Dissemination of the quarantine weeds of the genus Ambrosia in the steppe zone of Ukraine

The article presents the results of many years of research for the period 2003-2020, which were aimed at studying the dissemination and expansion of plant groups of quarantine species of Ambrosia weeds in the eastern steppe of Ukraine. It has been established that the intensive dissemination of the species of the quarantine ragweed weed occurs both naturally and anthropically. Monitoring of the dissemination and growth of ragweed species is noted in all types of phytocenoses of the steppe. The increase in the areas of dissemination of aggressive species of ragweed weeds poses a widespread threat to all plant populations. Studies show a tendency to increase the number of ragweed plants in such plant groups as agrophytocenoses, phytocenoses of planted forests, phytocenoses of urban areas, meadows and pastures. For the  period 2011-2002  the number of ragweed plants increased in meadows by 7.5 times, in pastures by 14.8 times, in agrophytocenoses by 2.95 times, in phytocenoses of urban areas by 1.68 times, in phytocenoses of planted forests by 1.28 times. Due to the lack of control over the dissemination and appropriate eradication measures, the largest increase in the number of ragweed plants over the past 10 years has been observed in meadows and pastures. It is recommended in phytocenoses of planted forests and urban areas in meadows and pastures, total mowing of ragweed plants before their flowering 5-7 times during the growing season in order to prevent replenishment of the seed stock of this weed in the soil during the growing season.