|I get this black slimy stuff on my Impatiens and it kills them. How do I stop it.|
|Without inspecting the plant, it's difficult to diagnose the problem. However, impatiens are susceptible to Phytophthora, a fungal disease, which is sometimes called crown rot. The fungus attacks at the base of the plant. Once you notice the symptoms, the vascular system has already collapsed. Phytophthora can sometimes be avoided by planting your impatiens right at soil level (don't plant too deeply) and by keeping mulch materials away from the stems of the plants. These two steps will help keep the stems dry and less susceptible to fungal diseases. Other possibilities are mealbugs and whiteflies.
Mealybugs are wingless insects that suck the sap from impatiens, causing the leaves to turn yellow, distort and fall off. Mealybugs excrete a sticky, sweet substance called honeydew that attracts ants and also causes a black fungus to appear on the underside of leaves. Patches of a white cottony material are another sign of mealybug infestation on impatiens.
Whiteflies are another sap-sucking insect and also secrete honeydew like mealybugs. These insects have yellowish bodies, white looking wings and are found on the underside of the impatiens leaves. Once enough damage has been done, leaves will dry up, turn yellow and fall off the plant. Ants on or around the plant are a sign of whitefly infestation, as well as a black, sooty fungus on the leaves.
Hope this information helps you determine just what is going on with your impatiens.