Polygonum hydropiper (Linn.) Spach is a competitive weed in many crops, especially in irrigated crops, rice, tea estates of north east India and other crops grown on poorly drained soils. Biological control of P. hydropiper using chrysomelid beetle Galerucella placida Baly, is an effective approach. Occurrence of G. placida has been reported from India, Bangladesh, Nepal, Sri Lanka, Myanmar, Thailand, Laos, Vietnam, Sumatra, Java, China and Australia. This book contains information related to biology, seasonal occurrence of adult diapause, comparative morphology of reproductive organs of diapausing and non-diapausing adult, host specificity, leaf consumption and nutritional indices etc. These information will help to formulate strategies to curb the polygonum weed effectively.