Soon after I started my nursery, I noticed king sagos that would have brown leaves on the new flush. I asked a few well known nursery owners what this was and all but one told me it was a fungus that gets on sagos. I would later find out that it was a minor element deficiency. After researching even further, I found out that it mainly came from a plant never being fertilized, or it occurred when the plant is growing in alkaline soils. The alkaline soil locks up certain minor elements which causes this problem. Upon experimenting, I found out that in most cases, the minor packages of fertilizers are not strong enough in these particular elements to take care of the problem. I have found that if the sagos are fertilized regularly with a product having a good minors package, a once a year application of extra minors will usually take care of the problem.
I have put together a proven remedy that in most cases will take care of sagos that have this problem. (Sometimes a plant that has had this problem for years is so weak that it can't be brought out of the decline, but that is only in extreme cases.) I was making a product I called Sago Supplement available but have had to take it off the shelf and I will probably not be able to make it available again, but I can at least explain what you can use to help your sagos. The key element is Manganese (which is not to be confused with Epsom Salts which is Magnesium). However, when certain elements are used at high concentrations, they can lock up other minor elements. There is a direct relationship between Manganese and Iron. There are many people who grow palms that have noticed their palms getting a Manganese deficiency after using a fertilizer high in Iron as the only added minor element. We would add enough Iron to help with this balance. We had derived our minor elements from Sulfates in particular so that this product will help lower the pH of the soil in cases where the pH is just above neutral. I had never seen a product that had these minors in it used for this purpose. If you go to the store and purchase Manganese Sulfate and Iron Sulfate, you can make the same thing. I would mix 4 parts Manganese Sulfate with 2 parts Iron Sulfate. (For the rest of this information, I will still call this Sago Supplement.) All you have to do is spread Sago Supplement around the stem of the sago, and water it in well. The next new leaves that are produced will come out looking normal. It takes a few weeks for Sago Supplement to work, so if by chance your sago produced leaves within a few days, then you may need to wait until the next flush. Typically a plant in this condition will not flush new leaves very quickly. I suggest using Cycad Special Growth and Coning Formula at the same time, which will normally produce new leaves much faster. Some people will cut off all the old leaves to help force out a new flush, but if the plant does not flush soon, this procedure can drain even more energy out of the plant. If one application does not work, I would take the time to check the pH in the soil. Your pH may be so alkaline that you may need to use a product specially made to lower the pH.