Mule Palm Black Spots Problem!

[Phattydeluxe]

Hello Palm Talk fam! I already posted this on the Discussing Palms Worldwide Forum, but got a tip there may be more Mule Palm owners in this sub forum. So posting again here for visibility. Hope that's ok with the moderators! 😃

I have 3 Mule Palms (X Butiagrus nabonnandii) that have developed black spots on the spines (rachis?) of the fronds. They are only on the top side of the frond spines, not the underside, which makes me think it has something to do with the sun? They aren't really on the leaves, and more prominent toward the tip of each frond, not present from the petiole base to about mid way. The palms have looked green and otherwise healthy, however one palms new fronds coming from the center of the crown shaft has flopped over and is drooping. I thought the strong winds may have snapped it… but upon looking closer I noticed the black spots. Inspecting the other trees, I see they all have them… although they are the most pronounced on the tree with the drooping crown. Assuming the crown droop is related?

Can anyone help identify what this problem is? Is this a fungus? Too much water? Heat damage from the last 3 months of consistent 105+ degree weather here in Texas with no rain?

If it is indeed fungus, how should it be treated? A systemic drench of the roots? A topical spray? Copper? This is all new to me so please respond like I’m a 5th grader. lol Any details are appreciated!
 

Other relevant details:

Trees are in Houston, TX, and were planted in April. About 5’ - 6’ clear trunk size. Sprinklers in planter beds come on 3x per week for 6 mins each. Fertilized once with Palm gain in early summer. Heavy clay soil.

Thanks all!

[MarcusH]

49 minutes ago, Phattydeluxe said:

Hello Palm Talk fam! I already posted this on the Discussing Palms Worldwide Forum, but got a tip there may be more Mule Palm owners in this sub forum. So posting again here for visibility. Hope that's ok with the moderators! 😃

I have 3 Mule Palms (X Butiagrus nabonnandii) that have developed black spots on the spines (rachis?) of the fronds. They are only on the top side of the frond spines, not the underside, which makes me think it has something to do with the sun? They aren't really on the leaves, and more prominent toward the tip of each frond, not present from the petiole base to about mid way. The palms have looked green and otherwise healthy, however one palms new fronds coming from the center of the crown shaft has flopped over and is drooping. I thought the strong winds may have snapped it… but upon looking closer I noticed the black spots. Inspecting the other trees, I see they all have them… although they are the most pronounced on the tree with the drooping crown. Assuming the crown droop is related?

Can anyone help identify what this problem is? Is this a fungus? Too much water? Heat damage from the last 3 months of consistent 105+ degree weather here in Texas with no rain?

If it is indeed fungus, how should it be treated? A systemic drench of the roots? A topical spray? Copper? This is all new to me so please respond like I’m a 5th grader. lol Any details are appreciated!
 

Other relevant details:

Trees are in Houston, TX, and were planted in April. About 5’ - 6’ clear trunk size. Sprinklers in planter beds come on 3x per week for 6 mins each. Fertilized once with Palm gain in early summer. Heavy clay soil.

Thanks all!

Can you show us more pictures of that palm (trunk area) ? 

It certainly looks like a disease,  fungus . My first question did you cut anything off from that palm earlier ? Sometimes people don't sanitize their pruning sheers which also leads to transmitting diseases.  Just a guess from my side I'm sure others will chime in to give you more detailed information.  

[Phattydeluxe]

Thanks Marcus,

Yes, I have cut some lower fronds off of each of the 3 mules since planting them, and yes I’m guilty of not sanitizing the pruners.

Here are some additional pictures, showing the trunk and full canopy. The first few are from the tree that has it the worst, the last few are from the largest tree. All 3 trees have the black spots.

I also included a picture from the underside of the fronds… it’s curious that the spots are not visible there, and only are on the topside of the fronds. 

[Allen]

8 hours ago, Phattydeluxe said:

Is this only on older fronds and the newest 2-3 don't have this?

[scarecrow]

Read the Disease Management section. It applies for leaf and rachis blights as well. It may be helpful to get your local extension involved. https://edis.ifas.ufl.edu/publication/PP141

[Phattydeluxe]

16 hours ago, Allen said:

Is this only on older fronds and the newest 2-3 don't have this?

