Avoid overhead irrigation and instead water near the base of the palm tree. This prevents excessive leaf wetness, which increases the chance of fungal diseases.
Sanitize pruning shears after each cut by wiping the blades with a rag dampened in solution of one part bleach to nine parts water. This helps stop the spread of any diseases from one part of the palm tree to another.
Remove and destroy all infected leaves from the foxtail palm, including any plant debris that has fallen to the ground.
Fertilize the foxtail palm every three months with a slow release 8-2-12-4Mg with micronutrients fertilizer. Apply 15 pounds of the fertilizer for every 1,000 square feet of the foxtail palm canopy. Palm trees that suffer from a nutrient deficiency are more likely to develop diseases and problems.
Dilute 0.5 to 2 ounces of a liquid copper fungicide concentrate in 1 gallon of water. Mix thoroughly before transferring the solution to a pump sprayer. Spray the infected foxtail palm with the diluted copper fungicide covering the entire tree including the underside of the leaves. Repeat the treatment at seven to 10 day intervals as needed.