A specific physiological disorder of the recently matured leaves of Tagetes erecta has been demonstrated to be associated with high levels of iron and manganese in affected tissues. In previous work by the authors, the disorder was inducible and increased in severity with increasing levels of iron DTPA supplied to plants grown in peat-based media, but was much less severe when iron DTPA treatments were applied to plants grown hydroponically. At low concentrations of iron DTPA in solution, the occurrence of the disorder was more closely correlated with increased levels of manganese in leaf tissue than iron, Objectives of this study were to determine the effects of iron chelate (DTPA) on occurrence of the disorder and the availability of iron and manganese in the media in the absence of added manganese. Iron DTPA (1, 5, 15, and 20 ppm) was supplied to two cultivars of Tagetes erecta, `Voyager' and `First Lady', grown in a commercial peat-based media product under controlled environmental conditions. Concentrations of iron and manganese in leachate samples taken weekly, and in symptom and non-symptom tissue at harvest, and the progression of the symptoms in leaf tissue over time. will be discussed.