Artemisiifolia Plants Research Articles

Reduced Invasiveness of Common Ragweed (Ambrosia artemisiifolia) Using Low-Dose Herbicide Treatments for High-Efficiency and Eco-Friendly Control.

Common ragweed (Ambrosia artemisiifolia) is an invasive annual weed that invades heavily disturbed habitats and natural habitats less disturbed by human activities with native plant species in need of protection. Achieving effective control of A. artemisiifolia for the protection of native organisms and the local ecological environment is an ongoing challenge. Based on the growth and development characteristics of A. artemisiifolia, we examined the effectiveness of herbicides in controlling this species and the optimal time for application in the field with the aim of reducing herbicide dosage. Additionally, we analyzed whether the efficiency of low-dose applications for controlling this species might improve with increasing native plant species richness. Our findings indicate that aminopyralid (33 g ai ha−1) was the most suitable herbicide for chemical control of A. artemisiifolia, with optimum application time being during vegetative growth (BBCH 32–35). Application of aminopyralid was found to kill approximately 52% of A. artemisiifolia plants, and more than 75% of the surviving plants did not bloom, thereby reducing seed yield of the population by more than 90%. Compared with the application of high-dose herbicide, the phytotoxicity of aminopyralid to native plants at the applied dose was substantially reduced. After 2 years of application, the relative coverage of A. artemisiifolia significantly decreased, with few plants remaining, whereas the relative coverage of native plants more than doubled, representing an eco-friendly control. Further, there was an increase in the A. artemisiifolia control rate in the plant community with higher native plant species richness at the same herbicide rates and a reduction in seed yield of A. artemisiifolia. Our findings help toward developing control measures to reduce the invasiveness of A. artemisiifolia with low-dose herbicides meanwhile protecting native plants, and then using the species richness of native plant communities to indirectly promote the effectiveness of low-dose herbicide application.

In-season leaf damage by a biocontrol agent explains reproductive output of an invasive plant species

One of the biggest challenges in classical biological control of invasive weeds is predicting the likelihood of success. Ambrosia artemisiifolia, a North American plant species that has become invasive in Europe, causes economic losses due to health problems resulting from its huge amount of highly allergenic pollen and as a weed to agricultural crops resulting from high seed densities. Here we assessed whether the pollen and seed output of the annual A. artemisiifolia (at the end of the season) is related to in-season abundance of, or damage by, the accidentally introduced biological control agent Ophraella communa. We monitored the growth and leaf damage of individually labelled A. artemisiifolia plants at four locations in Northern Italy and recorded abundance of different O. communa life stages at regular intervals. We found that the in-season level of leaf damage by O. communa consistently helped to explain seed production in combination with plant volume and site throughout the season. Feeding damage, plant volume and site also explained pollen production by A. artemisiifolia six weeks before male flower formation. At three out of four sites, plants with more than 10% leaf damage in mid-June or early July had a very low likelihood of seed formation. Leaf damage proved to be a better explanatory variable than O. communa abundance. Our results suggest that the monitoring of the in-season leaf damage can help to project the local impact of O. communa on A. artemisiifolia at the end of the season and thus inform management regarding the needs for additional measures to control this prominent invader.

The influence of Ambrosia trifida on vegetative production of A. artemisiifolia

Ambrosia artemisiifolia (common ragweed) and A. trifida (giant ragweed) are very important weed species that are invasive in Serbia and are often found in agricultural regions. When these weeds are present at high densities, crop yields can be significantly reduced or even completely destroyed. Unlike A. artemisiifolia, A. trifida is locally present in the Central Backa region (Vojvodina province), and it is expected that its area of distribution will expand in the future. Starting from the assumption that future distribution of A. trifida could take on larger proportions than now, the aim of this study was focused on examining the interaction between these two species. Experiments were conducted using the replacement design model, in which Ambrosia trifida/Ambrosia artemisiifolia per m2, were planted as density ratios of 10/0; 8/2; 4/6; 6/4; 2/8, and 0/10, in a completely randomized block system with four replications. The vegetative parameters (height and dry mass) of A. artemisiifolia were measured in July, August and September over a period of two years (2016 and 2017), and the results were statistically analysed in the Statistical Package for the Social Sciences (SPSS 23). In July 2016, the average height of A. artemisiifolia was in the range between 35.00 and 50.40 cm, in August it was from 68.00 to 95.50 cm, and between 83.75 and 99.80 cm in September. In the following season (2017), the corresponding values ranged from 56.19 to 78.50 (July), 98.38 to 125.50 cm (August) and 111.19 to 148.50 (September). An increase in the number of A. artemisiifolia plants and decrease in A. trifida counts per m2 caused an increase in the dry mass of A. artemisiifolia per plant. The dry mass of A. artemisiifolia ranged from 4.22 to 6.11 g/plant (July), 8.96 to 10.27 g/plant (August) and 7.04 to 19.53 g/plant (September). In the following season, these values ranged from 9.62 to 14.60 g/plant, 14.37 to 28.90 g/plant, and 23.43 to 40.47 g/plant in July, August and September, respectively. Minimum values of vegetative parameters were recorded in the treatment with 2 plants, and maximum in the treatment with 10 A. artemisiifolia plants/m2. This means that interspecific competition is more pronounced in this ragweed species than intraspecific competition.

