glyphosat (in Deutschland: Clinic, in Dänemark: Roundup Bio) wurden mit 4 Dosierungen zu drei verschiedenen Zeitpunkten ausgebracht: am Tag des Schneidens, eine Woche und zwei Wochen nach dem Schnitt. Die Ernte der gesamten Pflanze fand 5 Wochen nach der letzten Herbizidapplikation statt. An beiden Standorten hatten Clopyralid und Mesotrione eine geringere Wirkung auf die ungeschnittenen Pflanzen, ungeachtet des Applikationszeitpunktes. Die Herbizidausbringung nach erfolgtem Schnitt verbesserte die Wirkung von Clopyralid an beiden Standorten und von Mesotrione in Dänemark. In Deutschland war die Wirkung von Glyphosat auf die ungeschnittenen Pflanzen besser als auf die geschnittenen, am dänischen Standort war es umgekehrt. Glyphosat mit der maximalen Dosis hatte an beiden Standorten eine bessere Wirkung auf ältere Pflanzen als Clopyralid und Mesotrione. In Dänemark wurde die höchste Wirkung kurz nach dem Schnitt mit der maximalen Dosis und jedem Herbizid erreicht, diese Wirkung nahm ab, je später die Herbizidapplikation nach dem Schnitt erfolgte. Zusammenfassend lässt sich festhalten, dass die angewendeten Herbizide kurz nach dem Schnitt ausgebracht werden können, ohne dass ein Wirkungsverlust zu verzeichnen ist

Fitness of ALS-Inhibitors Herbicide Resistant Population of Loose Silky Bentgrass (Apera spica-venti)

Herbicide resistance is an example of plant evolution caused by an increased reliance on herbicides with few sites of action to manage weed populations. This micro-evolutionary process depends on fitness, therefore the assessment of fitness differences between susceptible and resistant populations are pivotal to establish management strategies. Loose silky bentgrass (Apera spica-venti) is a serious weed in Eastern, Northern, and Central Europe with an increasing number of herbicide resistant populations. This study examined the fitness and growth characteristics of an ALS resistant biotype. Fitness and growth characteristics were estimated by comparing seed germination, biomass, seed yield and time to key growth stages at four crop densities of winter wheat (0, 48, 96, and 192 plants m-2) in a target-neighborhood design. The resistant population germinated 9–20 growing degree days (GDD) earlier than the susceptible population at 10, 16, and 22°C. No differences were observed between resistant and susceptible populations in tiller number, biomass, time to stem elongation, time to first visible inflorescence and seed production. The resistant population reached the inflorescence emergence and flowering stages in less time by 383 and 196 GDD, respectively, at a crop density of 96 winter wheat plants m-2 with no differences registered at other densities. This study did not observe a fitness cost to herbicide resistance, as often hypothesized. Inversely, a correlation between non-target site resistance (NTSR), earlier germination and earlier flowering time which could be interpreted as fitness benefits as these plant characteristics could be exploited by modifying the timing and site of action of herbicide application to better control ALS NTSR populations of A. spica-venti

The effect of nitrogen and glyphosate on survival and colonisation of perennial grass species in an agro-ecosystem: does the relative importance of survival decrease with competitive ability?

The ecological success of a plant species is typically described by the observed change in plant abundance or cover, but in order to more fully understand the fundamental plant ecological processes, it is necessary to inspect the underlying processes of survival and colonization and how they are affected by environmental conditions. A general ecological hypothesis on the effect of environmental gradients on demographic parameters is proposed and tested. The hypothesis is that decreasing fitness or competitive ability along an environmental gradient is associated with an increasing importance of survival for regulating the abundance of the species. The tested hypothesis is related to both the stress gradient hypothesis and whether the importance of competition increases along productivity gradients. The combined effect of nitrogen and glyphosate on the survival and colonization probability of two perennial grass species, Festuca ovina and Agrostis capillaris, which are known to differ in their responses to both glyphosate and nitrogen treatments, is calculated using pin-point cover data in permanent frames. We found that the relative importance of survival increased with the level of glyphosate for the glyphosate sensitive A. capillaris and decreased for the glyphosate tolerant F. ovina. Likewise, increasing levels of nitrogen increased the importance of survival for the relative nitrophobic F. ovina. Consequently, the proposed hypothesis was corroborated in this specific study. The proposed method will enable predictions of the effects of agricultural practices on community dynamics in a relatively simple setup eliminating the need to quantify all the interaction among the species in the plant community. The method will be immediately useful for the regulation of non-cultivated buffer strips between agricultural fields and semi-natural and natural biotopes such as hedgerows and waterways