The passion flower vine (Passiflora sp.) is native to the Americas and primarily grown for its colorful blossoms and egg-shaped, edible fruit. It thrives in USDA hardiness zones 8 through 11. Even a well-maintained passion flower vine can succumb to various fungal and bacterial diseases. If left untreated, a lush passion flower vine will lose its foliage, wither and die.
Blight caused by the Phytophthora fungus starts as unaesthetic black spots on the passion flower's foliage. If fruits are present, the blight can also mark the fruit. As the disease progresses, it can lead to irreversible wilting and loss of foliage. Treat the disease with a standard fungicide that's labeled for use against downy mildew. Apply treatment every 10 days during extended periods of wet weather.
The Alternaria passiflora fungus is the culprit behind brown spot disease. It's common on species like the purple passionfruit and the yellow passionfruit, according to Purdue University. Limit the chances of your vine contracting the disease by avoiding overhead irrigation and only watering at the vine's base. Use fixed copper spray to kill the fungus.
Fusarium wilt is caused by the Fusarium oxysporum fungus. The disease is soil-borne and can be avoided by rotating crops. Growing passion flower vines during consecutive growing seasons increases the risk of fusarium wilt. Symptoms start with slight wilting, followed by the entire vine turning yellow and dying. Though standard fungicides can sometimes control the disease once it starts, they are often ineffective. You most likely will have to remove the entire plant.
Woodiness is the general term given to the effects of several different diseases, including the passionfruit woodiness virus and the alfalfa mosaic virus. Diseased vines will show yellow mottling or spots on their foliage and stems, while the passion flower's fruit will display thick, scar-like growths. The disease is most common from the fall to the spring. There is no known cure for the disease, according to the New Zealand Passionfruit Growers Association, and infected plants should be removed. Because the virus is often transmitted by aphids, regular treatments of insecticidal soap can reduce the chances of contracting this problem. The virus can also be carried on contaminated garden equipment. After removing a diseased vine, all garden implements should be dipped in vinegar to sterilize them.