Genetic structuring and diversity patterns along rivers – local invasion history of Ambrosia artemisiifolia (Asteraceae) along the Danube River in Vienna (Austria) shows non‐linear pattern

SummaryAmbrosia artemisiifolia is an annual weed from North America that nowadays is invasive in many countries worldwide. In Austria, numerous populations of A. artemisiifolia are located along the Danube River, especially along the ‘New Danube’ (Vienna). This area is characterised by ruderal and riparian sites, which are regularly flooded. To better understand the spread of A. artemisiifolia and its colonising behaviour along the Danube River, we analysed genetic structure and diversity based on 23 populations linearly arranged along the Viennese Danube riverbed and upstream, utilising the Amplified Fragment Length Polymorphism (AFLP) fingerprint method. We generated 284 polymorphic AFLP markers across 446 A. artemisiifolia plants. The genetic diversity within populations was higher (HW = 0.091) than among populations (HB = 0.007). This result indicates A. artemisiifolia introductions from similar mixtures of sources or spread from a single already mixed introduction. Within our local setting, we were unable to identify neither source or sink populations nor an obvious linear genetic structuring. Genetic among‐population differentiation was low to moderate (amova‐derived FST = 0.124). Lack of geographical structuring is indicative of highly dynamic gene flow, which is further supported by the absence of an isolation‐by‐distance pattern. Multiple introductions and non‐directional gene flow are most likely promoted by anthropogenic disturbance and human‐mediated dispersal. Our results demonstrate the ability and speed of A. artemisiifolia to settle in newly disturbed areas and the difficulties to predict invasion directions, as downstream river dispersal was negligible.

Molecular identification and pathogenicity assessment of a rust fungus infecting common ragweed (Ambrosia artemisiifolia) in its native North American range

A rust fungus collected from common ragweed (Ambrosia artemisiifolia) in Texas, USA, was identified as belonging to the Puccinia xanthii morphospecies based on its nrDNA ITS sequence. Pathogenicity studies carried out with this rust accession under quarantine conditions in the UK showed that the fungus was highly virulent on A. artemisiifolia plants from Australia. Recently, P. xanthii has been proposed as a potential classical biological control agent (CBCA) for common ragweed in its invasive range, focusing on Europe, despite previous doubts about its biocontrol potential. The results of the pathogenicity tests reported here support the suitability of this pathogen as a CBCA for common ragweed.

Food deprivation-dependent development and fecundity in Ophraella communa

Ophraella communa LeSage is native to North America and a biological control agent of the invasive weed Ambrosia artemisiifolia L. Since A. artemisiifolia plants grow old and die after September annually, O. communa suffers from food shortage. To understand the effect of food shortage or deprivation on population fitness of O. communa, the development and fecundity and hatchability of its progeny eggs were observed when larvae were offered A. artemisiifolia plants for either 3, 6, 12 or 24 hours daily. The results showed that larval food deprivation significantly influenced survival and developmental durations of larvae and pupae. Survival rates and developmental durations of larvae and pupae decreased and were prolonged significantly with decreasing time of larval daily food intake. Longevity and fecundity of adults shortened and decreased significantly with decreasing time of larval daily food intake. In addition, the hatch rates of progeny eggs decreased significantly with decreasing time of larval daily food intake. The present study suggests that food shortage is one of the most critical factors that suppresses O. communa populations. This can explain why field populations of the beetle decrease significantly with ageing and death of A. artemisiifolia plants after late September.

