Yield Losses in Soybeans Caused by Bacterial Tan Spot. J. M. Dunleavy, Research Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, 317 Bessey Hall, Iowa State University, Ames 50011. Plant Dis. 68:774-776. Accepted for publication 27 February 1984. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1984. DOI: 10.1094/PD-68-774.

In a preliminary field test, cupric hydroxide was effective as a protectant in the field against Corynebacterium flaccumfaciens, the cause of soybean bacterial tan spot, in uninoculated, susceptible Clark soybeans. It failed, however, to eradicate the disease in inoculated plants. The disease spread in both inoculated and unsprayed rows. In other trials, seed yield losses to tan spot ranged from 0.0 to 18.8%. Mean yield losses of 12.5% in 1979, 0.0% in 1980, and 4.3% in 1981 were measured at three locations, and a mean yield loss of 7.7% was measured at one location in 1978.