Black Spots on Swedish Ivy

Viruses

• Impatiens necrotic spot virus (INSV) and tomato spotted wilt virus (TWV) are two closely related diseases that affect Swedish ivy. Both viruses are spread by the Western flower thrip. Symptoms include the appearance of brown or black spots on the leaves. Plants may also turn yellow, wilt or develop yellow or black ring spots. Since the symptoms are easily confused with other diseases, a definitive diagnosis must be made by a laboratory. Isolate infected plants until a diagnosis is confirmed. Infected plants should be destroyed since there are no cures for these diseases. The best way to keep your Swedish ivies from becoming infected is to control thrips.

Thrips

• Thrips are tiny insects that are only .07 inch long so they’re hard to see. Hold a sheet of white paper near your ivy and gently shake the plant. If your Swedish ivy is infested with thrips, they will appear as small dots on the paper. Use a magnifying glass to see them more easily. Male thrips are pale yellow and females are yellow and brown. Thrips acquire these viruses as larvae, but don’t spread disease until they feed on plants as adults. Control thrips with organophosphates, chlorinated hydrocarbons, macrocyclic lactone, or pyrethroids. Rotate insecticides so thrips don’t develop resistance to them.

Myrothecium

• Myrothecium leaf spot is a fungal infection that causes black or dark brown watersoaked spots to appear on the leaves. Fungal fruiting bodies called sporodochia appear in the dead areas on the undersides of leaves. The sporodochia, which are black, can develop a white fringe of mycelium. Myrothecium usually appears when leaves are wet and temperatures are between 70 and 81 degrees Fahrenheit. This fungus can survive in the soil or in plant debris and spreads by splashing water. Control myrothecium by avoiding injuries to plants since it easily infects Swedish ivy through wounds. Don’t overfertilize, because high levels of fertilizer may encourage this disease. Avoid wetting leaves when watering your plants. In severe cases, fungicides may be needed for control.

Pseudomonas

• Pseudomonas is a bacterial blight that causes dark gray dry spots to develop along the margins of the leaves. As the disease progresses, the spots grow larger and your Swedish ivy may drop its older leaves. There is no control for this disease. Isolating infected plants and keeping the leaves dry may slow down the spread of this disease.