COMPARATIVE FIELD REACTION OF SUGAR-BEET AND SEVERAL CRUCIFEROUS CROPS TO NACOBBUS ABERRANS

Varieties of oil seed rape (Brassica napus L, and B. campestris L.), f orage Brassicas (kale, B. oleracea L.; turnip, B. rapa L.; rape, B. na pus L.; and a turnip x Chinese cabbage hybrid, B. rapa L, x B. pekinen sis L.) and sugarbeet cyst nematode-resistant trap crops (radish, Raph anus sativus L., and mustard, Sinapis alba L.), all in the Brassicacea e (Cruciferae) family and sugarbeet (Beta vulgaris L.) in the Chenopod iaceae family, were evaluated for root galling in naturally infested f ield plots after 5 wk in 1992 and after 14 wk in 1993 for comparative reaction to the false root-knot nematode (Nacobbus aberrans Theme and Alien), a root parasite of sugarbeet in eastern Wyoming. Nacobbus aber rans did not induce galls on any cruciferous crop. Incidence of sugarb eet with root galls was 41% in 1992 and 82% in 1993, while severity wa s 1.1 galls/root and 3.3 galls/root, respectively. Increased incidence of galling in 1993 appeared to be due to a longer period of evaluatio n with optimum soil temperature [3291 and 2423 growing degree days (GD D) base 5 degrees C at 2.5 and 10.2 cm soil depth in 1993 compared to only 1102 and 870 GDDs in 1992]. Additional symptomatic hosts of N. ab errans included several weeds growing in the test site; common lambsqu arters (Chenopodium album L.), kochia (Kochia scoparia L.), and Russia n thistle (Salsola iberica, Sennen and Pau), all in the Chenopodiaceae family, common purslane (Portulaca oleracea L.), in the Portulacaceae family, and puncturevine (Tribulus terrestris L.), in the Zygophyllac eae family. Common purslane represents a new weed host of N. aberrans in North America. Lambsquarters was used as a bioassay for N., aberran s during both years to verify presence of N. aberrans in plots of entr ies with asymptomatic roots. Incidence of lambsquarters with galls was 36% in 1992 and 60% in 1993 while severity was 0.8 and 2.0 galls/root , respectively.