Weed control in direct-seeded pea and lentil

Direct seeding of pea (Pisum sativum L.) and lentil (Lens culinaris Medik.) crops is increasing in popularity in western Canada. Weed control strategies for these two crops are limited in a conventional tillage system; in a direct-seeding system, weed control options become even fewer. The herbicide ethalfluralin is commonly used for weed control in pea sown in a conventional tillage system, but it is not registered for use in direct-seeding systems. Surface application or shallow incorporation of ethalfluralin and triallate/trifluralin (10:4) could offer broad spectrum weed control in direct seeded pea and lentil. The level of weed control, crop tolerance and the economic suitability of the use of the dinitroanilines in direct-seeded pea and lentil was assessed. Results of experiments conducted at two locations near Saskatoon in 1995 and 1996 indicate that surface applications of ethalfluralin and triallate/trifluralin (10:4) offer similar and acceptable grassy weed control. However, ethalfluralin surface applied at rates less than 1.4 kg ai ha-1 did not provide acceptable control of wild oat when the wild oat population was high. Ethalfluralin applied in combination with a spring glyphosate bum-off treatment, followed by post-emergent metribuzin in lentil and MCPA-Na salt in pea, resulted in better broadleaf weed control than ethalfluralin applied in combination with fall-applied metribuzin. Post-emergent broadleaf weed control options were also more economical than fall-applied weed control options. Pea and lentil tolerance to reduced incorporation of ethalfluralin and triallate/trifluralin (10:4) was excellent. Glyphosate did not interfere with nitrogen fixation in either pea or lentil. The use of ethalfluralin and triallate/trifluralin (10:4), in combination with glyphosate applied in the spring and a post-emergent application of metribuzin in lentil and MCPA-Na salt in pea, has potential for broad spectrum weed control in direct-seeded pea and lentil in western Canada