Cycad yellowing

[fiji jim]

Hi All,

In Fiji, in the last 15 years most of the Cycas circinalis and C. rumphii var seemannii, are in declining health.

I have posted pics in the hope that this problem can be defined and cured.

So any opinion and advice would be appreciated.

jim

[Merlyn]

@fiji jim has it been unusually hot, sunny and dry recently?  The Cycas do look a bit like sunburn, since the parts of the fronds sticking out into the sun are burned yellow and the base of the fronds are still healthy green.  I have a Cycas Wadei that looks almost exactly like your smaller bottom left one in the 2nd photo.  It looked great until the beginning of May, when it stopped raining and turned to 100+ for 3-4 weeks in a row.

The top bigger two look like they may have a Manganese deficiency.  The new fronds have that "frizzle top" look to them.  I give my Cycas all a handful of Manganese Sulfate every spring.  Mine is a hard granular type, about the size of a BB.

[fiji jim]

Thanks Merlyn,

This is not a seasonal thing. The time of year makes no difference and there is very little variation in temperatures throughout the year.

Many times in the last several years, I have defoliated them and fertilized heavily with a general fertilizer and insecticide and foliar nutrient sprays when they start to regrow.

As soon as a full head of leaves occurs, the yellowing starts. It is now difficult to find any cycad in Fiji that are not yellow.

The strange thing is that this never occurred before about 15 years ago and is observed everywhere in the country, regardless of soil type and other variables.

So I will search for a fertilizer heavy in manganese.

Thanks for your input.

jim

[Merlyn]

@fiji jim that's odd that they grow out green and then start yellowing.  But I guess I did see that on a Cyacas Revoluta x Debaoensis (probably Rev x Multifrondis) that just flushed in the front yard.  It looked a nice light green until it was *almost* finished and hardened off.  As it was hardening off it started showing spots of yellow.  "Frizzle top" is frequent on Revoluta around here, which is the only reason I know about Manganese deficiencies.  If the yellowing is a slow progression over weeks *after* the flush has completely hardened off, then it's probably not Manganese.  As I understand it, Manganese is not a "mobile" nutrient, so the plant can't steal it from old leaves to provide it to the new flush.  And Manganese is really only critical while the leaves are growing.  So Manganese deficiencies are only obvious during the flush.