Corn poppy is the most widespread broadleaf weed infesting winter cereals in Europe. Biotypes that are resistant (R) to both 2,4-D and tribenuron-methyl have evolved in recent decades, thus complicating their chemical control. In this study, field experiments at two locations over three seasons were conducted to evaluate the effects of different weed management strategies on corn poppy resistant to 2,4-D and tribenuron-methyl, including crop rotations, delayed sowing and different herbicide programs. After 3 yr, all integrated weed management (IWM) strategies reduced the initial density of corn poppy, although the most successful strategies were those which either included a suitable crop rotation (sunflower or field peas), or had a variation in the herbicide application timing (early POST or combining PRE or early POST and POST). The efficacy of IWM strategies differed between both locations, possibly due to different population dynamics and the genetic basis of herbicide resistance. Integrated management of multiple herbicide–resistant corn poppy is necessary in order to reduce selection pressure by herbicides, mitigate the evolution of new R biotypes, and reduce the weed density in highly infested fields.

Nomenclature: 2,4-D; tribenuron-methyl; corn poppy, Papaver rhoeas L. PAPRH; sunflower, Helianthus annuus L.; field pea, Pisum sativum L.