Q. My pygmy date palm has small, yellow spots on the leaves. What disease is this?
F.G., Miami Beach
If the spots are translucent (light can be seen through them), it is not a disease but potassium deficiency. This deficiency is very common on palms in South Florida. Potassium is rapidly leached for our soils and if the proper fertilizer is not being applied or at the correct rate, this deficiency shows up.
Use 8-2-12 + 4 percent magnesium palm fertilizer for all your palms. This fertilizer is also good for all plants in your landscape. It’s available at fertilizer suppliers; your county extension office has a list.
For mild to moderately potassium-deficient palms, an application of the above named fertilizer every three months during the growing season should be sufficient to treat and prevent K deficiencies. Treatment of K-deficient palms may require one to two years or longer, since the entire canopy of the palm may need to be replaced with symptom-free leaves. Removal of discolored older K-deficient leaves on a regular basis has been shown to accelerate the rate of decline from this disorder and can result in premature death of the palm.