Effects of the potato aphid Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae) on oilseed flax, and stage-specific thresholds for control

application date application foliaire chemical control control de insectos crop losses crop yield date de traitement dimethoate dimetoato economic thresholds etapas de desarrollo de la planta fecha de tratamiento foliar application insect control insect pests insecte nuisible linum usitatissimum losses lutte chimique macrosiphum euphorbiae manitoba perte pest insects plant developmental stages population density rendement rendement des cultures rendimiento rendimiento de cultivos treatment date yields