دم‌روباهی کشیده (Alopecurus myosuroides)، یک علف‌هرز باریک‌برگ رو به‌گسترش در استان فارس

Change in weed flora, especially in agroecosystems is a common phenomenon. The emergence of problematic weeds such as wild barley (Hordeum spontaneum) and false jagged-chickweed (Lepyrodiclis holosteoides) or herbicide-resistant weeds in recent years are prominent examples of the changes in weed flora in Iran. Black-grass (Alopecurus myosuroides) is a grass species belonging to the Poaceae family where changes in its frequency have been reported in some countries such as Denmark. The origin of black-grass is likely the Mediterranean region, and from there, it has spread throughout Europe and Western Asia. Now, it is a major grass-weed in winter cereal crops in Northwestern European agricultural systems. Black-grass prefers heavy, clay, and moisture-retentive soils. It is an annual, outcrossing (wind-pollinated) species propagated and spread only by seeds. The shed seeds have innate dormancy. The dry and high-temperature conditions in summer can release seed dormancy so that around 80% of seeds germinate in autumn. Black-grass can cause up to 40% yield reduction in winter wheat. More importantly, black-grass is a high herbicide-resistant risk weed species and it is the number one herbicide-resistant weed in Europe, now ranked among the fifteen most important herbicide-resistant weeds worldwide. This weed, in addition to being present in wheat fields of Fars province, is also found in wheat fields of at least ten other provinces, including Ardabil, East Azerbaijan, Zanjan, Qazvin, Isfahan, Golestan, Ilam, Khuzestan, Chaharmahal and Bakhtiari, and Lorestan. Among these ten provinces, the highest level of infestation by this weed has been observed in the wheat fields of Zanjan province. Field surveys and personal communication with local experts and farmers showed that black-grass is spreading in fields of Fars province, Iran, especially in areas where winter wheat-rice crop rotation is common. More importantly, field surveys by the authors showed that the development of resistance to ACCase inhibitor herbicides in black-grass might be possible as clodinafop-propargyl and pinoxaden failed to control the black-grass plants in a winter wheat field in Marvdasht, Fars province. However, laboratory and greenhouse studies are needed to confirm this hypothesis. To avoid experiencing the previous bitter event of wild barley distributed throughout the country, more attention must be directed toward the control, management, and research of this weed species. Exploiting the experience of European researchers who have been coping with this problem for around half a century, especially researchers from Rothamsted Research in England, might be valuable. For example, the use of cultural control methods such as deep plowing, crop rotation, delayed drilling, reduced dependence on high-risk herbicides (e.g., ACCase, ALS inhibitors), and the use of mixtures and sequences of herbicides with different modes of action are suggested by British scientists for managing this weed species, especially for those herbicide-resistant populations.