A Case of Arsenical Injury to Tomato Plants

On August 15, 1921, the writer was called to examine the tomato plants in one of the experimental plots of the Iowa State College Horticultural Department which were dying from some unknown cause. Upon examination, many plants were found showing all stages of what appeared to be some wilt disease. The caretaker stated that the trouble was manifested at first by a wilting of the entire plant which was often followed in a few days by its death. Upon examination, the first plant revealed the presence of a small mite in large numbers. These were found throughout the lower portions of the main stem and it was thought at first that these acari were the cause of the trouble. Subsequent examinations of other affected plants failed to disclose the mite in all cases and it was evident that this species was a secondary invader. Doctor J. C. Gilman, of the Plant Pathology section, was called and took specimens to his laboratory for further tests. He reported later that he could isolate no pathogenic organism