Lethal Yellowing of Dyspis lutescens in Florida

[aabell]

I have this large clump of D lutescens in my side yard that has been slowly in decline since I move in a few years ago. I recently found some old Ganoderma cankers at the base and intend to remove the whole thing eventually but have been trying to determine the exact cause of the palms decline as they seem to be dying one by one from the top, and the fungus comes after. I did notice some of the old leaf bases harboring massive colonies of mealybugs but I've never heard of mealybugs killing a large outdoor palm before.

Today I noticed most of the leaves on one of the shorter stems suddenly had turned yellow, following the same pattern. Soon the whole top will rot off and nod over. Since it was at eye level I investigated and peeled back some of the leaf bases, noticing a bit of black and white sootiness, and then I spotted a few small yellow leaf hopper insects crawling around the outside. It's not something I have first hand experience with but now that I've researched it I think it's LY. 

I don't particularly care about this cluster but is this a known issue? Several websites list this species are LY resistant, and I was under the impression that the disease isn't as much of a problem as it used to be (why is that exactly?). There are approximately 10,000 other D. lutescens within a mile of here and I have noticed that they range from very healthy looking to much worse than this. The neighbors also have a huge screen of them that provides a lot of privacy for me as well and I would like to help them keep those healthy if I can. It seems like an ideal host plant, since they can kill one stem and just move on to the next. Is there anything I can do?

Edited January 4, 2022 by aabell

[bubba]

Got to be Ganoderma. No way LY. Dl’s are mosquito breeding grounds. You usually cannot kill them with flamethrowers.

[Merlyn]

My gut feel is that it's not LY.  That swept through and basically killed off all the susceptible palms.  The ones that survived are partially or mostly resistant, which is why you don't hear too much about LY anymore.  Now of course it's LB (Lethal Bronzing) which is somewhat related and the symptoms are visually somewhat similar.  I don't think it's either in your case. 

My guess is that Ganoderma is attacking the lower part of the trunk, which cuts off nutrients and water to the top.  Then the top dies off.  The one distinctive feature on Ganoderma is that it does not cause a "soft rot" so it doesn't turn mushy.  The upper trunks turning mushy and falling over looks more like a Thielaviopsis infection, which rots out the crown of palms and can cause them to just fall over like yours.  Here's the two info pages on UFL's website:

https://edis.ifas.ufl.edu/publication/PP100

https://edis.ifas.ufl.edu/publication/PP143

I don't see the telltale signs of "trunk bleeding" for Thielaviopsis, but if the upper trunks are just a stringy brown mess inside...that's probably it.  This was an Adonidia triple that I removed, which looked like it had Thielaviopsis.  I dug out the "stump" and trashed the whole thing, then treated nearby palms with Banrot.  So far (fingers crossed) it has not spread over the past 14 months.

 

[aabell]

5 minutes ago, Merlyn said:

My gut feel is that it's not LY.  That swept through and basically killed off all the susceptible palms.  The ones that survived are partially or mostly resistant, which is why you don't hear too much about LY anymore.  Now of course it's LB (Lethal Bronzing) which is somewhat related and the symptoms are visually somewhat similar.  I don't think it's either in your case. 

My guess is that Ganoderma is attacking the lower part of the trunk, which cuts off nutrients and water to the top.  Then the top dies off.  The one distinctive feature on Ganoderma is that it does not cause a "soft rot" so it doesn't turn mushy.  The upper trunks turning mushy and falling over looks more like a Thielaviopsis infection, which rots out the crown of palms and can cause them to just fall over like yours.  Here's the two info pages on UFL's website:

https://edis.ifas.ufl.edu/publication/PP100

https://edis.ifas.ufl.edu/publication/PP143

I don't see the telltale signs of "trunk bleeding" for Thielaviopsis, but if the upper trunks are just a stringy brown mess inside...that's probably it.  This was an Adonidia triple that I removed, which looked like it had Thielaviopsis.  I dug out the "stump" and trashed the whole thing, then treated nearby palms with Banrot.  So far (fingers crossed) it has not spread over the past 14 months.

