Answer: The vast majority of leaf spots and leaf blights of palm are caused by fungi. In general, the symptoms look similar no matter which fungus is causing the spot or blight.
In general, the initial symptom for leaf spots is a small, water-soaked lesion. Within days, this lesion turns to varying shades of yellow, gray, reddish-brown, brown or black. The colored lesions may be surrounded by a halo or ring of tissue that is a different color.
While fungicides may be useful to prevent further spread of the disease, they are merely a supplement to water management, sanitation, injury prevention and good palm nutrition. Fungicides alone will not solve the problem. It is critical to understand that fungicides do not cure the leaf spots already present. Once a spot occurs, it will remain for the duration of the life of that leaf. Fungicides are used to prevent further spread of the disease by protecting leaf tissue that has not been infected by the fungal pathogens.
Active ingredients that seem to be common for use as foliar sprays against the palm leaf pathogens are chlorothalonil, iprodione and mancozeb. These are contact fungicides, so uniform coverage of the foliage is essential. Always follow the label regarding pesticide use.
Q&A Library Searching Tips