Hey Allen,

On the drooping tree that has this problem the worst, the newest fronds don’t have the spots at all yet. The pic below is of the 3rd or so newest frond. As you can see, there are the beginnings of some black spots. It’s definitely worse the older the frond is.

The bigger healthier tree only has the black spots on the oldest fronds, most of the fronds in the center do not have any of the black spots.

[Phattydeluxe]

[Phattydeluxe]

13 hours ago, scarecrow said:

Read the Disease Management section. It applies for leaf and rachis blights as well. It may be helpful to get your local extension involved. https://edis.ifas.ufl.edu/publication/PP141

Thanks for this! Reading it now.

[Allen]

28 minutes ago, Phattydeluxe said:

Hey Allen,

On the drooping tree that has this problem the worst, the newest fronds don’t have the spots at all yet. The pic below is of the 3rd or so newest frond. As you can see, there are the beginnings of some black spots. It’s definitely worse the older the frond is.

The bigger healthier tree only has the black spots on the oldest fronds, most of the fronds in the center do not have any of the black spots.

I don't think you have any big problem I have palms that do that on older fronds.  It might have had some damage to exasperate it

[Phattydeluxe]

On 10/9/2023 at 12:33 PM, Allen said:

I don't think you have any big problem I have palms that do that on older fronds.  It might have had some damage to exasperate it

Well that’s encouraging! Do you have any mules?

Still confused as to why the tree that has the most black spots also had the drooping new fronds. Seems possibly due to overwatering then? Maybe why the spots are worse on this tree too… I think it gets the most water. 

Still concerned this could be some sort of fungus… is there any risk by doing a fungicide treatment just to be sure?

Anyone have fungicide recommendations? I’m assuming a systemic root drench would be best?

[Allen]

Well that’s encouraging! Do you have any mules?

Mules in 7A Tennessee? https://www.palmtalk.org/forum/topic/76907-my-garden-over-the-years/

Still confused as to why the tree that has the most black spots also had the drooping new fronds. Seems possibly due to overwatering then? Maybe why the spots are worse on this tree too… I think it gets the most water. 

Are these palms newly planted this year?  I see they are all staked?  How and when exactly were they planted?  Were the holes amended?  Why is the drooping one roped around the top fronds near spear? Try to keep your sprinklers off the palm canopy.

Still concerned this could be some sort of fungus… is there any risk by doing a fungicide treatment just to be sure? Anyone have fungicide recommendations? I’m assuming a systemic root drench would be best?

You can spray everything with this one and it will be ok.  I can't recommend a systemic one - https://www.amazon.com/gp/product/B0052NL4FK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

I think this is just where the palms are starting to kill off the old fronds and sometimes the petiole is weaker/damaged and turns this black color before dying off.  If you had these palms recently installed (ie the last year) the roots are not established enough to support your palm canopy combined with less sun going into fall is what is going on.  Compare to my Trachycarpus fronds

Edited October 11, 2023 by Allen

[Phattydeluxe]

Thanks Allen!

Apologies for the late reply, been out of country. I enjoyed seeing your palms and garden in The Boro! I was up in Hendersonville for about 10 years and didn't dare try any palms. Fantastic to see what is possible there in 7a. Love all the other tropicals and elephant ears, cannas, etc you've done. Looks great.

I appreciate the feedback on my mules. Yes, the Palms in question were all planted this year in April. The trunks are all staked, and I staked in some additional rope around the new fronds coming from the center of the crown that were severely drooping in an attempt to keep them upright. Now that I have backed off the watering and the weather is milder, I think I can remove the rope as it seems to have strengthened up. In the few weeks since posting this the tree seems to be on the right track.

I haven't tried any fungicide, but may try an application just to be safe. However, looking at the picture from your palm, the black spots on the rachis may just be a natural phenomenon as they are dying out. The point you made about the newly planted trees not having enough established roots to support the amount of fronds makes a lot of sense and seems very plausible. The older fronds obviously have it the worst, and the newer fronds are looking ok.

You've definitely helped calm me down. Thank you sir!

Edited October 26, 2023 by Phattydeluxe