Magnesium sulfate deficiency and manganese sulfate deficiency are rarely fatal in palms. And correcting the deficiency may take two or more years.
Symptoms of Mg deficiency
i) In feather palms, broad chlorotic (yellow) bands along the margins with the central portion of the leaves remaining distinctly green
ii) In fan palms the chlorosis may appear as broad yellow bands along the margins of individual leaflets or the leaf as a whole.
iii) Symptomatic leaves will never recover.
Mild/Moderate: In neutral to alkaline soils use magnesium sulfate preferably the less soluble prilled kieserite form in addition to routine applications of the 8-2-12-4Mg maintenance fertilizer.
Severe: Supplement regular 8-2-12-4Mg applications by broadcasting magnesium sulfate (preferably in the prilled kieserite form) at rates of 2 to 5 pounds per palm 4 to 6 times per year under the canopy. Stagger regular and supplemental applications by 6 weeks.
Emerging leaflets are chlorotic with longitudinal necrotic streaking. Leaflet tips become necrotic, withered and curled giving the leaf a frizzled appearance commonly called “frizzletop.”
On coconut palm, necrotic leaflet tips fall off and the leaf has a singed appearance. On all affected palms, growth stops and newly emerging leaves consist solely of necrotic petiole stubs. Palm death often follows.
Supplement regular soil applications of 8-2-12-4Mg with routine applications of soluble manganese sulfate on soils. Foliar application of
0.3 lbs of manganese sulfate in 10 gallon of water gives quicker response. Soil application rates range from as low as 8 oz for a small palm to 8 lbs for a large palm growing on a limestone soil.