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Integrated weed management strategies which combine mechanical weed control, high crop densities, competitive varieties and reduced fertilizer inputs may reduce the need for herbicides to control P. rhoeas. Mechanical weeding using a spring-tine weeder was most effective in autumn in trials in organic winter wheat (Welsh et al., 1996). P. rhoeas is only moderately competitive against wheat and increasing crop densities significantly reduces biomass (Wilson et al., 1995) and seed production (Wilson et al., 1988). High levels of mineral fertilization favour P. rhoeas such that reduced inputs of NPK reduce its competitive effects on crop yield (Borowiec et al., 1986; Baylis et al., 1992).
Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:
P. rhoeas is reported as a weed of 23 crops in 43 countries (Holm et al., 1997). It is a serious or principal weed of wheat and winter wheat in the UK, France, Germany, Hungary, Iran, Italy, Morocco, Poland and Spain, and of barley in Greece, Iran, the former Soviet Union and Spain. It also a serious weed of lentils and lucerne in Spain; peas in Ireland and Greece; oil seed rape in the UK, France and Spain and sugar beets in Italy, Spain and Turkey (Holm et al., 1997). Cesari and Catizone (1975) reported P. rhoeas as the most abundant broad-leaved weed in Italy.
P. rhoeas is only moderately competitive. In spring sown cereals, Blackman and Templeman (1938) reported that even at densities as high as 500 to 1000 plants/m² no yield losses occurred as poppy seedlings emerged after the crop had established. The species competes more effectively with winter cereals (Wilson and Wright, 1990). In wheat, it was ranked eighth out of 12 weeds in terms of yield loss (Wilson and Wright, 1990) and in barley, Haizel (1972) found it to be only weakly competitive, being totally replaced by the crop after 12 weeks. Of 11 weed species growing in oilseed rape it was the second most competitive in terms of yield reduction (Lutman et al., 1995).
P. rhoeas acts as an alternative host to a range of economically important crop pathogens. These include beet yellows closterovirus, beet mild yellowing luteovirus and beet western yellows luteovirus (Stevens et al., 1994), artichoke Italian latent nepovirus and turnip mosaic potyvirus (Camele et al., 1991), potato virus X [Potato X potexvirus] (Kaczmarek, 1985), Leveillula taurica (Ullasa and Rawal, 1984) and broad bean wilt fabavirus (Schmelzer et al., 1975).