 

Good info thanks. Here's the photo I couldn't find before showing the mealybug problem as well. Could the mealys be providing an entry point for Thielaviopsis if they aren't outright killing it?

I guess I don't understand how Ganoderma works if that is the main culprit. It's one of those huge raised root masses 5'+ in diameter. Tons of vigorous sprouts from the base, all around the dead canes. Plenty of alive canes 20' tall still. But every few months one of them rots out at the top and then takes a long time to fully decay from there. The Ganoderma pops up periodically only at the very base of the north side where it's fully shaded, nestled against plenty of healthy living tissue. But I do understand that where there is a conch, the whole root system is infected.

paging @NOT A TA

In any case it seems like the palm isn't healthy and needs to come out.

 

[Silas_Sancona]

27 minutes ago, aabell said:

Good info thanks. Here's the photo I couldn't find before showing the mealybug problem as well. Could the mealys be providing an entry point for Thielaviopsis if they aren't outright killing it?

I guess I don't understand how Ganoderma works if that is the main culprit. It's one of those huge raised root masses 5'+ in diameter. Tons of vigorous sprouts from the base, all around the dead canes. Plenty of alive canes 20' tall still. But every few months one of them rots out at the top and then takes a long time to fully decay from there. The Ganoderma pops up periodically only at the very base of the north side where it's fully shaded, nestled against plenty of healthy living tissue. But I do understand that where there is a conch, the whole root system is infected.

paging @NOT A TA

In any case it seems like the palm isn't healthy and needs to come out.

 

Don't think the Mealy Bugs would transfer Ganoderma.. Fairly sure spores shed by the fungal conks move through the soil / air.  The mealys ( ...and other " Bad " bugs ) will often take full advantage of a stressed out plant however ( Stressed by the fungus / other issues perhaps ..in other cases ) ..Increased issues w/ them are often a pretty good sign something is wrong w/ the plant.

[Merlyn]

@aabell that's why i was guessing at Thielaviopsis as the primary killer.  Ganoderma attacks lignin tissue, which is the strong stringy fibers.  Thielaviopsis attacks the softer tissues, and frequently is found in the middle to top.  If the trunk tops are brown and stringy inside, I would guess Thielaviopsis is the main killer.  But it could easily be both...

Also, Ganoderma doesn"t affect small palms, because they don"t have much lignin tissue.  

[NOT A TA]

I saw this thread this morning and thought I'd posted questions but apparently not.

On 1/4/2022 at 11:19 AM, aabell said:

Several websites list this species are LY resistant, and I was under the impression that the disease isn't as much of a problem as it used to be (why is that exactly?).

During the height of the lethal yellowing problem a lot of palms were lost which increased the distance between palms reducing the likelihood that plant hoppers would have lunch on one and dinner on another so as the susceptible palm population dwindled transmission became less and less likely. Also, if there was an environmental period that interrupted the life cycle of the hopper such as a cold or dry period then with less insects feeding, transmission would also have been reduced.  Nature tends to balance itself over time. I'm curious what insects you've got besides the mealybugs. At the bottom of this article there is a link to Brian Bahders website where you can get sticky traps to collect insects (intended for leaf hoppers) and send them in for identification.

9 hours ago, aabell said:

Could the mealys be providing an entry point for Thielaviopsis if they aren't outright killing it?

Unlikely I think but perhaps possible?  Thielaviopsis is usually taken from an infected plant and enters an unaffected plant through a wound. Seems to occur most often by pruning tools and woodpeckers.

8 hours ago, Silas_Sancona said:

  The mealys ( ...and other " Bad " bugs ) will often take full advantage of a stressed out plant however ( Stressed by the fungus / other issues perhaps ..in other cases ) ..Increased issues w/ them are often a pretty good sign something is wrong w/ the plant.

