Black stem rust is an important disease of wheat. It has a wide host range including wheat, oats, barley, rye, timothy, wild and grasses and barberry. It is caused by the fungus Puccinia graminis. The fungus is heteroecious, alternating from cereal to barberry or Mahonia. While the fungus is coexistent with wheat through out the world, the disease causes most damage in moderately moist areas and in moist seasons in areas with low average rain fall. Eradication of barberry in northern regions is an important strategy to control black stem rust.
The common barberry was brought to North America by early settlers. Barberries made an excellent hedge because their dense growth and sharp spines discouraged penetration by livestock and poultry. In America the fruit became a favorite for sauces, jellies, wines, and preserves, and the bark was used as a source of yellow dye. Thus, the barberry became established in areas where it was a close neighbor to the small grain cereals, and both were moved by farmers as agriculture spread west in the early 1800s.
After the disastrous epidemic of 1916, laws against the growing of barberry were passed in the important wheat-producing states of South Dakota and North Dakota (1917); Michigan, Minnesota, Nebraska, and Colorado (1918); and Illinois, Indiana, Iowa, Montana, Ohio, Wisconsin, and Wyoming (1919). A cooperative federal and state program on barberry eradication was started in these states in 1918; Washington in 1923; Missouri, Pennsylvania, Virginia, and West Virginia in 1935; and Kansas in 1955.
Barberry eradication breaks the rust cycle to prevent local outbreaks of stem rust. The Barberry Eradication program was supplemented in 1919 by the issuance of Federal Quarantine No. 38 to prevent the interstate movement and reestablishment of susceptible barberries. A Federal program was established to test species and cultivars of Berberis, Mahonia, and Mahoberberis for reaction to P. graminis. At present, black stem resistant cultivars are allowed to be used as ornamentals. (Adapted from Alan. P. Roelfs. Effects of Barberry Eradication on Stem Rust in the United States. 1982. Plant Disease 66:177181.)
Identification of Cultivars
Cultivars of Japanese barberry (Berberis thunbergii) are popular ornamental garden shrubs. More than 40 cultivars of barberry with varied leaf color and plant habit are commercially available in the U.S. It can be very difficult to distinguish between cultivars based purely on morphological characteristics. Currently, researchers are using new molecular tools to distinguish between various species and cultivars and several scientific papers have been published.