Invasive weeds: the case study of ragweed control in France France

1. Stop to invasive weeds / Photo ACTA Reynoutria japonica / Photo ACTA Phytolacca americana/ Photo ACTA Ambroisia artemisifolia in Sunflower / Photo ACTA Invasive weeds:the case study of ragweed control in France France MODULE C18

2. Introduction : Background • Ragweed is an invasive weed • Yield losses in summer cropslike sunflower • Capacities to develop into non-agricultural environments • Very allergenic Photos ACTA

3. Artemisia vulgaris Anthemis arvensis Identification • Seed • Young plants Beware of confusions ! • Adults Ambrosia artemisifolia Drawings and Photos ACTA and INRA

4. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Germination Vegetative development Pollen transfer Fructification Seed production Male inflorescence Female flowers Plantlet Seed = Achene Stage ofdevelopment Flowering plant Biological cycle Ragweed in Rhône-Alpes (France) Drawings INRA

5. Photo ACTA Dissemination • Very low dispersal abilities • Spread by agricultural tools • Spread by contaminated soils Drawings and Photos ACTA and INRA

6. Development • Spring and summer crops • Intercropping period: Cereal, peas and rapeseed stubbles • Fallows poorly maintained • Abandoned agricultural land • Roadsides, construction sites Photos ACTA and CETIOM Photos ACTA & CETIOM

7. Sowing Emergence Post-emergence herbicide Only false-seed bed No chemical treatment :no selectivity Only on tolerantcultivars Control in spring crops Weeder Hoeing In inter-row Pre-emergence herbicide Post-emergence herbicide Pre-emergence herbicide Not easyin gravels soils Post-emergence herbicide Post-emergence herbicide Pre-emergence herbicide Post-emergence herbicide Photos ACTA and CETIOM

8. Control at harvest and in intercropping period AT HARVEST • Harvest the contaminated fields after all the others • Clean the harvester machines DURING INTERCROPS • One intervention before flowering • To avoid pollen emission • One intervention before graining • To avoid the reconstitution of the seed bank • Cultivation :Stubble ploughing • Non-selective herbicides at low rate Photos ACTA

9. Control in non-agricultural environment • Priority to prevention control • No seeds introduction with contaminated soils • Vegetalization of road, railway sides,… • Mulches in greenspaces • Possibilities of curative control • If ragweed is non dominant : • Practice a high shearing (15 cm) • Use selective herbicides • Favour natural vegetalization • If ragweed is dominant : • Try to eliminate plants with non-selective herbicides ora low mowing • Repeat until raqweed becomenon dominant and then favorize vegetalization Photos ARVALIS & ACTA

10. Buffer zone / Photos ACTA Conclusion • Use of IPM General principles • Preventive measures • Beware to not import seeds from contaminated areas or with contaminated implements • Rapid vegetalization in non agricultural areas • Preferring non-chemical methods • Mechanical control is possible in agricultural and non-agricultural areas • Correct choice of pesticide and limitation of rate • Beware of pesticides transfer • You can reduce the herbicides rate on young plants