Distribution of field bindweed and hedge bindweed in the USA

A survey of weed specialists and herbaria was conducted by mail with telephone follow-up in 1994 and 1995 to determine the distribution, abundance, and economic importance of field bindweed (Convolvulus arvensis L.) and hedge bindweed [Calystegia sepium (L.) R. Br.] (Convolvulaceae) in the continental USA. Field bindweed occurs at densities regarded as serious (greater than 1000 acres/county) in 957 counties, moderate (between 250 and 1000 acres/county) in 845 counties, and low (less than 250 acres/county) in 573 counties in 47 of the 48 contiguous states. Only Florida and the southern parts of states from South Carolina to Texas do not report its presence. Field bindweed infestations have increased since 1970 in several western states but have decreased in importance in most Great Plains states. Based on detailed crop loss data for 10 states containing 52% of the seriously infested counties, we estimated the value of crop losses due to field bindweed in the USA at more than $377 million/yr. Hedge bindweed occurs at densities regarded as serious in 101 counties, moderate in 1109 counties, and low in 553 counties in 43 states. Although not as widespread as field bindweed, hedge bindweed appears to have increased in abundance since 1969 and continues to be a localized problem in the midwestern and eastern USA.