This ^^^ which leads me to ask how much water does the clump get? When the plant is a small clump in a 2-3 gallon pot it only needs X amount of water. When the clump is mature it needs a LOT more water. If it doesn't get enough the old ones in the center on the top of the root mound start to die off (my observations). My next door neighbor had a clump like that right on the other side of the fence where my potting bench is. I offered to thin out the clump by removing about 10 large old stems with my chainsaw, meanwhile, he increased the irrigation in that area and the clump has looked good for the past several years.

It would be interesting to see what the inside of the stems look like when you cut out the ones currently dying. As @Merlyn noted, Thielaviopsis discolors the woody tissue and in extreme cases tops tilt over and the tissue gets nasty looking.

The Ganoderma zonatum is a natural, normal, decay fungus that breaks down palm tissue. It's spores are everywhere in S FL so there's not much point in trying to "cleanse" the area of it, even when you eventually remove the clump. It's growing because there's dead palm tissue to grow on and although Ganoderma might possibly be able to infect a healthy palm there is no scientific proof that it can or does occur that I'm aware of. However it often appears as a secondary infection on a dead/dying palm. I see it most often on Queens with thielaviopsis. The basidiocarps form (or increase in size) when the environmental conditions are favorable so while it might seem like the new white rings appear randomly they do so only when conditions are favorable. I've been able to initiate growth of them and new rings on them while others I'm observing are not showing the same signs just by increasing humidity and /or shade during certain temperatures.

Unlike many regular trees, palm roots don't graft themselves to one another. So just because one stem and any of it's suckers may share roots, a disease isn't automatically shared with all the other stems in the Dypsis clump. And, while a stem stump may have a Ganoderma basidiocarp that doesn't necessarily mean a healthy stem next to it is doomed. I've been observing Ganoderma zonatum on stumps from thinning in Dypsis lutescens clumps for a few years now where the Ganoderma doesn't seem to infect healthy stems. I'm also trying to infect healthy palms of different types with Ganoderma with no success so far.

How high above the soil line are the base of the stems that are dying off?

Water other than rain?

Any changes in the topography that would have affected drainage in the area?

Lawn surrounding the clump?

Mulch around the clump?

Weed killers used in the area?

[aabell]

12 hours ago, NOT A TA said:

I saw this thread this morning and thought I'd posted questions but apparently not.

During the height of the lethal yellowing problem a lot of palms were lost which increased the distance between palms reducing the likelihood that plant hoppers would have lunch on one and dinner on another so as the susceptible palm population dwindled transmission became less and less likely. Also, if there was an environmental period that interrupted the life cycle of the hopper such as a cold or dry period then with less insects feeding, transmission would also have been reduced.  Nature tends to balance itself over time. I'm curious what insects you've got besides the mealybugs. At the bottom of this article there is a link to Brian Bahders website where you can get sticky traps to collect insects (intended for leaf hoppers) and send them in for identification.

Unlikely I think but perhaps possible?  Thielaviopsis is usually taken from an infected plant and enters an unaffected plant through a wound. Seems to occur most often by pruning tools and woodpeckers.

This ^^^ which leads me to ask how much water does the clump get? When the plant is a small clump in a 2-3 gallon pot it only needs X amount of water. When the clump is mature it needs a LOT more water. If it doesn't get enough the old ones in the center on the top of the root mound start to die off (my observations). My next door neighbor had a clump like that right on the other side of the fence where my potting bench is. I offered to thin out the clump by removing about 10 large old stems with my chainsaw, meanwhile, he increased the irrigation in that area and the clump has looked good for the past several years.

It would be interesting to see what the inside of the stems look like when you cut out the ones currently dying. As @Merlyn noted, Thielaviopsis discolors the woody tissue and in extreme cases tops tilt over and the tissue gets nasty looking.

The Ganoderma zonatum is a natural, normal, decay fungus that breaks down palm tissue. It's spores are everywhere in S FL so there's not much point in trying to "cleanse" the area of it, even when you eventually remove the clump. It's growing because there's dead palm tissue to grow on and although Ganoderma might possibly be able to infect a healthy palm there is no scientific proof that it can or does occur that I'm aware of. However it often appears as a secondary infection on a dead/dying palm. I see it most often on Queens with thielaviopsis. The basidiocarps form (or increase in size) when the environmental conditions are favorable so while it might seem like the new white rings appear randomly they do so only when conditions are favorable. I've been able to initiate growth of them and new rings on them while others I'm observing are not showing the same signs just by increasing humidity and /or shade during certain temperatures.

