The reproduction of a Wyoming population of Heterodera schachtii was determined for resistant trap crop radish (Raphanus sativus) and mustard (Sinapis alba) cultivars, and resistant and susceptible sugar beet (Beta vulgaris) cultivars in a greenhouse (21 degrees C/16 degrees C) and a growth chamber study (25 degrees C). Oil radish cultivars also were field tested in 2000 and 2001. In the greenhouse study, reproduction was suppressed similarly by the resistant sugar beet cultivar Nematop and all trap crop cultivars (P </= 0.05). In the growth chamber study, the radish cultivars were superior to most of the mustard cultivars in reducing nematode populations. All trap crops showed less reproduction than Nematop (P </= 0.05). In both studies, Nematop and all trap crops had lower Pf than susceptible sugar beet cultivars HH50 and HM9155 (P </= 0.05). In field studies, Rf values of radish cultivars decreased with increasing Pi of H. schachtii (r(2) = 0.59 in 2000 and r(2) = 0.26 in 2001). In 2000, trap crop radish cv. Colonel (Rf = 0.89) reduced nematode populations more than cv. Adagio (Rf = 4.67) and cv. Rimbo (Rf = 13.23) (P </= 0.05) when Pi was lower than 2.5 H. schachtii eggs and J2/cm(3) soil. There were no differences in reproductive factors for radish cultivars in 2001 (P </= 0.05); Rf ranged from 0.23 for Adagio to 1.31 for Commodore for all Pi.