The common barberry, (Berberis vulgaris) and many of its horticultural varieties as well as certain other species of Berberis, Mahonia, and Mahoberberis are the alternate host plants of the disease black stem rust, caused by the organism Puccinia graminis. Black stem rust attacks wheat, oats, barley, rye, and many other cultivated and wild grasses, often resulting in material financial loss to growers of these crops in Washington. Without access to alternate host plants, Puccinia graminis cannot reproduce, and black stem rust is eliminated or greatly decreased. The director of agriculture, under authority granted by chapters 17.24, 15.13 and 15.08 RCW, has determined that the regulation and exclusion of rust susceptible varieties of barberry and related Berberis, Mahonia, and Mahoberberis species is necessary to protect agricultural crops of the state of Washington.