02234nas a2200145   4500008004100000245011300041210006900154300001300223490000700236520166200243100002201905700001501927700001701942856012901959       1999                        eng d00aSurvey of common sunflower (Helianthus annuus) resistance to imazethapyr and chlorimuron in northeast Kansas0 aSurvey of common sunflower Helianthus annuus resistance to imaze  a510 -5140 v133 aImazethapyr resistance in common sunflower (Helianthus annuus) was confirmed in 1996 in a field near Rossville, KS. In 1997, common sunflower achenes were collected within a 20-km radius of the field with known resistance to determine if resistance was present in nearby fields or if resistance had spread to the native population on the roadside. Collections were made from 14 soybean (Glycine max) fields, one corn (Zea mays) field, and 11 roadsides. Achenes from Konza Prairie Research Natural Area, a prairie that had received no herbicide applications in the past 25 yr, served as the susceptible control. Common sunflower seedlings were treated in a greenhouse with 71 g ai/ha imazethapyr and 11 g ai/ha chlorimuron. In all 15 fields sampled, at least 1% of the common sunflower exhibited an intermediate response to imazethapyr or chlorimuron. In 13 fields, at least 1% of the plants were resistant to imazethapyr, and in all 15 fields, at least 1% of the plants were resistant to chlorimuron. Ten roadsides had common sunflower that showed intermediate response to imazethapyr or chlorimuron. At least 1% of the plants from seven roadsides were resistant to imazethapyr or chlorimuron. Common sunflower collected from fields with repeated applications of imazethapyr showed more resistance to imazethapyr than to chlorimuron. Nomenclature: Chlorimuron, 2-(((((4-chloro-6-methoxy-2-pyrimidinyl)amino)carbonyl)amino)sulfonyl)benzoic acid; imazethapyr, 2-(4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1-H-imidazol-2-yl)-5-ethyl-3-pyridinecarboxylic acid; common sunflower, Helianthus annuus L. 3 HELAN; corn, Zea mays L.; soybean, Glycine max (L.) Merr1 aBaumgartner, J.R.1 aKhatib, Al1 aCurrie, R.S.  uhttp://lter.konza.ksu.edu/content/survey-common-sunflower-helianthus-annuus-resistance-imazethapyr-and-chlorimuron-northeast