Biology and management of Phalaris minor in rice-wheat system

Phalaris minor Retz. (Littleseed canarygrass) is a pernicious weed, which infests several crops during the winter season, particularly the wheat crops in rice-wheat sequence. Considering the limitations of cultural and chemical methods of weed control, the understanding of its biology with respect to different environmental, edaphic and management factors may offer a useful key to strengthen weed management strategies. This review considers various aspects on dormancy, viability and agro-ecology with emphasis on management practices in host and succeeding crops. Due attention has been given to the approaches required to manage the resistant biotypes under present conditions and hence to avoid further escalation of the epidemic. The various studies indicate that P. minor utilizes beneficially the prevailing environmental and management conditions of both the wheat and succeeding rice crop in rice-wheat system for its survival and growth. Its seed is highly sensitive to variable moisture and temperature regimes for germination and exhibits tolerance to anoxia during anaerobic respiration in rice. Tillage options, residue management, spatial-temporal considerations and other factors influence the seed dynamics, pattern and depth of emergence and growth of P. minor. A comprehensive and conceptual understanding of these aspects may provide useful guidelines in formulating cautious and opportunistic weed management strategies. (C) 2004 Published by Elsevier Ltd.