mildew like Erysiphe betae and viruses such as beet ringspot and beet curly top virus. Taxonomy Some sources treat Polygonum arenastrum as a subspecies or variety of Polygonum aviculare, while others differentiate. Eradication In the home garden, common knotweed is easy to get rid of by hand pulling. Covering garden beds with landscaping fabric and then mulch is a good way to keep knotweed from taking over. If the seeds do germinate in the mulch cover, they are easy to remove. Herbicides are also an option. Pre-emergent herbicides, those that prevent the seed from germinating, are effective, but the area must first be free of weeds for this type of herbicide to work. Post emergent herbicides, those that kill the growing plant by spraying the green leaves of the plant, may be effective if applied when the plant is very young. To prevent this weed, the soil should be aerated and well-drained. Young weeds should be pulled before they set seed. References External links Jepson Manual Treatment University of California @ Davis IPM Calphotos Photo gallery, University of California @ Berkeley photo of herbarium specimen at Missouri Botanical Garden, collected in Missouri in 1994 arenastrum Flora of Europe Plants described in 1857