Coconut palm disease: what is it?

[Emarohl]

I have this juvenile cocos nucifera in a large pot outside. It sits in full sun on the southern side of my house. At first this little guy was thriving, but over the last few months it has developed these brownish yellow spots and necrotic tissue that continues to spread throughout the leaves. I noticed that it got worse over the rainy months during the summer, when it would sometimes rain multiple days in a row.  I live in Sarasota, FL right near the water (technically 9b but probably closer to 10a microclimate). It hasn’t been through winter yet so I know it’s not cold damage. I’m thinking maybe some sort of fungus?

Top and bottom pics were taken within the last 2 weeks. Middle pic was 2 months or so after planting in May 2022. I bought it from Home Depot in March. 
 

Any advice/recommendations would be much appreciated! 

Edited November 11, 2022 by Emarohl

[JLM]

Looks like it might be a nutrient deficiency of some sort. @Merlynhas a good guide to identifying the difference between each deficiency. 

Edit: After looking at some pics online of palms with potassium deficiency, they look similar to your palm. I would wait until others can comment though, i may be wrong.

Edited November 11, 2022 by JLM

[Merlyn]

@JLM yeah I'd think potassium deficiency too.  The browned and yellowed tips could be a bit of other stuff too.  At the size of that palm I think it's probably used up all the nutrients from the nut, so it needs some fertilizer.  I typically use Osmocote in pots.  Here's the list JLM was talking about:

• Nitrogen - Older fronds turn light green uniformly, new fronds remain dark green until deficiency is really severe
• Potassium - Older fronds get translucent yellow/orange or dead spots on leaves, especially at the tips. Caryota and Arenga get random splotched dead spots in leaves. Sometimes tips are curled or frizzled. Always starts at tips of oldest leaves, moving inwards
• Magnesium -Yellow linear bands on oldest leaves first, transitions to solid green at the base of each leaf. Never causes leaf tip necrosis
• Iron - Many times caused by overly mucky soil and root rot. Starts with new spear leaves with yellow-green or even white, possibly with spots of green.
• Manganese - Lengthwise necrotic streaks in leaves with dead and curled leaf tips. Similar to bands showing Magnesium deficiency
• Boron - Bent or necrotic or distorted leaf tips, distorted or bent spear, bands of dead spots on new fans, spears that won't fully open
• Water - Underwatering brown at the edges first, later followed by yellowing of the whole leaf. Overwatering can be drooping fronds turning yellowish and losing color
• Dolomitic Lime or Azomite - Magnesium Carbonate – reduces acidity/raises pH – slower release and adds Magnesium, helps avoid Potassium deficiencies in Cuban Copernicias. 5Lb per palm on full-size Copernicias and a bit less on Kentiopsis Oliviformis
• Garden Lime - Calcium Carbonate – fast release but works well. 5Lb per palm on full-size Copernicias and a bit less on Kentiopsis Oliviformis

[Emarohl]

Now that you mention it, it sure does seem to look like potassium deficiency. It’s planted in a mix of palm specific soil and our native sandy Florida soil, which I hear is known for lacking potassium.

I was planning on fertilizing this weekend with slow release granular fertilizer. I usually use miracle gro shake n feed specifically for palms as I’ve read good things about it. Should I supplement with anything else or will that be sufficient? Maybe some foliar spray? 

Thank you for the advice! 

[Emarohl]

It’s worth noting that I also fertilized this guy back in July. Maybe I didn’t add enough? 

[Merlyn]

@Emarohl it's probably better to fertilize more often with less amount.  I do 4x per year here, roughly February, May, August, November.  If you fertilized in July it's a good time for another dose.  My nursery area is smaller pots than yours, mostly 1g sizes.  I use Osmocote and a diluted spray of Miracle Gro.  I don't know anything about their Shake-n-Feed Palm, but the label looks reasonable.  I'd guess with all the rain in July-Aug-Sept that your fertilizer probably all washed out or was consumed by now.  The membrane-type fertilizers like Osmocote and Nutricote are nice because they feed continuously for months.  Standard granular could dissolve over a few weeks, and liquid ones could get washed out with the first torrential thunderstorm.

If it is a potassium deficiency, a good long-term solution is to add some Lanbeinite aka SulPoMag.  This is a good slow-dissolving mineral that has Magnesium and Potassium.  I've bought some and just started using it on a couple of palms.  It's supposed to be slow, so don't expect it to quickly fix anything.

Also, in case you didn't know, there's no "healing" a palm leaf with yellowing or dead spots or a browned tip.  Fertilizing now will make sure that deficiencies don't get worse, and that the next fronds come out looking nice.  The only ones that are "kinda" fixable are nitrogen and iron, which tend to cause fronds to look lighter green.  Adding fertilizer can help turn them a darker green.  But yellow and brown are permanent. 

[Emarohl]

Excellent, I will try all of this! 

[Than]

16 hours ago, Emarohl said:

Excellent, I will try all of this! 

Please let us know if it worked!

[sonoranfans]

yeah its a deficiency due to under fertilization.  4months since you last fertilized, 120 days is too long for anything except a controlled release membrane fertilizer like florikan or osmocote.  Even slow release wont make 90 days in florida wet season.  I would check the delivery specification of the fertilizer and if it doesnt have one, you are asking for trouble.  Potassium(K) is the first nutrient to go in all fertilizers except the membrane release fertilizers  I mentioned above.   It is readily washed away in rain without the membrane.  These damaged leaves wont recover but new ones will be without the deficiency.  Welcome to palmtalk!

[MelvinB]

To me it looks like a fungus instead of fertilizing issues. Soil stays too wet which can trigger fungus.