Biology, ecology and management of Raphanus raphanistrum L.: a noxious agricultural and environmental weed.

Weeds are a major constraint to crop production and a barrier to human efforts to meet the ever-rising global demand for food, fibre and fuel. Managing weeds solely with herbicides is unsustainable due to the rapid evolution of herbicide-resistant weeds. Precise knowledge of the ecology and biology of weeds is of utmost importance to determine the most appropriate nonchemical management techniques. Raphanus raphanistrum L. is an extremely invasive and noxious weed due to its prolific seed production, allelopathic potential, multiple herbicide resistance and biological potential. R. raphanistrum causes high crop yield losses and thus has become one of the most troublesome agricultural and environmental weeds. R. raphanistrum could exchange pollen with herbicide-tolerant canola and could become an environmental threat. This weed has evolved resistance to many herbicides, and relying exclusively on herbicide-based management could lead to severe crop loss and uneconomical cropping. Although reviews are available on the ecology and biology of R. raphanistrum, significant changes in tillage, weed management and agronomic practices have been occurring worldwide. Therefore, it is timely to review the status of noxious weeds in different agro-ecological zones and management scenarios. This review focuses on the response of R. raphanistrum to different cultural, mechanical, biological, chemical and integrated management strategies practiced in various agro-ecosystems, and its biological potential to thrive under different weed management tactics. In addition, this review facilitates a better understanding of R. raphanistrum and describes how weed management outcomes could be improved through exploiting the biology and ecology of the weed.

Biology and management of Avena fatua and Avena ludoviciana: two noxious weed species of agro-ecosystems.

Avena fatua and Avena ludoviciana are closely related grass weed species infesting a large number of crops around the world. These species are widely distributed in diverse agro-ecosystems from temperate to sub-tropical regions due to their unique seed traits, successful germination ecology, high competitive ability, and allelopathic potential. A. fatua is more widespread, adaptable, and problematic than A. ludoviciana. Both these species infest major winter and spring crops, including wheat, oat, barley, canola, maize, alfalfa, and sunflower, causing up to 70% yield losses depending on crop species and weed density. Chemical control has been challenged by large-scale herbicide resistance evolution in these weed species. A. fatua is the most widespread herbicide-resistant weed in the world, infesting about 5 million hectares in 13 countries. The use of alternative herbicides with different modes of action has proved effective. Several cultural practices, including diverse crop rotations, cover crops, improved crop competition (using competitive cultivars, high seed rates, narrow row spacing, altered crop geometry), and allelopathic suppression, have shown promise for controlling A. fatua and A. ludoviciana. The integrated use of these cultural methods can reduce the herbicide dose required, and lower dependency on herbicides to control these grasses. Moreover, integrated management may successfully control herbicide-resistant populations of these weed species. The use of integrated approaches based on the knowledge of biology and ecology of A. fatua and A. ludoviciana may help to manage them sustainably in the future.