Spatial distribution and rnapping of crenate broornrape infestations in continuous broad bean cropping

ApdoA084, 14080-Córdoba, Spain ".Geosrarisrical rechniques were used re describe and mar me sparial disrriburion of crenare broomrape popularions parasirizing broad bean ayer 6 yr (from 1985 re 1990). In me firsr year, me sparial disrriburion was random, bur from 1986 re 1989, crenare broomrape popularions were clearly aggregared. The crenare broomrape" infecrion severiry {I5: number of emerged broomrape m-2) increased"every year, from an average of 0.45 in 1985 re 29.4 in 1989, wim a slighr decrease me following year (15 = 27.4). 5pherical funcrions provided rhe bese fir because rhe cross-validarica crireria were accomplished in all silldy cases. Kriged esrimares were used re draw conrour maps of me popularions. Abour 34.3, 43.3, and 74.3% of me field Flor surface exhibired an 15 ~ 1 (economic mreshold) in 1985, 1986, and 1987, respecrively, and nearly 100% of me afea exceeded me economic mreshold from 1988 re 1990; 1985 and 1986 were key years for control of me parasiric weed popularion. The percenrage of infesred afea ar differenr 15 imervals in each year's mar obrained by kriging was used re estímate me percenrage of yield losses in each infesred afea (Y,J wirh me equarion: YA = A * Ymax * (1 15 * 0.124), where A is me infesred afea ar a given 15 inrerval and Ymax is me expecred broomrape-free broad bean yield. Yield losses under differem 15 intervals were compared wim yield loss attriburable re a uniform disrribution of crenate broomrape. Resulrs showed mat yield loss assuming a uniform disrriburion of crenate broomrape was clearly overesrimated, which is imporram re avoid overuse of herbicides."