Answer: There are two diseases that can affect ivy, especially if it is watered by overhead sprinklers. Bacterial leaf spot causes the conditions you describe, and is rampant in warm, moist conditions. The leaf spots look water-saoked at first, then turn brown and fall out. If you find a reddish margin around the spots, this is the likely culprit. To stop the spread, cut off all affected plant parts, and try to avoid overhead irrigation. Keep the plant healthy by feeding lightly with an 8-8-8 fertilizer. The second possibility is a fungal disease; same treatment. The symptoms include angular spots rather than round spots. I'd suggest cutting out the infected plant leaves and stems, fertilizing lightly, and avoid overhead watering if at all possible.
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