POPULATION-DYNAMICS OF CRENATE BROOMRAPE (OROBANCHE CRENATA) IN FABA BEAN (VICIA-FABA)

Progression of crenate broomrape population density (PD, number of eme rged plants m(-2)) in faba bean was studied over 8 yr in Spain. Spatia l dispersion and effect of climatic conditions on parasite population growth rate (PGR) also were studied. With repeated cropping of faba be an, infestations of crenate broomrape increased from an initial PD of 0.15 to an average of 26, with a maximum of about 40 to 45. The averag e population growth rate (PGR, ratio between the PD of any 2 consecuti ve years) was approximately 3. However, this figure varied widely amon g localities and years, from 0.8 to 7.7. A highly significant relation ship (P = 0.01) was found between PGR and rainfall and soil temperatur es during December to February, months of crop vegetative growth. Disp ersion of crenate broomrape infestations mainly followed direction of crop rows, most likely due to the effect of tillage and harvesting ope rations, which were the same direction as sowing.