ケシ
"Papaver somniferum" shows a very slow development in the beginning of its vegetation period. Due to this fact the competition of weeds is very high in early stages. It is very important to control weeds effectively in the first 50 days after sowing. Additionally "Papaver somniferum" is rather susceptible to herbicides. The pre-emergence application of the herbicide chlortoluron has been shown to be effective in reducing weed levels. However, in the last decade the weed management of "Papaver somniferum" has shifted from pre-emergence treatments to post-emergence treatments. Especially the application of the two herbicides mesotrione and tembotrione has become very popular. The combined application of those two herbicides has been shown to be recommendable for effective weed management in "Papaver somniferum". Sowing time (autumn or spring), preceding crop and soil texture are important variables influencing the weed species composition. A highly abundant weed species in "Papaver somniferum" fields was shown to be "Papaver rhoeas". "Papaver somniferum" and "Papaver rhoeas" belong to the same plant family, which impedes the chemical control of this weed species. Therefore, weed management represents a big challenge and requires technological knowledge from the farmer. In order to increase the efficiency of weed control not only chemical weed control should be applied but also mechanical weed control.