Ivy Leaf Spot
Director of Research
Growing ivies outside is usually a fairly easy thing to do, but it can present difficulties that we do not see when growing ivies inside. Ivy leaf spot is one of these problems. Ivy leaf spot can be caused by a variety of fungus species as well as bacteria.
Fungus Leaf Spot can be caused by Colletotrichum trichellum, Amerosporium, Glomerella, Phyllosticta, and Ramularia. They appear as irregular tan to brown spots or may cause marginal browning of the leaf edges. This browning continues until the entire leaf is dead. As the disease progresses, you may see tiny dark brown to black dots within the spots. These are the fruiting bodies of the fungus. These create the spores that spread the fungus.
Bacterial Leaf Spot is caused by Xanthomonas campestris pv. Hederae. It first appears as a light green or water-soaked to oily circular spots. As the disease progresses the spots will enlarge and turn dark brown to black. There may also be a yellow to red halo around the spot. Petiole and stem cankers can also develop.
This all sounds terrible, but fortunately if caught early both of these diseases can be cured easily. Because both of these diseases need water on the foliage to infect, it is important to keep the foliage as dry as possible. Wet weather and overhead watering favor these diseases. If you must water overhead, do so early in the day so the foliage dries before night. Better yet use a soaker hose.
To control leaf spot disease, remove diseased leaves or stems as soon as they appear. It is also a good idea to remove old leaves and debris from the bed each spring before new growth begins. This may be all that is needed to stop the spread of these diseases.
If the removal of the effected leaves and stems does not control the disease you may need to apply a fungicide. For chemical control a copper-based fungicide is effective on both of these diseases. It can be used as a curative as well as a preventative measure. For specific recommendations for your area, consult your State agriculture extension office.