Submitted to: Plant Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/7/2004
Publication Date: 2/1/2005
Citation: Peterson, P.D., Leonard, K.J., Miller, J.D., Laudon, R.J., Sutton, T.B. 2005. Prevalence and distribution of common barberry, the alternate host of Puccinia graminis, in Minnesota. Plant Disease. 89:159-163. Interpretive Summary: Stem rust, potentially the most destructive disease of spring wheat in the Northern Plains of the U.S., has been controlled for more than 50 years by breeding resistant wheat varieties and by the elimination of common barberry as a source of new stem rust races in the Northern Plains. The sexual stage of the stem rust fungus can develop only on common barberry. Before eradication of barberry, the populations of races of stem rust in the field changed continuously and it was nearly impossible for wheat breeders to maintain resistance in new spring wheat varieties for more than a few years. The barberry eradication program was terminated in the 1980s before all the known barberry sites had been certified free of barberry seedlings or sprouts. We surveyed 72 sites in Minnesota where barberry bushes had been destroyed but where the necessary follow-up studies had not been completed to ensure that no new seedlings or sprouts had emerged after the parent bushes were destroyed. Barberry plants were found in 32 of these 72 sites. Nearly all of the newly emerged barberry plants were found in southeastern Minnesota where little wheat is grown, but one bush was found near a wheat field in a major wheat-producing county of northwestern Minnesota. Our results show that continuing efforts are necessary to find and destroy barberry bushes before they reproduce and spread into wheat-producing areas of the Northern Plains. If barberry continues to spread, the sexual stage of the stem rust fungus could reappear and new stem rust races with high virulence to formerly resistant wheat varieties could cause severe epidemics with 15-20% yield losses in the Northern Plains.
Technical Abstract: A Federal and State program operated from 1918 until the 1980s to eradicate barberry (Berberis vulgaris), the alternate host of Puccinia graminis, from the major areas of cereal production in the U.S. More than 500 million barberry bushes were destroyed nationally during the program; approximately 1 million bushes were destroyed in Minnesota. Some sites in Minnesota where barberry bushes were destroyed remained in the 'active' class when eradication was phased out in the 1980s. Active sites were defined as those on which there was still a possibility of emergence of barberry seedlings or sprouts arising from the parent bush. In the present study, from 1998 to 2002, 72 of the approximately 1,200 active sites in Minnesota were surveyed. Areas within 90 m of mapped locations of previously destroyed bushes were searched carefully at each site. Reemerged barberry plants were found on 32 sites. The reproductive status and GPS coordinates were recorded for each reemerged bush. More than 90% of the barberry bushes were found in counties with less than 400 ha of wheat per county, mostly in southeastern Minnesota, but one bush was found in a major wheat-producing county in northwestern Minnesota. Reemergence of barberry may serve as a source of new wheat stem rust races in future epidemics.