We investigated the relationship between lygus plant bugs and the buckwheat crop in Manitoba, Canada. Small numbers of adult Lygus lineolaris appear on buckwheat crops in late July and give rise to a developing generation of nymphs in August. Migration from other crops can result in large adult populations in September. An insecticide application in late July or early August resulted in yield increases ranging from 12-78% in five different trials over three years, applications in September did not significantly affect yield. Caged buckwheat plants were much more severely damaged by lygus bug nymphs than adults, and the flowering stage was more vulnerable than later stages with developing seed. Nymphs attacking plants during flowering significantly decreased seed weight, flower and seed numbers; and increased percentages of dry flowers and shriveled seeds.