Unlike many regular trees, palm roots don't graft themselves to one another. So just because one stem and any of it's suckers may share roots, a disease isn't automatically shared with all the other stems in the Dypsis clump. And, while a stem stump may have a Ganoderma basidiocarp that doesn't necessarily mean a healthy stem next to it is doomed. I've been observing Ganoderma zonatum on stumps from thinning in Dypsis lutescens clumps for a few years now where the Ganoderma doesn't seem to infect healthy stems. I'm also trying to infect healthy palms of different types with Ganoderma with no success so far.

How high above the soil line are the base of the stems that are dying off?

Water other than rain?

Any changes in the topography that would have affected drainage in the area?

Lawn surrounding the clump?

Mulch around the clump?

Weed killers used in the area?

Good information thank you. Water other than rain? No, I don't irrigate the lawn or any mature trees. But that gets at another possibility I hadn't mentioned - it's in too much shade. It's boxed in to the west by a live oak and the south by a fast growing Peltophorum, so it only really gets morning sun, and the Peltophorum takes a little more away each year. I checked carefully again today and I don't see any active Ganoderma basidiocarps. The area around the base of the clump falls under the live oak canopy, is mulched with oak leaves, and is free of grass or any other vegetation. Is not actively maintained other than my occasional weed eating around the sidewalk.

What I did notice today is that many of the dead/dying canes radiate from one area in the root mound - near the south side. (marked with Xs in one of the photos below) It is not particularly raised, in fact it's a bit of depression in the clump that has accumulated years worth of leaf litter, and the roots of the canes in this area are not exposed like those higher up or on the sides of the clump. Maybe there is a fungal/root rot issue from water sitting in this area?

A few months ago I cleaned trapped debris out of the center of the cluster and also trimmed quite a few small offsets. This was after I noticed the decline in an effort to improve its health and to better see what was going on. But before I did there was many years worth of dead fronds and leaves sitting in the center.

I broke up this small dying cane today to investigate. (It was an interesting doubly-forked one that I liked a lot). I didn't see anything partiulary nasty, but it easily snapped when I bent it, seemed soft, weak and juicy but not dark brown or black yet. More ants farming mealybugs under the outer fronds but no other insects that I noticed.

I greatly appreciate the help. Like I said I don't care if I lose this palm but I am trying to better understand why it's happening because my neighbor has a beautiful screen of them that I'd like to help maintain if I can. Also just good information to have for the palms I'm planting myself elsewhere in the yard. 

Edited January 6, 2022 by aabell

[NOT A TA]

1 hour ago, aabell said:

Maybe there is a fungal/root rot issue from water sitting in this area?

I doubt it. The area looks too dry for the size/age of the clump. It takes a lot of water to sustain that much foliage. There isn't even enough moisture to allow weeds to grow.

I missed the power lines in the pic in the opening post. Many palms are affected by them however I'm not familiar with whether Dypsis lutescens is, might be part of the problem. Perhaps someone with more experience on that will chime in.

I doubt shade is much of an issue looking at the pics in your last post.

Looks to me like too much plant for the amount of water.

If it were mine and I wanted to keep it, I'd remove about 1/2 of the large stems taking out the oldest tallest ones first. Then leave only 2-3 that are 10' tall and 3-5 that are 4-5' tall and a couple small suckers or seedlings. Then as a clump it would be healthier and look better on rainfall only. Ideally it would like more water during the dry season, it looks like it's outgrown the available water supply.

1 hour ago, aabell said:

I don't see any active Ganoderma basidiocarps.

Conditions aren't usually favorable for new conk initiation or new rings on old conks this time of year. The Ganoderma is still actively growing on dead tissue in the clump, although perhaps at a slower rate than other times of the year.