Problem: Boston Ivy Leaf Spot
This plant disease is caused by a fungus (Guignardia bidwellii f. sp. parthenocissi) that infects only Boston ivy and Virginia creeper. Spores are released from the small black fruiting bodies that form in the spots. They are spread by splashing rain to other leaves, where they germinate in drops of water to cause more spots. Leaves must be continuously wet for 10 to 15 hours for infection to take place. The fungus is closely related to one that causes a disease of grapes known as black rot. The disease spreads most rapidly during extended periods of warm (60° to 90°F), wet weather.
If possible, pick off infected leaves. Keep leaves dry if possible. Rake up and either compost or destroy all leaves in the fall.