The Use of Ascochyta caulina Phytotoxins for the Control of Common Ragweed

Common ragweed, Ambrosia artemisiifolia Bess. is an alien weed of North American origin that became invasive in Europe. Although the main concern regarding this plant is its impact on human health, due to abundant production and easy spread of its highly allergenic pollen, A. artemisiifolia is also increasingly becoming a major weed in agriculture, being very competitive with crops and difficult to manage. Previous research had lead to the identification of a mixture of three toxins from the culture filtrates of Ascochyta caulina (P. Karst.) Aa & Kestern, a fungal pathogen of Chenopodium album L., having high toxicity against both host and non-host plant leaves, with lack of antibiotic and zootoxic activities. Recently, a two-year research project named ECOVIA has been approved and financially supported by the Regional Governorate of Lombardy (Italy). The main aim of the project is to develop the technologies to obtain a natural herbicide based on the bioactive toxins produced by A. caulina, and to study the possibility of its practical use. Among the selected target weeds, A. artemisiifolia showed an evident response to the toxin application, probably due to the presence of trichomes on the leaves that allow a quick absorption of the metabolites, with fast appearance of leaf necrosis and plant desiccation. Greenhouse bioassays as well as open field experiments clearly indicate the lethal effects on the young ragweed plants.