Cultural control of Phalaris minor Retz. (Little seed canary grass) in wheat: a review

The continuous adoption of rice-wheat cropping system in the Indo-Gangetic plains especially Punjab and Haryana, has led to the serious problem of Phalaris minor in wheat. Isoproturon remained most popular herbicide with farmers for about two decades as it provided effective control of P. minor in wheat. However, in the recent years the problem of P. minor has increased alarmingly because of development of resistance to isoproturon. The use of alternate herbicides (clodinafop and sulfosulfuron) reduced the infestation of P. minor, but the risk of development of resistance to these herbicides and the growing concerns of environmentalists over increasing herbicide load per unit area has forced the weed scientists for exploration of cultural methods of weed control. In this review, the important cultural practices or agronomic manipulations that can be used to reduce the infestation of weeds particularly P. minor in wheat has been discussed. Replacing wheat with berseem, potato, sunflower, raya, gobhi sarson, field pea, winter maize, sugarcane etc. can help to eliminate or reduce the problem of P. minor. Advancing the sowing date of wheat helps to avoid the first and the most competitive flush of P. minor. Planting pattern such as closer row sowing (15 cm) or cross sowing or bidirectional sowing (22.5 cm x 22.5 cm) modifies wheat canopy structure and thus increases the weed smothering potential of the crop. Heavy stand of the crop effectively smothers P. minor. Bed planting of wheat is more advantageous compared to traditional flat plating of wheat with regard to reduction in the intensity of P. minor. Deep ploughing may reduce P. minor population by burying seeds to a depth from where seedlings are not likely to emerge whereas the effect of zero tillage on reducing the infestation of P. minor is contrary. Proper placement of fertilizers i.e. side drilling helps to increase significantly grain yields of wheat by lowering the dry matter accumulation by P. minor as compared to broadcast method. The growth and development of arable weeds particularly P. minor is directly related with soil moisture i.e. more soil moisture more weed growth. Competitive wheat cultivars belonging to T. aestivum group provide better competition than durum wheat varieties for smothering weeds particularly P. minor.