Molybdenum deficiency
Monday, 03 October 2005 09:47
This deficiency begins as a yellowing along poinsettia leaf margins, especially on the younger leaves (those on the middle of the plant and upward). Leaf margins become brown and necrotic. Leaves may also pucker downwards. Molybdenum deficiency resembles magnesium deficiency, except that the thin, marginal band of chlorosis is expressed from the leaf tip to the leaf base. Symptoms vary depending upon cultivar. Symptoms on Marblestar (see photo) are striking, but symptoms on other cultivars may be more subtle or lacking. Be sure to check your media pH on a regular basis. Molybdenum deficiency is more problematic when the pH is low (pH of 5.3 or lower).
Many of the poinsettia fertilizer blends contain sufficient molybdenum. If not, corrective supplemental drenches with either ammonium or sodium molybdate are needed. Corrective, foliar sprays of sodium molybate may also be applied as weekly sprays at 0.2 ppm. Foliar sprays are best applied in the morning to increase plant uptake and decrease the risk of injury.
Photo: Molybdenum deficiency on Poinsettia
Rich McAvoy and Leanne Pundt