Management of roadside populations of invasive Ambrosia artemisiifolia by mowing

SummaryAmbrosia artemisiifolia (common ragweed) is a highly allergenic alien weed in Europe, which spreads rapidly along roadsides. Road verges are subject to frequent mowing, which further increases the spreading of the plants' seeds. Ambrosia artemisiifolia reacts to cutting by producing new shoots, which are able to develop flowers and ultimately new seeds. An effective mowing regime that would decrease the production of seeds and their dispersal is desirable to control the spread of the plant, but an appropriate way of mowing has yet to be found. In this study, we explored how the reproductive traits of A. artemisiifolia plants in seven spontaneous roadside populations reacted to the application of different mowing regimes over 3 years. The mowing regimes that were applied differed in the timing and frequency of cuttings. We found that the cutting regime, if appropriately timed, can strongly influence the production of male inflorescences (i.e. allergenic pollen), of female flowers (i.e. seeds) and had an impact on the phenological development of the plant. Based on our findings, we suggest that the optimal management of the plant along roadsides must be adjusted to its phenological development. The most effective mowing method of control consists of a first cut shortly before male flowering, to limit the quantities of released pollen, followed by subsequent cuts before the onset of new flowers on the resprouting lateral shoots.

EFFECTS OF SOIL SALINITY IN THE GROWTH OF AMBROSIA ARTEMISIIFOLIA BIOTYPES COLLECTED FROM ROADSIDE AND AGRICULTURAL FIELD

Morphological differences were observed between roadside (R) and agricultural field (F) biotypes of Ambrosia artemisiifolia, in which R-type seedlings were shorter and produced larger and heavier seeds under greenhouse grown conditions. Previous findings indicated that A. artemisiifolia R-types exhibited greater salt tolerance with respect to germination. However, the impact of biotype and salt tolerance on morphological variation has not been investigated in A. artemisiifolia plants. After performing replicated greenhouse experiments with both biotypes, it was shown that salinity level was a critical factor influencing both seedling and mature plant size and this response was dependent upon biotype. The R-type exhibited slight but significant increases in growth at low/mild salinity levels (50–100 mM) compared with non-saline conditions, while the F-type exhibited significantly reduced growth at the low/mild salinity levels. The reductions in growth of F-type plants in low/mild salinity were similar to those reductions of R-types observed in non-saline conditions. As both biotypes produced seeds at low/mild salinity levels, we conclude that low/mild salinity affects A. artemisiifolia plant size and overall growth rate, and secondly, certain F-type plants may acclimate to the roadside environment over time by reducing their size while producing larger seed under saline conditions. It is possible that this species may exhibit changes in morphology after several generations of exposure to saline roadside conditions. Toxicity due to salt treatment at high salinity (400 mM) was observed in both biotypes, whereas the R-type was more tolerant to both low and high salinity levels with respect to seed germination. Differential A. artemisiifolia growth responses which occur from seed germination to plant maturity may be partially attributed to its ability to tolerate saline soil conditions both under greenhouse and field conditions. This ability to tolerate saline conditions may be especially important in early spring when roadside soils experience increased salinity, caused by de-icing salt treatments applied during the winter season.

Spray retention, foliar uptake and translocation of glufosinate and glyphosate in Ambrosia artemisiifolia

Summary Ambrosia artemisiifolia plants exhibit stomata on both leaf surfaces and three types of trichomes: (i) small (<50 μm) spherical or ovoid, (ii) medium‐sized (50–100 μm) and (iii) long (100–200 μm) and sharp. Only the long and sharp trichomes were stained with AgNO3, indicating the presence of hydrophilic domains. Epicuticular waxes appeared amorphous, consistent with high levels of spray retention. Glufosinate was readily taken up by A. artemisiifolia leaves, with maximum uptake of >80% of the applied label, and half maximum uptake being reached within 6 h. The foliar uptake of glyphosate was nearly complete and half of it was attained after 3 h. Glufosinate and glyphosate were ambimobile and their translocation out of the treated leaves amounted to 13–16% and 11–15% of the absorbed radioactive label respectively. Glufosinate was mainly directed to the apical developing tissues, with less amounts reaching the tissues below the treated leaves. Glyphosate was directed towards the sink tissues (apical developing tissues and roots). The sensitivity of A. artemisiifolia to glufosinate and glyphosate can be explained by high spray retention, rapid and important foliar uptake, and appreciable migration out of the parts of the plant hit by the spray.

