Decreases in Crop Production by Non-native Weeds, Pests, and Pathogens

The worldwide trade of agricultural products and high levels of disturbance and fertilisation make arable lands particularly vulnerable to biological invasions. Clearing for the development of arable land has been an unprecedented event that created a new and more homogeneous habitat which allowed many species to spread to become (sub) cosmopolitan weeds, pests, and pathogens. Through competition for light, water, and nutrients (weeds), or destruction of plant tissue (pests and pathogens), harmful organisms can potentially reduce crop yield by 10-40 % on average. Historically, some non-native species produced spectacular invasions and caused incalculable damage by annihilating crop production at large scales: for example, potato late blight, Phytophthora infestans, which was one of the factors causing the Irish Potato Famine, and the American vine phylloxera, Daktulosphaira vitifoliae, which devastated vineyards across the whole of Europe. Nowadays, it is estimated that non-native weeds, pests, and pathogens cause as much as US\$248 billion in annual losses to world agriculture, making this the sector most affected by the introduction of non-native species. The use of pesticides has long protected crop yield satisfactorily. However, because of the undesirable side effects that may be associated with pesticide use (e.g., development of resistant biotypes and water pollution), more integrated approaches to combat invasive species are needed, - including prevention (phytosanitary control) and cropping systems with higher potential for ecological regulation.