The foxtail palm (Wodyetia bifurcata), a tropical tree native to Australia, is prized for its fast growth and reaches its mature size within 12 years, according to the University of Hawaii. This palm is extremely resilient and hardy, but unlike many other palms, it rarely suffers from pests or diseases. On rare occasions, the foxtail palm may need treatment with a fungicide to help it beat a fungus-based disease.
Leaf spot symptoms chiefly consist of circular, dark lesions on the foxtail palm's foliage. Nitrogen and iron deficiencies make the palm more susceptible to the fungus that causes leaf spots. The leaf spots should regress once the palm's full vigor is restored through the regular application of a standard palm-targeted fertilizer. If not, a standard fungicide like copper spray will kill this disease. Gardeners can minimize the chances of their foxtail palm contracting leaf spot by watering the palm directly at its base rather than spraying the entire tree and getting its foliage wet.
Petiole blight creates rust- or brown-colored streaks along the length of the foxtail palm's foliage stems (petiole). It usually first appears on the oldest leaves on the tree. If left untreated, it can kill off the entire frond. Spraying the palm with a fungicide formulated with mancozeb or iprodione will eliminate the fungus that causes the disease.
The lethal yellowing disease is common in palms like coconut trees. Though foxtail palms are resistant to yellowing, according to the University of Hawaii, they can occasionally succumb to it. Symptoms start when the foxtail palm's nuts drop prematurely, followed by the fronds turning yellow and dying off. If left untreated, the disease will kill the entire palm within six months. Phytoplasma bacteria causes lethal yellowing, commonly spread by insects, according to the University of Florida. Injections of oxytetracycline-HCL, obtained from some garden stores and nurseries, can help a foxtail palm recover.