on the land. It is thought to have little effect on native fauna, although it may sometime be eaten by farm livestock. It may cause photosensitisation in susceptible animals. There is a report of its roots (rhizomes) being possibly poisonous to pigs. and the alkaloids it contains may be poisonous to horses in sufficient amounts. There are also reports of it being eaten by sheep and pigs to control it without reported problems. Chemistry Bindweed contains several alkaloids which are toxic for mice, including pseudotropine, and lesser amounts of tropine, tropinone, and meso-cuscohygrine. Economic impacts Although it produces attractive flowers, it is often unwelcome in gardens as a nuisance weed due to its rapid growth and choking of cultivated plants. It was most likely introduced into North America as a contaminant in crop seed as early as 1739, and became an invasive species. Its dense mats invade agricultural fields and reduce crop yields; it is estimated that crop losses due to this plant in the United States exceeded US$377 million in the year 1998 alone. It is one of the most serious weeds of agricultural fields in many temperate regions of the US. Control and management Bindweed is difficult to eliminate. Roots may extend as far as nine feet deep, according to one source, or 30 feet, according to another. New plants may sprout from seeds that are up to 20 years old. New plants can also form from root runners and root fragments. Methods for controlling bindweed include: Physical removal: Bindweed can be controlled by pulling it out by hand or plowing it up every three weeks, for three up to seven years. Mulching: Applying a thick barrier to block sun may control bindweed. Soil solarization for six to nine weeks in California was found to kill seedlings entirely, and control adult plants, but only for three weeks after treatment. Boiling water, placed on the plant, only practical for small areas. Biological control: Some insects and mites can eat, distort or stunt bindweed, but do not fully control it. Grazing: In Minnesota, sheep are able to consistently completely rid an infested pasture of the bindweed in two seasons, but only when the pasture is used to grow annual grains. In general, plant species which grow vigorously in the winter and early spring are best at smothering emerging shoots. It can be controlled by glyphosate. Other herbicides usually recommended for