Spread of dangerous and adventitious weeds in Heves county.
Twenty years' observations of the occurrence and spread of weed species in this county of north Hungary are summarized. Sporadic occurrence is reported for the following species: Abutilon theophrasti, Asclepias syriaca, Chenopodium vulvaria and Amaranthus crispus. The species Bifora radians, Apera spica-venti, Amaranthus albus, A. lividus and A. blitoides appear locally but can have significant effects. Sorghum halepense occurred once but was successfully eradicated. Occurrence of Ambrosia elatior [A. artemisiifolia] has increased in the last 20 years. Though Bromus sterilis and Lactuca serriola occur sporadically throughout the county, they have become more numerous only in recent years.