CO2 enrichment reduces reproductive dominance in competing stands of Ambrosia artemisiifolia (common ragweed)

Plants growing in dense stands may not equally acquire or utilize extra carbon gained in elevated CO(2). As a result, reproductive differences between dominant and subordinate plants may be altered under rising CO(2) conditions. We hypothesized that elevated CO(2) would enhance the reproductive allocation of shaded, subordinate Ambrosia artemisiifolia L. (Asteraceae) individuals more than that of light-saturated dominants. We grew stands of A. artemisiifolia at either 360 or 720 muL L(-1) CO(2) levels and measured the growth and reproductive responses of competing individuals. To test whether elevated CO(2) altered size and reproductive inequalities within stands, we compared stand-level coefficients of variation (CV) in height growth and final shoot, root, and reproductive organ biomasses. Elevated CO(2) enhanced biomass and reduced the CV for all aspects of plant growth, especially reproductive biomass. Allocation to reproduction was higher in the elevated CO(2) than in the ambient treatment, and this difference was more pronounced in small, rather than large plant positive relationships between the CV and total stand productivity declined under elevated CO(2), indicating that growth enhancements to smaller plants diminished the relative biomass advantages of larger plants in increasingly crowded conditions. We conclude that elevated CO(2) stimulates stand-level reproduction while CO(2)-induced growth gains of subordinate A. artemisiifolia plants minimize differences in the reproductive output of small and large plants. Thus, more individuals are likely to produce greater amounts of seeds and pollen in future populations of this allergenic weed.

Ecophysiology of Ambrosia Artemisiifolia: A Successional Dominant

Ambrosia arteinisiifolia L. dominates abandoned fields after spring plowing in many parts of the eastern United States. Its seeds germinate at or near the soil surface in early spring, and the cotyledons become green shortly after they emerge. They are photosynthetically active, with a net photosynthesis dark respiration ratio (P/R) of 1.9. The primary leaves are photosynthetically more active than the cotyledons with a P/R ratio of 3. Photosynthesis of young A. artemisiifolia seedlings is 21 mg C02 dm-2 hr-1 at 1,076 X 102 lux, 250 C, and 300 ppm CO2. They approach light saturation at 1,076 X 102 lux (1.1 cal cm-2 min-) and exhibit appreciable photosynthesis at temperatures from 5? to 350 C. Their rate of photosynthesis increases with an increase of the ambient C02 concentrations comparable to that measured near the soil surface in the field. Although seedling photosynthesis is quite sensitive to decreasing water potential (*J.) between 0 and -10 bars, there is no further decrease between -10 and -20 bars. Furthermore, at this range of 'P photosynthesis is about 20% of that at 0 bars. In a plowed field these seedlings experience high light intensities, appreciable variation in daily temperature, high CO2 concentrations due to its flux from the soil, and low water potentials since the roots are in the upper part of the soil. Field-grown, mature A. artemisiifolia plants do not light-saturate even at 1,076 X 102 lux. Their photosynthetic rate at optimum light intensity, temperature, ala, and 300 ppm C02 is about 35 mg C02 dm-2 hr-1. This high rate of photosynthesis is accompanied by a high rate of transpiration (3 g H20 dm-2 hr-1). Photosynthesis in these plants is sensitive to temperature and reaches a peak at 200 C. The effect of CO2 enrichment on the rate of photosynthesis is not as pronounced in mature plants as in seedlings. Photosynthetic rates decline sharply between -10 and -15 bars BILL; however, appreciable rates are maintained even at '' of -20 bars for several hours. Photosynthetic recovery from water stress is rapid after watering and is attributed to the very low total plant resistance to water transport (1 X 106 sec cm-1). Mature plants have moderate photorespiration since their CO2 compensation point is reached at 50 ppm C02. These data indicate that A. artemisiifolia can not only efficiently exploit the environmental resources of the field during seedling and mature plant stages of its life cycle but also effectively function under the sometimes extreme conditions encountered in the field. These ecophysio- logical attributes coupled with complex germination behavior and genetic plasticity enable the species to be a successful pioneer in early successional ecosystems where the environment can be severe and unpredictable.