MODELING THE DEMOGRAPHY OF CRENATE BROOMRAPE (OROBANCHE CRENATA) AS AFFECTED BY BROAD BEAN (VICIA-FABA) CROPPING FREQUENCY AND PLANTING DATE

A mathematical model of crenate broomrape populations in broad bean as affected by cropping frequency and planting dates in the absence of c renate broomrape control practices was constructed using previously re ported data. In consecutive broad bean cropping, broomrape populations reached a maximum infection severity (D) of 62, 47, and 30 emerged br oomrape m(-2) for early (mid-October), intermediate (mid-November), an d late (mid-December) planting dates, respectively. The maximum D valu es were reached earlier as planting dates were brought forward, taking from 4 to 6 yr, starting from very low initial infections (D less tha n or equal to 0.2 emerged broomrape m(-2)). If broad bean was cropped every 3 yr, 15, 21, and 27 yr were needed, respectively, according to the model, to reach the maximum D for the three planting dates conside red. A sensitivity analysis was conducted to determine the effect of c hanging the values of the main demographic parameters in broomrape lif e cycle (germination, attachment, and seed loss) on the output of the model under different management strategies (planting dates and croppi ng frequency). Generally, an increase in seed attachment and a decreas e in seed loss affected broomrape population dynamics. Between the TWO processes evaluated, the time taken to reach the maximum infection se verity (D) was less sensitive than the maximum broomrape population va lues. Model predictions were validated using results from long-term fi eld studies at the late planting date sown every year. Simulated value s generated good predictions (R-2 = 0.82).