First record of Milk thistle (Silybum marianum, Asteraceae) as a potential invasive weed species in Addis Ababa city, Ethiopia

Abstract

Early detection, identification and management of invasive weed species are important works in Integrated Pest Management program. Since 2020, Milk thistle, Silybum marianum, an invasive weed species, has been observed widely in urban green spaces and roadsides in Addis Ababa city, Ethiopia. This study aimed to determine the current distribution status of the weed in urban green areas of Addis Ababa city, Ethiopia to plan future management activities. Weed surveys were conducted across 42 urban green sites located in Yeka, Lemi Kura, Bole, Nifas Silk-Lafto, Kolfie Keraniyo, Akaky Kality and Gullele sub-cities during the main rainy season from June to September 2023. The urban green areas were selected by using purposive sampling techniques. Field observations confirmed that Silybum marianum can invade and colonize wide habitats and is a highly competitive invasive weed to other important native plant species. High weed density rates and dense stands of weeds were recorded in the 34 urban green areas. The survey result strongly suggests fast integrated weed management options such as mowing/tilling, weeding before the plant goes to seed, cutting (stems and/or seed heads), and burning (collected plant parts and/or seed heads) into a prepared burrow were done to minimize the spreading of the weed and its ecological impacts.