It is estimated that during the past 25 years black stem rust has damaged small-grain crops in Colorado to the extent of 335.000 bushels annually. Barberry eradication and other control measures have materially reduced rust losses in recent years. Stem rust is caused by a parasitic fungus that lives for a time each spring on the leaves of certain species of barberry. Spores produced on the barberry attack wheat, oats, barley, rye and about 75 different kinds of grasses. In this State barberry bushes have proved to be the most important source of early stem rust infection. Epidemies of stem rust involving areas of several square miles may originate from a single barberry bush. In addition to constituting an early spring source of infection the barberry is a possible breeding ground for new parasitic races of the stem rust fungus which may attack varieties of grain that are highly resistant to races now prevalent. There are three varieties of barberry common to Colorado: the common or European variety (B. vulgaris), the native barberry (B. fendleri), and the Japanese barberry (B. thunbergii). The common barberry and the native barberry are both susceptible to attack by the stem rust fungus. The Japanese barberry is immune. The State is cooperating with the U. S. Department of Agriculture in vigorous campaign to exterminate the common European barberry completely in Colorado, and to destroy the native barberries wherever they grow in or adjoining cultivated lands. The work has been carried on since 1918, and excellent progress has been made, especially during recent years through the use of Federal funds appropriated for unemployment relief. Many locations of barberry have been reported as a result of demonstrations given before school children and other organizations. Educational work conducted in advance of the survey has proved successful in obtaining information about localities in which grain rust has occurred and which are infested with barberry bushes. It is difficult to kill barberry bushes by digging or pulling, as sprouts often develop from root fragments left in the ground. Either common salt, salt brine, or “calcium chlorate” when properly applied will kill barberry bushes and eliminate danger of sprouting. Occasionally, stem rust spores carried by the wind from neighboring States reach Colorado in time to injure grain crops before they mature. However, infection from this source usually appears 2 to 3 weeks later than that which develops near local barberry bushes. To reduce losses from stem rust: (1) Eradicate all rust-spreading barberry bushes, (2) select for seed rust-resistant varieties of grain recommended by the Colorado Agricultural Experiment Station, and (3) plant spring wheat just as early as the soil can be properly prepared.

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